Patent Publication Number: US-7901050-B2

Title: Printhead integrated circuit with suspended heater elements

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. application Ser. No. 12/205,908 filed Sep. 7, 2008, now issued U.S. Pat. No. 7,594,713, which is a Continuation of U.S. application Ser. No. 11/961,712 filed on Dec. 20, 2007, now issued U.S. Pat. No. 7,441,879, which is a Continuation of U.S. application Ser. No. 11/097,267 filed on Apr. 4, 2005, now U.S. Pat. No. 7,328,976, all of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of inkjet printers and discloses an inkjet printing system using printheads manufactured with micro-electromechanical systems (MEMS) techniques. 
     CO-PENDING APPLICATIONS 
     The following application has been filed by the Applicant simultaneously with the present application:
         U.S. Pat. No. 7,344,226       

     The disclosure of this co-pending application is incorporated herein by reference. 
     CROSS REFERENCES TO RELATED APPLICATIONS 
     The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
             
            
               
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     BACKGROUND OF THE INVENTION 
     Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc. 
     In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature. 
     Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988). 
     Ink Jet printers themselves come in many different types. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing. 
     U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous inkjet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al) 
     Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the inkjet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element. 
     Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. 
     As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables. 
     In the construction of any inkjet printing system, there are a considerable number of important factors which must be traded off against one another especially as large scale printheads are constructed, especially those of a pagewidth type. A number of these factors are outlined in the following paragraphs. 
     Firstly, inkjet printheads are normally constructed utilizing micro-electromechanical systems (MEMS) techniques. As such, they tend to rely upon standard integrated circuit construction/fabrication techniques of depositing planar layers on a silicon wafer and etching certain portions of the planar layers. Within silicon circuit fabrication technology, certain techniques are better known than others. For example, the techniques associated with the creation of CMOS circuits are likely to be more readily used than those associated with the creation of exotic circuits including ferroelectrics, galium arsenide etc. Hence, it is desirable, in any MEMS constructions, to utilize well proven semi-conductor fabrication techniques which do not require any “exotic” processes or materials. Of course, a certain degree of trade off will be undertaken in that if the advantages of using the exotic material far out weighs its disadvantages then it may become desirable to utilize the material anyway. However, if it is possible to achieve the same, or similar, properties using more common materials, the problems of exotic materials can be avoided. 
     A desirable characteristic of inkjet printheads would be a hydrophobic nozzle (front) face, preferably in combination with hydrophilic nozzle chambers and ink supply channels. This combination is optimal for ink ejection. Moreover, a hydrophobic front face minimizes the propensity for ink to flood across the front face of the printhead. With a hydrophobic front face, the aqueous inkjet ink is less likely to flood sideways out of the nozzle openings and more likely to form spherical, ejectable microdroplets. 
     However, whilst hydrophobic front faces and hydrophilic ink chambers are desirable, there is a major problem in fabricating such printheads by MEMS techniques. The final stage of MEMS printhead fabrication is typically ashing of photoresist using an oxygen plasma. However, any organic, hydrophobic material deposited onto the front face will typically be removed by the ashing process to leave a hydrophilic surface. Accordingly, the deposition of hydrophobic material needs to occur after ashing. However, a problem with post-ashing deposition of hydrophobic materials is that the hydrophobic material will be deposited inside nozzle chambers as well as on the front face of the printhead. With no photoresist to protect the nozzle chambers, the nozzle chamber walls become hydrophobized, which is highly undesirable in terms of generating a positive ink pressure biased towards the nozzle chambers. This is a conundrum, which has to date not been addressed in printhead fabrication. 
     Accordingly, it would be desirable to provide a printhead fabrication process, in which the resultant printhead chip has improved surface characteristics, without comprising the surface characteristics of nozzle chambers. It would further be desirable to provide a printhead fabrication process, in which the resultant printhead chip has a hydrophobic front face in combination with hydrophilic nozzle chambers. 
     SUMMARY OF THE INVENTION 
     In a first aspect, there is provided a printhead comprising a plurality of nozzles formed on a substrate, each nozzle comprising a nozzle chamber, a nozzle opening defined in a roof of the nozzle chamber and an actuator for ejecting ink through the nozzle opening, wherein at least part of an ink ejection face of the printhead is hydrophobic relative to the inside surfaces of each nozzle chamber. 
     In a second aspect, there is provided a method of hydrophobizing an ink ejection face of a printhead, whilst avoiding hydrophobizing nozzle chambers and/or ink supply channels, the method comprising the steps of: 
     (a) filling nozzle chambers on the printhead with a liquid; and 
     (b) depositing a hydrophobizing material onto the ink ejection face of the printhead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Notwithstanding any other forms that may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic cross-sectional view through an ink chamber of a unit cell of a printhead according to an embodiment using a bubble forming heater element; 
         FIG. 2  is a schematic cross-sectional view through the ink chamber  FIG. 1 , at another stage of operation; 
         FIG. 3  is a schematic cross-sectional view through the ink chamber  FIG. 1 , at yet another stage of operation; 
         FIG. 4  is a schematic cross-sectional view through the ink chamber  FIG. 1 , at yet a further stage of operation; and 
         FIG. 5  is a diagrammatic cross-sectional view through a unit cell of a printhead in accordance with an embodiment of the invention showing the collapse of a vapor bubble. 
         FIG. 6  is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 
         FIG. 7  is a schematic, partially cut away, exploded perspective view of the unit cell of  FIG. 6 . 
         FIG. 8  is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 
         FIG. 9  is a schematic, partially cut away, exploded perspective view of the unit cell of  FIG. 8 . 
         FIG. 10  is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 
         FIG. 11  is a schematic, partially cut away, exploded perspective view of the unit cell of  FIG. 10 . 
         FIG. 12  is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 
         FIG. 13  is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 
         FIG. 14  is a schematic, partially cut away, exploded perspective view of the unit cell of  FIG. 13 . 
         FIGS. 15 to 25  are schematic perspective views of the unit cell shown in  FIGS. 13 and 14 , at various successive stages in the production process of the printhead. 
         FIG. 26  shows partially cut away schematic perspective views of the unit cell of  FIG. 25 . 
         FIG. 27  shows the unit cell of  FIG. 25  primed with a fluid. 
         FIG. 28  shows the unit cell of  FIG. 27  with a hydrophobic coating on the nozzle plate. 
     
    
    
     DESCRIPTION OF OPTIONAL EMBODIMENTS 
     Bubble Forming Heater Element Actuator 
     With reference to  FIGS. 1 to 4 , the unit cell  1  of a printhead according to an embodiment of the invention comprises a nozzle plate  2  with nozzles  3  therein, the nozzles having nozzle rims  4 , and apertures  5  extending through the nozzle plate. The nozzle plate  2  is plasma etched from a silicon nitride structure which is deposited, by way of chemical vapor deposition (CVD), over a sacrificial material which is subsequently etched. 
     The printhead also includes, with respect to each nozzle  3 , side walls  6  on which the nozzle plate is supported, a chamber  7  defined by the walls and the nozzle plate  2 , a multi-layer substrate  8  and an inlet passage  9  extending through the multi-layer substrate to the far side (not shown) of the substrate. A looped, elongate heater element  10  is suspended within the chamber  7 , so that the element is in the form of a suspended beam. The printhead as shown is a microelectromechanical system (MEMS) structure, which is formed by a lithographic process which is described in more detail below. 
     When the printhead is in use, ink  11  from a reservoir (not shown) enters the chamber  7  via the inlet passage  9 , so that the chamber fills to the level as shown in  FIG. 1 . Thereafter, the heater element  10  is heated for somewhat less than 1 microsecond, so that the heating is in the form of a thermal pulse. It will be appreciated that the heater element  10  is in thermal contact with the ink  11  in the chamber  7  so that when the element is heated, this causes the generation of vapor bubbles  12  in the ink. Accordingly, the ink  11  constitutes a bubble forming liquid.  FIG. 1  shows the formation of a bubble  12  approximately 1 microsecond after generation of the thermal pulse, that is, when the bubble has just nucleated on the heater elements  10 . It will be appreciated that, as the heat is applied in the form of a pulse, all the energy necessary to generate the bubble  12  is to be supplied within that short time. 
     When the element  10  is heated as described above, the bubble  12  forms along the length of the element, this bubble appearing, in the cross-sectional view of  FIG. 1 , as four bubble portions, one for each of the element portions shown in cross section. 
     The bubble  12 , once generated, causes an increase in pressure within the chamber  7 , which in turn causes the ejection of a drop  16  of the ink  11  through the nozzle  3 . The rim  4  assists in directing the drop  16  as it is ejected, so as to minimize the chance of drop misdirection. 
     The reason that there is only one nozzle  3  and chamber  7  per inlet passage  9  is so that the pressure wave generated within the chamber, on heating of the element  10  and forming of a bubble  12 , does not affect adjacent chambers and their corresponding nozzles. The pressure wave generated within the chamber creates significant stresses in the chamber wall. Forming the chamber from an amorphous ceramic such as silicon nitride, silicon dioxide (glass) or silicon oxynitride, gives the chamber walls high strength while avoiding the use of material with a crystal structure. Crystalline defects can act as stress concentration points and therefore potential areas of weakness and ultimately failure. 
       FIGS. 2 and 3  show the unit cell  1  at two successive later stages of operation of the printhead. It can be seen that the bubble  12  generates further, and hence grows, with the resultant advancement of ink  11  through the nozzle  3 . The shape of the bubble  12  as it grows, as shown in  FIG. 3 , is determined by a combination of the inertial dynamics and the surface tension of the ink  11 . The surface tension tends to minimize the surface area of the bubble  12  so that, by the time a certain amount of liquid has evaporated, the bubble is essentially disk-shaped. 
     The increase in pressure within the chamber  7  not only pushes ink  11  out through the nozzle  3 , but also pushes some ink back through the inlet passage  9 . However, the inlet passage  9  is approximately 200 to 300 microns in length, and is only approximately 16 microns in diameter. Hence there is a substantial viscous drag. As a result, the predominant effect of the pressure rise in the chamber  7  is to force ink out through the nozzle  3  as an ejected drop  16 , rather than back through the inlet passage  9 . 
     Turning now to  FIG. 4 , the printhead is shown at a still further successive stage of operation, in which the ink drop  16  that is being ejected is shown during its “necking phase” before the drop breaks off. At this stage, the bubble  12  has already reached its maximum size and has then begun to collapse towards the point of collapse  17 , as reflected in more detail in  FIG. 21 . 
     The collapsing of the bubble  12  towards the point of collapse  17  causes some ink  11  to be drawn from within the nozzle  3  (from the sides  18  of the drop), and some to be drawn from the inlet passage  9 , towards the point of collapse. Most of the ink  11  drawn in this manner is drawn from the nozzle  3 , forming an annular neck  19  at the base of the drop  16  prior to its breaking off. 
     The drop  16  requires a certain amount of momentum to overcome surface tension forces, in order to break off. As ink  11  is drawn from the nozzle  3  by the collapse of the bubble  12 , the diameter of the neck  19  reduces thereby reducing the amount of total surface tension holding the drop, so that the momentum of the drop as it is ejected out of the nozzle is sufficient to allow the drop to break off. 
     When the drop  16  breaks off, cavitation forces are caused as reflected by the arrows  20 , as the bubble  12  collapses to the point of collapse  17 . It will be noted that there are no solid surfaces in the vicinity of the point of collapse  17  on which the cavitation can have an effect. 
     Features and Advantages of Further Embodiments 
       FIGS. 6 to 29  show further embodiments of unit cells  1  for thermal inkjet printheads, each embodiment having its own particular functional advantages. These advantages will be discussed in detail below, with reference to each individual embodiment. For consistency, the same reference numerals are used in  FIGS. 6 to 29  to indicate corresponding components. 
     Referring to  FIGS. 6 and 7 , the unit cell  1  shown has the chamber  7 , ink supply passage  32  and the nozzle rim  4  positioned mid way along the length of the unit cell  1 . As best seen in  FIG. 7 , the drive circuitry  22  is partially on one side of the chamber  7  with the remainder on the opposing side of the chamber. The drive circuitry  22  controls the operation of the heater  14  through vias in the integrated circuit metallisation layers of the interconnect  23 . The interconnect  23  has a raised metal layer on its top surface. Passivation layer  24  is formed in top of the interconnect  23  but leaves areas of the raised metal layer exposed. Electrodes  15  of the heater  14  contact the exposed metal areas to supply power to the element  10 . 
     Alternatively, the drive circuitry  22  for one unit cell is not on opposing sides of the heater element that it controls. All the drive circuitry  22  for the heater  14  of one unit cell is in a single, undivided area that is offset from the heater. That is, the drive circuitry  22  is partially overlaid by one of the electrodes  15  of the heater  14  that it is controlling, and partially overlaid by one or more of the heater electrodes  15  from adjacent unit cells. In this situation, the center of the drive circuitry  22  is less than 200 microns from the center of the associate nozzle aperture  5 . In most Memjet printheads of this type, the offset is less than 100 microns and in many cases less than 50 microns, preferably less than 30 microns. 
     Configuring the nozzle components so that there is significant overlap between the electrodes and the drive circuitry provides a compact design with high nozzle density (nozzles per unit area of the nozzle plate  2 ). This also improves the efficiency of the printhead by shortening the length of the conductors from the circuitry to the electrodes. The shorter conductors have less resistance and therefore dissipate less energy. 
     The high degree of overlap between the electrodes  15  and the drive circuitry  22  also allows more vias between the heater material and the CMOS metalization layers of the interconnect  23 . As best shown in  FIGS. 14 and 15 , the passivation layer  24  has an array of vias to establish an electrical connection with the heater  14 . More vias lowers the resistance between the heater electrodes  15  and the interconnect layer  23  which reduces power losses. However, the passivation layer  24  and electrodes  15  may also be provided without vias in order to simplify the fabrication process. 
     In  FIGS. 8 and 9 , the unit cell  1  is the same as that of  FIGS. 6 and 7  apart from the heater element  10 . The heater element  10  has a bubble nucleation section  158  with a smaller cross section than the remainder of the element. The bubble nucleation section  158  has a greater resistance and heats to a temperature above the boiling point of the ink before the remainder of the element  10 . The gas bubble nucleates at this region and subsequently grows to surround the rest of the element  10 . By controlling the bubble nucleation and growth, the trajectory of the ejected drop is more predictable. 
     The heater element  10  is configured to accommodate thermal expansion in a specific manner. As heater elements expand, they will deform to relieve the strain. Elements such as that shown in  FIGS. 6 and 7  will bow out of the plane of lamination because its thickness is the thinnest cross sectional dimension and therefore has the least bending resistance. Repeated bending of the element can lead to the formation of cracks, especially at sharp corners, which can ultimately lead to failure. The heater element  10  shown in  FIGS. 8 and 9  is configured so that the thermal expansion is relieved by rotation of the bubble nucleation section  158 , and slightly splaying the sections leading to the electrodes  15 , in preference to bowing out of the plane of lamination. The geometry of the element is such that miniscule bending within the plane of lamination is sufficient to relieve the strain of thermal expansion, and such bending occurs in preference to bowing. This gives the heater element greater longevity and reliability by minimizing bend regions, which are prone to oxidation and cracking. 
     Referring to  FIGS. 10 and 11 , the heater element  10  used in this unit cell  1  has a serpentine or ‘double omega’ shape. This configuration keeps the gas bubble centered on the axis of the nozzle. A single omega is a simple geometric shape which is beneficial from a fabrication perspective. However the gap  159  between the ends of the heater element means that the heating of the ink in the chamber is slightly asymmetrical. As a result, the gas bubble is slightly skewed to the side opposite the gap  159 . This can in turn affect the trajectory of the ejected drop. The double omega shape provides the heater element with the gap  160  to compensate for the gap  159  so that the symmetry and position of the bubble within the chamber is better controlled and the ejected drop trajectory is more reliable. 
       FIG. 12  shows a heater element  10  with a single omega shape. As discussed above, the simplicity of this shape has significant advantages during lithographic fabrication. It can be a single current path that is relatively wide and therefore less affected by any inherent inaccuracies in the deposition of the heater material. The inherent inaccuracies of the equipment used to deposit the heater material result in variations in the dimensions of the element. However, these tolerances are fixed values so the resulting variations in the dimensions of a relatively wide component are proportionally less than the variations for a thinner component. It will be appreciated that proportionally large changes of components dimensions will have a greater effect on their intended function. Therefore the performance characteristics of a relatively wide heater element are more reliable than a thinner one. 
     The omega shape directs current flow around the axis of the nozzle aperture  5 . This gives good bubble alignment with the aperture for better ejection of drops while ensuring that the bubble collapse point is not on the heater element  10 . As discussed above, this avoids problems caused by cavitation. 
     Referring to  FIGS. 13 to 26 , another embodiment of the unit cell  1  is shown together with several stages of the etching and deposition fabrication process. In this embodiment, the heater element  10  is suspended from opposing sides of the chamber. This allows it to be symmetrical about two planes that intersect along the axis of the nozzle aperture  5 . This configuration provides a drop trajectory along the axis of the nozzle aperture  5  while avoiding the cavitation problems discussed above. 
     Fabrication Process 
     In the interests of brevity, the fabrication stages have been shown for the unit cell of  FIG. 13  only (see  FIGS. 15 to 25 ). It will be appreciated that the other unit cells will use the same fabrication stages with different masking. 
     Referring to  FIG. 15 , there is shown the starting point for fabrication of the thermal inkjet nozzle shown in  FIG. 13 . CMOS processing of a silicon wafer provides a silicon substrate  21  having drive circuitry  22 , and an interlayer dielectric (“interconnect”)  23 . The interconnect  23  comprises four metal layers, which together form a seal ring for the inlet passage  9  to be etched through the interconnect. The top metal layer  26 , which forms an upper portion of the seal ring, can be seen in  FIG. 15 . The metal seal ring prevents ink moisture from seeping into the interconnect  23  when the inlet passage  9  is filled with ink. 
     A passivation layer  24  is deposited onto the top metal layer  26  by plasma-enhanced chemical vapour deposition (PECVD). After deposition of the passivation layer  24 , it is etched to define a circular recess, which forms parts of the inlet passage  9 . At the same as etching the recess, a plurality of vias  50  are also etched, which allow electrical connection through the passivation layer  24  to the top metal layer  26 . The etch pattern is defined by a layer of patterned photoresist (not shown), which is removed by O 2  ashing after the etch. 
     Referring to  FIG. 16 , in the next fabrication sequence, a layer of photoresist is spun onto the passivation later  24 . The photoresist is exposed and developed to define a circular opening. With the patterned photoresist  51  in place, the dielectric interconnect  23  is etched as far as the silicon substrate  21  using a suitable oxide-etching gas chemistry (e.g. O 2 /C 4 F 8 ). Etching through the silicon substrate is continued down to about 20 microns to define a front ink hole  52 , using a suitable silicon-etching gas chemistry (e.g. ‘Bosch etch’). The same photoresist mask  51  can be used for both etching steps.  FIG. 17  shows the unit cell after etching the front ink hole  52  and removal of the photoresist  51 . 
     Referring to  FIG. 18 , in the next stage of fabrication, the front ink hole  52  is plugged with photoresist to provide a front plug  53 . At the same time, a layer of photoresist is deposited over the passivation layer  24 . This layer of photoresist is exposed and developed to define a first sacrificial scaffold  54  over the front plug  53 , and scaffolding tracks  35  around the perimeter of the unit cell. The first sacrificial scaffold  54  is used for subsequent deposition of heater material  38  thereon and is therefore formed with a planar upper surface to avoid any buckling in the heater element (see heater element  10  in  FIG. 13 ). The first sacrificial scaffold  54  is UV cured and hardbaked to prevent reflow of the photoresist during subsequent high-temperature deposition onto its upper surface. 
     Importantly, the first sacrificial scaffold  54  has sloped or angled side faces  55 . These angled side faces  55  are formed by adjusting the focusing in the exposure tool (e.g. stepper) when exposing the photoresist. The sloped side faces  55  advantageously allow heater material  38  to be deposited substantially evenly over the first sacrificial scaffold  54 . 
     Referring to  FIG. 19 , the next stage of fabrication deposits the heater material  38  over the first sacrificial scaffold  54 , the passivation layer  24  and the perimeter scaffolding tracks  35 . The heater material  38  is typically a monolayer of TiAlN. However, the heater material  38  may alternatively comprise TiAlN sandwiched between upper and lower passivating materials, such as tantalum or tantalum nitride. Passivating layers on the heater element  10  minimize corrosion of the and improve heater longevity. 
     Referring to  FIG. 20 , the heater material  38  is subsequently etched down to the first sacrificial scaffold  54  to define the heater element  10 . At the same time, contact electrodes  15  are defined on either side of the heater element  10 . The electrodes  15  are in contact with the top metal layer  26  and so provide electrical connection between the CMOS and the heater element  10 . The sloped side faces of the first sacrificial scaffold  54  ensure good electrical connection between the heater element  10  and the electrodes  15 , since the heater material is deposited with sufficient thickness around the scaffold  54 . Any thin areas of heater material (due to insufficient side face deposition) would increase resistivity and affect heater performance. 
     Adjacent unit cells are electrically insulated from each other by virtue of grooves etched around the perimeter of each unit cell. The grooves are etched at the same time as defining the heater element  10 . 
     Referring to  FIG. 21 , in the subsequent step a second sacrificial scaffold  39  of photoresist is deposited over the heater material. The second sacrificial scaffold  39  is exposed and developed to define sidewalls for the cylindrical nozzle chamber and perimeter sidewalls for each unit cell. The second sacrificial scaffold  39  is also UV cured and hardbaked to prevent any reflow of the photoresist during subsequent high-temperature deposition of the silicon nitride roof material. 
     Referring to  FIG. 22 , silicon nitride is deposited onto the second sacrificial scaffold  39  by plasma enhanced chemical vapour deposition. The silicon nitride forms a roof  44  over each unit cell, which is the nozzle plate  2  for a row of nozzles. Chamber sidewalls  6  and unit cell sidewalls  56  are also formed by deposition of silicon nitride. 
     Referring to  FIG. 23 , the nozzle rim  4  is etched partially through the roof  44 , by placing a suitably patterned photoresist mask over the roof, etching for a controlled period of time and removing the photoresist by ashing. 
     Referring to  FIG. 24 , the nozzle aperture  5  is etched through the roof  24  down to the second sacrificial scaffold  39 . Again, the etch is performed by placing a suitably patterned photoresist mask over the roof, etching down to the scaffold  39  and removing the photoresist mask. 
     With the nozzle structure now fully formed on a frontside of the silicon substrate  21 , an ink supply channel  32  is etched from the backside of the substrate  21 , which meets with the front plug  53 . 
     Referring to  FIG. 25 , after formation of the ink supply channel  32 , the first and second sacrificial scaffolds of photoresist, together with the front plug  53  are ashed off using an O 2  plasma. Accordingly, fluid connection is made from the ink supply channel  32  through to the nozzle aperture  5 . 
     It should be noted that a portion of photoresist, on either side of the nozzle chamber sidewalls  6 , remains encapsulated by the roof  44 , the unit cell sidewalls  56  and the chamber sidewalls  6 . This portion of photoresist is sealed from the O 2  ashing plasma and, therefore, remains intact after fabrication of the printhead. This encapsulated photoresist advantageously provides additional robustness for the printhead by supporting the nozzle plate  2 . Hence, the printhead has a robust nozzle plate spanning continuously over rows of nozzles, and being supported by solid blocks of hardened photoresist, in addition to support walls. 
     Hydrophobic Coating of Front Face 
     Referring to  FIG. 24 , it can been seen that a hydrophobic material may be deposited onto the roof  44  at this stage by, for example, chemical vapour deposition. The whole of the front face of the printhead may be coated with hydrophobic material. Alternatively, predetermined regions of the roof  44  (e.g. regions surrounding each nozzle aperture  5 ) may be coated. However, referring to  FIG. 25 , the final stage of printhead fabrication involves ashing off the photoresist, which occupies the nozzle chambers. Since hydrophobic coating materials are generally organic in nature, the ashing process will remove the hydrophobic coating on the roof  44  as well as the photoresist  39  in the nozzle chambers. Hence, a hydrophobic coating step at this stage would ultimately have no effect on the hydrophobicity of the roof  44 . 
     Referring to  FIG. 25 , it can be seen that a hydrophobic material may be deposited onto the roof  44  at this stage by, for example, chemical vapour deposition. However, the CVD process will deposit the hydrophobic material both onto the roof  44 , onto nozzle chamber sidewalls, onto the heater element  10  and inside ink supply channels  32 . A hydrophobic coating inside the nozzle chambers and ink supply channels would be highly undesirable in terms of creating a positive ink pressure biased towards the nozzle chambers. A hydrophobic coating on the heater element  10  would be equally undesirable in terms of kogation during printing. 
     Referring to  FIG. 27 , there is shown a process for depositing a hydrophobic material onto the roof  44 , which eliminates the aforementioned selectivity problems. Before deposition of the hydrophobic material, the printhead is primed with a liquid, which fills the ink supply channels  32  and nozzle chamber up to the rim  4 . The liquid is preferably ink so that the hydrophobic deposition step can be incorporated into the overall printer manufacturing process. Once primed with ink  60 , the front face of the printhead, including the roof  44 , is coated with a hydrophobic material  61  by chemical vapour deposition (see  FIG. 28 ). The hydrophobic material  61  cannot be deposited inside the nozzle chamber, because the ink  60  effectively seals the nozzle aperture  5  from the vapour. Hence, the ink  60  protects the nozzle chamber and allows selective deposition of the hydrophobic material  61  onto the roof  44 . Accordingly, the final printhead has a hydrophobic front face in combination with hydrophilic nozzle chambers and ink supply channels. 
     The choice of hydrophobic material is not critical. Any hydrophobic compound, which can adhere to the roof  44  by either covalent bonding, ionic bonding, chemisorption or adsorption may be used. The choice of hydrophobic material will depend on the material forming the roof  44  and also the liquid used to prime the nozzles. 
     Typically, the roof  44  is formed from silicon nitride, silicon oxide or silicon oxynitride. In this case, the hydrophobic material is typically a compound, which can form covalent bonds with the oxygen or nitrogen atoms exposed on the surface of the roof Examples of suitable compounds are silyl chlorides (including monochlorides, dichlorides, trichlorides) having at least one hydrophobic group. The hydrophobic group is typically a C 1-20  alkyl group, optionally substituted with a plurality of fluorine atoms. The hydrophobic group may be perfluorinated, partially fluorinated or non-fluorinated. Examples of suitable hydrophobic compounds include: trimethylsilyl chloride, dimethylsilyl dichloride, methylsilyl trichloride, triethylsilyl chloride, octyldimethylsilyl chloride, perfluorooctyldimethylsilyl chloride, perfluorooctylsilyl trichloride, perfluorooctylchlorosilane etc. 
     Typically, the nozzles are primed with an inkjet ink. In this case, the hydrophobic material is typically a compound, which does not polymerise in aqueous solution and form a skin across the nozzle aperture  5 . Examples of non-polymerizable hydrophobic compounds include: trimethylsilyl chloride, triethylsilyl chloride, perfluorooctyldimethylsilyl chloride, perfluorooctylchlorosilane etc. 
     Whilst silyl chlorides have been exemplified as hydrophobizing compounds hereinabove, it will be appreciated that the present invention may be used in conjunction with any hydrophobizing compound, which can be deposited by CVD or another suitable deposition process. 
     Other Embodiments 
     The invention has been described above with reference to printheads using bubble forming heater elements. However, it is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays. 
     It will be appreciated by ordinary workers in this field that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. 
     Ink Jet Technologies 
     The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. 
     The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. In conventional thermal inkjet printheads, this leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out. 
     The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles. 
     Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include: 
     low power (less than 10 Watts) 
     high resolution capability (1,600 dpi or more) 
     photographic quality output 
     low manufacturing cost 
     small size (pagewidth times minimum cross section) 
     high speed (&lt;2 seconds per page). 
     All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications. 
     The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems. 
     For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry. 
     Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding. 
     Tables of Drop-on-Demand Ink Jets 
     Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee. 
     The following tables form the axes of an eleven dimensional table of ink jet types. 
     Actuator mechanism (18 types) 
     Basic operation mode (7 types) 
     Auxiliary mechanism (8 types) 
     Actuator amplification or modification method (17 types) 
     Actuator motion (19 types) 
     Nozzle refill method (4 types) 
     Method of restricting back-flow through inlet (10 types) 
     Nozzle clearing method (9 types) 
     Nozzle plate construction (9 types) 
     Drop ejection direction (5 types) 
     Ink type (7 types) 
     The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of inkjet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications. 
     Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology. 
     Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry. 
     Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc. 
     The information associated with the aforementioned 11 dimensional matrix are set out in the following tables. 
     
       
         
           
               
            
               
                   
               
               
                 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Thermal 
                 An electrothermal 
                 Large force 
                 High power 
                 Canon 
               
               
                 bubble 
                 heater heats the 
                 generated 
                 Ink carrier 
                 Bubblejet 1979 
               
               
                   
                 ink to above 
                 Simple 
                 limited to water 
                 Endo et al GB 
               
               
                   
                 boiling point, 
                 construction 
                 Low 
                 patent 2,007,162 
               
               
                   
                 transferring 
                 No moving 
                 efficiency 
                 Xerox heater- 
               
               
                   
                 significant heat to 
                 parts 
                 High 
                 in-pit 1990 
               
               
                   
                 the aqueous ink. A 
                 Fast operation 
                 temperatures 
                 Hawkins et al 
               
               
                   
                 bubble nucleates 
                 Small chip 
                 required 
                 U.S. Pat. No. 4,899,181 
               
               
                   
                 and quickly forms, 
                 area required for 
                 High 
                 Hewlett- 
               
               
                   
                 expelling the ink. 
                 actuator 
                 mechanical 
                 Packard TIJ 
               
               
                   
                 The efficiency of 
                   
                 stress 
                 1982 Vaught et 
               
               
                   
                 the process is low, 
                   
                 Unusual 
                 al U.S. Pat. No. 
               
               
                   
                 with typically less 
                   
                 materials 
                 4,490,728 
               
               
                   
                 than 0.05% of the 
                   
                 required 
               
               
                   
                 electrical energy 
                   
                 Large drive 
               
               
                   
                 being transformed 
                   
                 transistors 
               
               
                   
                 into kinetic energy 
                   
                 Cavitation 
               
               
                   
                 of the drop. 
                   
                 causes actuator 
               
               
                   
                   
                   
                 failure 
               
               
                   
                   
                   
                 Kogation 
               
               
                   
                   
                   
                 reduces bubble 
               
               
                   
                   
                   
                 formation 
               
               
                   
                   
                   
                 Large print 
               
               
                   
                   
                   
                 heads are 
               
               
                   
                   
                   
                 difficult to 
               
               
                   
                   
                   
                 fabricate 
               
               
                 Piezo- 
                 A piezoelectric 
                 Low power 
                 Very large 
                 Kyser et al 
               
               
                 electric 
                 crystal such as 
                 consumption 
                 area required for 
                 U.S. Pat. No. 3,946,398 
               
               
                   
                 lead lanthanum 
                 Many ink 
                 actuator 
                 Zoltan U.S. Pat. No. 
               
               
                   
                 zirconate (PZT) is 
                 types can be 
                 Difficult to 
                 3,683,212 
               
               
                   
                 electrically 
                 used 
                 integrate with 
                 1973 Stemme 
               
               
                   
                 activated, and 
                 Fast operation 
                 electronics 
                 U.S. Pat. No. 3,747,120 
               
               
                   
                 either expands, 
                 High 
                 High voltage 
                 Epson Stylus 
               
               
                   
                 shears, or bends to 
                 efficiency 
                 drive transistors 
                 Tektronix 
               
               
                   
                 apply pressure to 
                   
                 required 
                 IJ04 
               
               
                   
                 the ink, ejecting 
                   
                 Full 
               
               
                   
                 drops. 
                   
                 pagewidth print 
               
               
                   
                   
                   
                 heads 
               
               
                   
                   
                   
                 impractical due 
               
               
                   
                   
                   
                 to actuator size 
               
               
                   
                   
                   
                 Requires 
               
               
                   
                   
                   
                 electrical poling 
               
               
                   
                   
                   
                 in high field 
               
               
                   
                   
                   
                 strengths during 
               
               
                   
                   
                   
                 manufacture 
               
               
                 Electro- 
                 An electric field is 
                 Low power 
                 Low 
                 Seiko Epson, 
               
               
                 strictive 
                 used to activate 
                 consumption 
                 maximum strain 
                 Usui et all JP 
               
               
                   
                 electrostriction in 
                 Many ink 
                 (approx. 0.01%) 
                 253401/96 
               
               
                   
                 relaxor materials 
                 types can be 
                 Large area 
                 IJ04 
               
               
                   
                 such as lead 
                 used 
                 required for 
               
               
                   
                 lanthanum 
                 Low thermal 
                 actuator due to 
               
               
                   
                 zirconate titanate 
                 expansion 
                 low strain 
               
               
                   
                 (PLZT) or lead 
                 Electric field 
                 Response 
               
               
                   
                 magnesium 
                 strength required 
                 speed is 
               
               
                   
                 niobate (PMN). 
                 (approx. 3.5 V/μm) 
                 marginal (~10 μs) 
               
               
                   
                   
                 can be 
                 High voltage 
               
               
                   
                   
                 generated 
                 drive transistors 
               
               
                   
                   
                 without 
                 required 
               
               
                   
                   
                 difficulty 
                 Full 
               
               
                   
                   
                 Does not 
                 pagewidth print 
               
               
                   
                   
                 require electrical 
                 heads 
               
               
                   
                   
                 poling 
                 impractical due 
               
               
                   
                   
                   
                 to actuator size 
               
               
                 Ferro- 
                 An electric field is 
                 Low power 
                 Difficult to 
                 IJ04 
               
               
                 electric 
                 used to induce a 
                 consumption 
                 integrate with 
               
               
                   
                 phase transition 
                 Many ink 
                 electronics 
               
               
                   
                 between the 
                 types can be 
                 Unusual 
               
               
                   
                 antiferroelectric 
                 used 
                 materials such as 
               
               
                   
                 (AFE) and 
                 Fast operation 
                 PLZSnT are 
               
               
                   
                 ferroelectric (FE) 
                 (&lt;1 μs) 
                 required 
               
               
                   
                 phase. Perovskite 
                 Relatively 
                 Actuators 
               
               
                   
                 materials such as 
                 high longitudinal 
                 require a large 
               
               
                   
                 tin modified lead 
                 strain 
                 area 
               
               
                   
                 lanthanum 
                 High 
               
               
                   
                 zirconate titanate 
                 efficiency 
               
               
                   
                 (PLZSnT) exhibit 
                 Electric field 
               
               
                   
                 large strains of up 
                 strength of 
               
               
                   
                 to 1% associated 
                 around 3 V/μm 
               
               
                   
                 with the AFE to 
                 can be readily 
               
               
                   
                 FE phase 
                 provided 
               
               
                   
                 transition. 
               
               
                 Electro- 
                 Conductive plates 
                 Low power 
                 Difficult to 
                 IJ02, IJ04 
               
               
                 static 
                 are separated by a 
                 consumption 
                 operate 
               
               
                 plates 
                 compressible or 
                 Many ink 
                 electrostatic 
               
               
                   
                 fluid dielectric 
                 types can be 
                 devices in an 
               
               
                   
                 (usually air). Upon 
                 used 
                 aqueous 
               
               
                   
                 application of a 
                 Fast operation 
                 environment 
               
               
                   
                 voltage, the plates 
                   
                 The 
               
               
                   
                 attract each other 
                   
                 electrostatic 
               
               
                   
                 and displace ink, 
                   
                 actuator will 
               
               
                   
                 causing drop 
                   
                 normally need to 
               
               
                   
                 ejection. The 
                   
                 be separated 
               
               
                   
                 conductive plates 
                   
                 from the ink 
               
               
                   
                 may be in a comb 
                   
                 Very large 
               
               
                   
                 or honeycomb 
                   
                 area required to 
               
               
                   
                 structure, or 
                   
                 achieve high 
               
               
                   
                 stacked to increase 
                   
                 forces 
               
               
                   
                 the surface area 
                   
                 High voltage 
               
               
                   
                 and therefore the 
                   
                 drive transistors 
               
               
                   
                 force. 
                   
                 may be required 
               
               
                   
                   
                   
                 Full 
               
               
                   
                   
                   
                 pagewidth print 
               
               
                   
                   
                   
                 heads are not 
               
               
                   
                   
                   
                 competitive due 
               
               
                   
                   
                   
                 to actuator size 
               
               
                 Electro- 
                 A strong electric 
                 Low current 
                 High voltage 
                 1989 Saito et 
               
               
                 static pull 
                 field is applied to 
                 consumption 
                 required 
                 al, U.S. Pat. No. 
               
               
                 on ink 
                 the ink, whereupon 
                 Low 
                 May be 
                 4,799,068 
               
               
                   
                 electrostatic 
                 temperature 
                 damaged by 
                 1989 Miura et 
               
               
                   
                 attraction 
                   
                 sparks due to air 
                 al, U.S. Pat. No. 
               
               
                   
                 accelerates the ink 
                   
                 breakdown 
                 4,810,954 
               
               
                   
                 towards the print 
                   
                 Required field 
                 Tone-jet 
               
               
                   
                 medium. 
                   
                 strength 
               
               
                   
                   
                   
                 increases as the 
               
               
                   
                   
                   
                 drop size 
               
               
                   
                   
                   
                 decreases 
               
               
                   
                   
                   
                 High voltage 
               
               
                   
                   
                   
                 drive transistors 
               
               
                   
                   
                   
                 required 
               
               
                   
                   
                   
                 Electrostatic 
               
               
                   
                   
                   
                 field attracts dust 
               
               
                 Permanent 
                 An electromagnet 
                 Low power 
                 Complex 
                 IJ07, IJ10 
               
               
                 magnet 
                 directly attracts a 
                 consumption 
                 fabrication 
               
               
                 electro- 
                 permanent magnet, 
                 Many ink 
                 Permanent 
               
               
                 magnetic 
                 displacing ink and 
                 types can be 
                 magnetic 
               
               
                   
                 causing drop 
                 used 
                 material such as 
               
               
                   
                 ejection. Rare 
                 Fast operation 
                 Neodymium Iron 
               
               
                   
                 earth magnets with 
                 High 
                 Boron (NdFeB) 
               
               
                   
                 a field strength 
                 efficiency 
                 required. 
               
               
                   
                 around 1 Tesla can 
                 Easy 
                 High local 
               
               
                   
                 be used. Examples 
                 extension from 
                 currents required 
               
               
                   
                 are: Samarium 
                 single nozzles to 
                 Copper 
               
               
                   
                 Cobalt (SaCo) and 
                 pagewidth print 
                 metalization 
               
               
                   
                 magnetic materials 
                 heads 
                 should be used 
               
               
                   
                 in the neodymium 
                   
                 for long 
               
               
                   
                 iron boron family 
                   
                 electromigration 
               
               
                   
                 (NdFeB, 
                   
                 lifetime and low 
               
               
                   
                 NdDyFeBNb, 
                   
                 resistivity 
               
               
                   
                 NdDyFeB, etc) 
                   
                 Pigmented 
               
               
                   
                   
                   
                 inks are usually 
               
               
                   
                   
                   
                 infeasible 
               
               
                   
                   
                   
                 Operating 
               
               
                   
                   
                   
                 temperature 
               
               
                   
                   
                   
                 limited to the 
               
               
                   
                   
                   
                 Curie 
               
               
                   
                   
                   
                 temperature 
               
               
                   
                   
                   
                 (around 540 K) 
               
               
                 Soft 
                 A solenoid 
                 Low power 
                 Complex 
                 IJ01, IJ05, 
               
               
                 magnetic 
                 induced a 
                 consumption 
                 fabrication 
                 IJ08, IJ10, IJ12, 
               
               
                 core 
                 magnetic field in a 
                 Many ink 
                 Materials not 
                 IJ14, IJ15, IJ17 
               
               
                 electro- 
                 soft magnetic core 
                 types can be 
                 usually present 
               
               
                 magnetic 
                 or yoke fabricated 
                 used 
                 in a CMOS fab 
               
               
                   
                 from a ferrous 
                 Fast operation 
                 such as NiFe, 
               
               
                   
                 material such as 
                 High 
                 CoNiFe, or CoFe 
               
               
                   
                 electroplated iron 
                 efficiency 
                 are required 
               
               
                   
                 alloys such as 
                 Easy 
                 High local 
               
               
                   
                 CoNiFe [1], CoFe, 
                 extension from 
                 currents required 
               
               
                   
                 or NiFe alloys. 
                 single nozzles to 
                 Copper 
               
               
                   
                 Typically, the soft 
                 pagewidth print 
                 metalization 
               
               
                   
                 magnetic material 
                 heads 
                 should be used 
               
               
                   
                 is in two parts, 
                   
                 for long 
               
               
                   
                 which are 
                   
                 electromigration 
               
               
                   
                 normally held 
                   
                 lifetime and low 
               
               
                   
                 apart by a spring. 
                   
                 resistivity 
               
               
                   
                 When the solenoid 
                   
                 Electroplating 
               
               
                   
                 is actuated, the two 
                   
                 is required 
               
               
                   
                 parts attract, 
                   
                 High 
               
               
                   
                 displacing the ink. 
                   
                 saturation flux 
               
               
                   
                   
                   
                 density is 
               
               
                   
                   
                   
                 required (2.0-2.1 
               
               
                   
                   
                   
                 T is achievable 
               
               
                   
                   
                   
                 with CoNiFe 
               
               
                   
                   
                   
                 [1]) 
               
               
                 Lorenz 
                 The Lorenz force 
                 Low power 
                 Force acts as a 
                 IJ06, IJ11, 
               
               
                 force 
                 acting on a current 
                 consumption 
                 twisting motion 
                 IJ13, IJ16 
               
               
                   
                 carrying wire in a 
                 Many ink 
                 Typically, 
               
               
                   
                 magnetic field is 
                 types can be 
                 only a quarter of 
               
               
                   
                 utilized. 
                 used 
                 the solenoid 
               
               
                   
                 This allows the 
                 Fast operation 
                 length provides 
               
               
                   
                 magnetic field to 
                 High 
                 force in a useful 
               
               
                   
                 be supplied 
                 efficiency 
                 direction 
               
               
                   
                 externally to the 
                 Easy 
                 High local 
               
               
                   
                 print head, for 
                 extension from 
                 currents required 
               
               
                   
                 example with rare 
                 single nozzles to 
                 Copper 
               
               
                   
                 earth permanent 
                 pagewidth print 
                 metalization 
               
               
                   
                 magnets. 
                 heads 
                 should be used 
               
               
                   
                 Only the current 
                   
                 for long 
               
               
                   
                 carrying wire need 
                   
                 electromigration 
               
               
                   
                 be fabricated on 
                   
                 lifetime and low 
               
               
                   
                 the print-head, 
                   
                 resistivity 
               
               
                   
                 simplifying 
                   
                 Pigmented 
               
               
                   
                 materials 
                   
                 inks are usually 
               
               
                   
                 requirements. 
                   
                 infeasible 
               
               
                 Magneto- 
                 The actuator uses 
                 Many ink 
                 Force acts as a 
                 Fischenbeck, 
               
               
                 striction 
                 the giant 
                 types can be 
                 twisting motion 
                 U.S. Pat. No. 4,032,929 
               
               
                   
                 magnetostrictive 
                 used 
                 Unusual 
                 IJ25 
               
               
                   
                 effect of materials 
                 Fast operation 
                 materials such as 
               
               
                   
                 such as Terfenol-D 
                 Easy 
                 Terfenol-D are 
               
               
                   
                 (an alloy of 
                 extension from 
                 required 
               
               
                   
                 terbium, 
                 single nozzles to 
                 High local 
               
               
                   
                 dysprosium and 
                 pagewidth print 
                 currents required 
               
               
                   
                 iron developed at 
                 heads 
                 Copper 
               
               
                   
                 the Naval 
                 High force is 
                 metalization 
               
               
                   
                 Ordnance 
                 available 
                 should be used 
               
               
                   
                 Laboratory, hence 
                   
                 for long 
               
               
                   
                 Ter-Fe-NOL). For 
                   
                 electromigration 
               
               
                   
                 best efficiency, the 
                   
                 lifetime and low 
               
               
                   
                 actuator should be 
                   
                 resistivity 
               
               
                   
                 pre-stressed to 
                   
                 Pre-stressing 
               
               
                   
                 approx. 8 MPa. 
                   
                 may be required 
               
               
                 Surface 
                 Ink under positive 
                 Low power 
                 Requires 
                 Silverbrook, 
               
               
                 tension 
                 pressure is held in 
                 consumption 
                 supplementary 
                 EP 0771 658 A2 
               
               
                 reduction 
                 a nozzle by surface 
                 Simple 
                 force to effect 
                 and related 
               
               
                   
                 tension. The 
                 construction 
                 drop separation 
                 patent 
               
               
                   
                 surface tension of 
                 No unusual 
                 Requires 
                 applications 
               
               
                   
                 the ink is reduced 
                 materials 
                 special ink 
               
               
                   
                 below the bubble 
                 required in 
                 surfactants 
               
               
                   
                 threshold, causing 
                 fabrication 
                 Speed may be 
               
               
                   
                 the ink to egress 
                 High 
                 limited by 
               
               
                   
                 from the nozzle. 
                 efficiency 
                 surfactant 
               
               
                   
                   
                 Easy 
                 properties 
               
               
                   
                   
                 extension from 
               
               
                   
                   
                 single nozzles to 
               
               
                   
                   
                 pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 Viscosity 
                 The ink viscosity 
                 Simple 
                 Requires 
                 Silverbrook, 
               
               
                 reduction 
                 is locally reduced 
                 construction 
                 supplementary 
                 EP 0771 658 A2 
               
               
                   
                 to select which 
                 No unusual 
                 force to effect 
                 and related 
               
               
                   
                 drops are to be 
                 materials 
                 drop separation 
                 patent 
               
               
                   
                 ejected. A 
                 required in 
                 Requires 
                 applications 
               
               
                   
                 viscosity reduction 
                 fabrication 
                 special ink 
               
               
                   
                 can be achieved 
                 Easy 
                 viscosity 
               
               
                   
                 electrothermally 
                 extension from 
                 properties 
               
               
                   
                 with most inks, but 
                 single nozzles to 
                 High speed is 
               
               
                   
                 special inks can be 
                 pagewidth print 
                 difficult to 
               
               
                   
                 engineered for a 
                 heads 
                 achieve 
               
               
                   
                 100:1 viscosity 
                   
                 Requires 
               
               
                   
                 reduction. 
                   
                 oscillating ink 
               
               
                   
                   
                   
                 pressure 
               
               
                   
                   
                   
                 A high 
               
               
                   
                   
                   
                 temperature 
               
               
                   
                   
                   
                 difference 
               
               
                   
                   
                   
                 (typically 80 
               
               
                   
                   
                   
                 degrees) is 
               
               
                   
                   
                   
                 required 
               
               
                 Acoustic 
                 An acoustic wave 
                 Can operate 
                 Complex 
                 1993 
               
               
                   
                 is generated and 
                 without a nozzle 
                 drive circuitry 
                 Hadimioglu et 
               
               
                   
                 focussed upon the 
                 plate 
                 Complex 
                 al, EUP 550,192 
               
               
                   
                 drop ejection 
                   
                 fabrication 
                 1993 Elrod et 
               
               
                   
                 region. 
                   
                 Low 
                 al, EUP 572,220 
               
               
                   
                   
                   
                 efficiency 
               
               
                   
                   
                   
                 Poor control 
               
               
                   
                   
                   
                 of drop position 
               
               
                   
                   
                   
                 Poor control 
               
               
                   
                   
                   
                 of drop volume 
               
               
                 Thermo- 
                 An actuator which 
                 Low power 
                 Efficient 
                 IJ03, IJ09, 
               
               
                 elastic 
                 relies upon 
                 consumption 
                 aqueous 
                 IJ17, IJ18, IJ19, 
               
               
                 bend 
                 differential 
                 Many ink 
                 operation 
                 IJ20, IJ21, IJ22, 
               
               
                 actuator 
                 thermal expansion 
                 types can be 
                 requires a 
                 IJ23, IJ24, IJ27, 
               
               
                   
                 upon Joule heating 
                 used 
                 thermal insulator 
                 IJ28, IJ29, IJ30, 
               
               
                   
                 is used. 
                 Simple planar 
                 on the hot side 
                 IJ31, IJ32, IJ33, 
               
               
                   
                   
                 fabrication 
                 Corrosion 
                 IJ34, IJ35, IJ36, 
               
               
                   
                   
                 Small chip 
                 prevention can 
                 IJ37, IJ38, IJ39, 
               
               
                   
                   
                 area required for 
                 be difficult 
                 IJ40, IJ41 
               
               
                   
                   
                 each actuator 
                 Pigmented 
               
               
                   
                   
                 Fast operation 
                 inks may be 
               
               
                   
                   
                 High 
                 infeasible, as 
               
               
                   
                   
                 efficiency 
                 pigment particles 
               
               
                   
                   
                 CMOS 
                 may jam the 
               
               
                   
                   
                 compatible 
                 bend actuator 
               
               
                   
                   
                 voltages and 
               
               
                   
                   
                 currents 
               
               
                   
                   
                 Standard 
               
               
                   
                   
                 MEMS 
               
               
                   
                   
                 processes can be 
               
               
                   
                   
                 used 
               
               
                   
                   
                 Easy 
               
               
                   
                   
                 extension from 
               
               
                   
                   
                 single nozzles to 
               
               
                   
                   
                 pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 High CTE 
                 A material with a 
                 High force 
                 Requires 
                 IJ09, IJ17, 
               
               
                 thermo- 
                 very high 
                 can be generated 
                 special material 
                 IJ18, IJ20, IJ21, 
               
               
                 elastic 
                 coefficient of 
                 Three 
                 (e.g. PTFE) 
                 IJ22, IJ23, IJ24, 
               
               
                 actuator 
                 thermal expansion 
                 methods of 
                 Requires a 
                 IJ27, IJ28, IJ29, 
               
               
                   
                 (CTE) such as 
                 PTFE deposition 
                 PTFE deposition 
                 IJ30, IJ31, IJ42, 
               
               
                   
                 polytetrafluoroethylene 
                 are under 
                 process, which is 
                 IJ43, IJ44 
               
               
                   
                 (PTFE) is 
                 development: 
                 not yet standard 
               
               
                   
                 used. As high CTE 
                 chemical vapor 
                 in ULSI fabs 
               
               
                   
                 materials are 
                 deposition 
                 PTFE 
               
               
                   
                 usually non- 
                 (CVD), spin 
                 deposition 
               
               
                   
                 conductive, a 
                 coating, and 
                 cannot be 
               
               
                   
                 heater fabricated 
                 evaporation 
                 followed with 
               
               
                   
                 from a conductive 
                 PTFE is a 
                 high temperature 
               
               
                   
                 material is 
                 candidate for 
                 (above 350° C.) 
               
               
                   
                 incorporated. A 50 μm 
                 low dielectric 
                 processing 
               
               
                   
                 long PTFE 
                 constant 
                 Pigmented 
               
               
                   
                 bend actuator with 
                 insulation in 
                 inks may be 
               
               
                   
                 polysilicon heater 
                 ULSI 
                 infeasible, as 
               
               
                   
                 and 15 mW power 
                 Very low 
                 pigment particles 
               
               
                   
                 input can provide 
                 power 
                 may jam the 
               
               
                   
                 180 μN force and 
                 consumption 
                 bend actuator 
               
               
                   
                 10 μm deflection. 
                 Many ink 
               
               
                   
                 Actuator motions 
                 types can be 
               
               
                   
                 include: 
                 used 
               
               
                   
                 Bend 
                 Simple planar 
               
               
                   
                 Push 
                 fabrication 
               
               
                   
                 Buckle 
                 Small chip 
               
               
                   
                 Rotate 
                 area required for 
               
               
                   
                   
                 each actuator 
               
               
                   
                   
                 Fast operation 
               
               
                   
                   
                 High 
               
               
                   
                   
                 efficiency 
               
               
                   
                   
                 CMOS 
               
               
                   
                   
                 compatible 
               
               
                   
                   
                 voltages and 
               
               
                   
                   
                 currents 
               
               
                   
                   
                 Easy 
               
               
                   
                   
                 extension from 
               
               
                   
                   
                 single nozzles to 
               
               
                   
                   
                 pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 Conductive 
                 A polymer with a 
                 High force 
                 Requires 
                 IJ24 
               
               
                 polymer 
                 high coefficient of 
                 can be generated 
                 special materials 
               
               
                 thermo- 
                 thermal expansion 
                 Very low 
                 development 
               
               
                 elastic 
                 (such as PTFE) is 
                 power 
                 (High CTE 
               
               
                 actuator 
                 doped with 
                 consumption 
                 conductive 
               
               
                   
                 conducting 
                 Many ink 
                 polymer) 
               
               
                   
                 substances to 
                 types can be 
                 Requires a 
               
               
                   
                 increase its 
                 used 
                 PTFE deposition 
               
               
                   
                 conductivity to 
                 Simple planar 
                 process, which is 
               
               
                   
                 about 3 orders of 
                 fabrication 
                 not yet standard 
               
               
                   
                 magnitude below 
                 Small chip 
                 in ULSI fabs 
               
               
                   
                 that of copper. The 
                 area required for 
                 PTFE 
               
               
                   
                 conducting 
                 each actuator 
                 deposition 
               
               
                   
                 polymer expands 
                 Fast operation 
                 cannot be 
               
               
                   
                 when resistively 
                 High 
                 followed with 
               
               
                   
                 heated. 
                 efficiency 
                 high temperature 
               
               
                   
                 Examples of 
                 CMOS 
                 (above 350° C.) 
               
               
                   
                 conducting 
                 compatible 
                 processing 
               
               
                   
                 dopants include: 
                 voltages and 
                 Evaporation 
               
               
                   
                 Carbon nanotubes 
                 currents 
                 and CVD 
               
               
                   
                 Metal fibers 
                 Easy 
                 deposition 
               
               
                   
                 Conductive 
                 extension from 
                 techniques 
               
               
                   
                 polymers such as 
                 single nozzles to 
                 cannot be used 
               
               
                   
                 doped 
                 pagewidth print 
                 Pigmented 
               
               
                   
                 polythiophene 
                 heads 
                 inks may be 
               
               
                   
                 Carbon granules 
                   
                 infeasible, as 
               
               
                   
                   
                   
                 pigment particles 
               
               
                   
                   
                   
                 may jam the 
               
               
                   
                   
                   
                 bend actuator 
               
               
                 Shape 
                 A shape memory 
                 High force is 
                 Fatigue limits 
                 IJ26 
               
               
                 memory 
                 alloy such as TiNi 
                 available 
                 maximum 
               
               
                 alloy 
                 (also known as 
                 (stresses of 
                 number of cycles 
               
               
                   
                 Nitinol - Nickel 
                 hundreds of 
                 Low strain 
               
               
                   
                 Titanium alloy 
                 MPa) 
                 (1%) is required 
               
               
                   
                 developed at the 
                 Large strain is 
                 to extend fatigue 
               
               
                   
                 Naval Ordnance 
                 available (more 
                 resistance 
               
               
                   
                 Laboratory) is 
                 than 3%) 
                 Cycle rate 
               
               
                   
                 thermally switched 
                 High 
                 limited by heat 
               
               
                   
                 between its weak 
                 corrosion 
                 removal 
               
               
                   
                 martensitic state 
                 resistance 
                 Requires 
               
               
                   
                 and its high 
                 Simple 
                 unusual 
               
               
                   
                 stiffness austenic 
                 construction 
                 materials (TiNi) 
               
               
                   
                 state. The shape of 
                 Easy 
                 The latent 
               
               
                   
                 the actuator in its 
                 extension from 
                 heat of 
               
               
                   
                 martensitic state is 
                 single nozzles to 
                 transformation 
               
               
                   
                 deformed relative 
                 pagewidth print 
                 must be 
               
               
                   
                 to the austenic 
                 heads 
                 provided 
               
               
                   
                 shape. The shape 
                 Low voltage 
                 High current 
               
               
                   
                 change causes 
                 operation 
                 operation 
               
               
                   
                 ejection of a drop. 
                   
                 Requires pre- 
               
               
                   
                   
                   
                 stressing to 
               
               
                   
                   
                   
                 distort the 
               
               
                   
                   
                   
                 martensitic state 
               
               
                 Linear 
                 Linear magnetic 
                 Linear 
                 Requires 
                 IJ12 
               
               
                 Magnetic 
                 actuators include 
                 Magnetic 
                 unusual 
               
               
                 Actuator 
                 the Linear 
                 actuators can be 
                 semiconductor 
               
               
                   
                 Induction Actuator 
                 constructed with 
                 materials such as 
               
               
                   
                 (LIA), Linear 
                 high thrust, long 
                 soft magnetic 
               
               
                   
                 Permanent Magnet 
                 travel, and high 
                 alloys (e.g. 
               
               
                   
                 Synchronous 
                 efficiency using 
                 CoNiFe) 
               
               
                   
                 Actuator 
                 planar 
                 Some varieties 
               
               
                   
                 (LPMSA), Linear 
                 semiconductor 
                 also require 
               
               
                   
                 Reluctance 
                 fabrication 
                 permanent 
               
               
                   
                 Synchronous 
                 techniques 
                 magnetic 
               
               
                   
                 Actuator (LRSA), 
                 Long actuator 
                 materials such as 
               
               
                   
                 Linear Switched 
                 travel is 
                 Neodymium iron 
               
               
                   
                 Reluctance 
                 available 
                 boron (NdFeB) 
               
               
                   
                 Actuator (LSRA), 
                 Medium force 
                 Requires 
               
               
                   
                 and the Linear 
                 is available 
                 complex multi- 
               
               
                   
                 Stepper Actuator 
                 Low voltage 
                 phase drive 
               
               
                   
                 (LSA). 
                 operation 
                 circuitry 
               
               
                   
                   
                   
                 High current 
               
               
                   
                   
                   
                 operation 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 BASIC OPERATION MODE 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Actuator 
                 This is the 
                 Simple 
                 Drop 
                 Thermal ink 
               
               
                 directly 
                 simplest mode of 
                 operation 
                 repetition rate is 
                 jet 
               
               
                 pushes 
                 operation: the 
                 No external 
                 usually limited 
                 Piezoelectric 
               
               
                 ink 
                 actuator directly 
                 fields required 
                 to around 10 kHz. 
                 ink jet 
               
               
                   
                 supplies sufficient 
                 Satellite drops 
                 However, 
                 IJ01, IJ02, 
               
               
                   
                 kinetic energy to 
                 can be avoided if 
                 this is not 
                 IJ03, IJ04, IJ05, 
               
               
                   
                 expel the drop. 
                 drop velocity is 
                 fundamental to 
                 IJ06, IJ07, IJ09, 
               
               
                   
                 The drop must 
                 less than 4 m/s 
                 the method, but 
                 IJ11, IJ12, IJ14, 
               
               
                   
                 have a sufficient 
                 Can be 
                 is related to the 
                 IJ16, IJ20, IJ22, 
               
               
                   
                 velocity to 
                 efficient, 
                 refill method 
                 IJ23, IJ24, IJ25, 
               
               
                   
                 overcome the 
                 depending upon 
                 normally used 
                 IJ26, IJ27, IJ28, 
               
               
                   
                 surface tension. 
                 the actuator used 
                 All of the drop 
                 IJ29, IJ30, IJ31, 
               
               
                   
                   
                   
                 kinetic energy 
                 IJ32, IJ33, IJ34, 
               
               
                   
                   
                   
                 must be 
                 IJ35, IJ36, IJ37, 
               
               
                   
                   
                   
                 provided by the 
                 IJ38, IJ39, IJ40, 
               
               
                   
                   
                   
                 actuator 
                 IJ41, IJ42, IJ43, 
               
               
                   
                   
                   
                 Satellite drops 
                 IJ44 
               
               
                   
                   
                   
                 usually form if 
               
               
                   
                   
                   
                 drop velocity is 
               
               
                   
                   
                   
                 greater than 4.5 m/s 
               
               
                 Proximity 
                 The drops to be 
                 Very simple 
                 Requires close 
                 Silverbrook, 
               
               
                   
                 printed are 
                 print head 
                 proximity 
                 EP 0771 658 A2 
               
               
                   
                 selected by some 
                 fabrication can 
                 between the 
                 and related 
               
               
                   
                 manner (e.g. 
                 be used 
                 print head and 
                 patent 
               
               
                   
                 thermally induced 
                 The drop 
                 the print media 
                 applications 
               
               
                   
                 surface tension 
                 selection means 
                 or transfer roller 
               
               
                   
                 reduction of 
                 does not need to 
                 May require 
               
               
                   
                 pressurized ink). 
                 provide the 
                 two print heads 
               
               
                   
                 Selected drops are 
                 energy required 
                 printing alternate 
               
               
                   
                 separated from the 
                 to separate the 
                 rows of the 
               
               
                   
                 ink in the nozzle 
                 drop from the 
                 image 
               
               
                   
                 by contact with the 
                 nozzle 
                 Monolithic 
               
               
                   
                 print medium or a 
                   
                 color print heads 
               
               
                   
                 transfer roller. 
                   
                 are difficult 
               
               
                 Electro- 
                 The drops to be 
                 Very simple 
                 Requires very 
                 Silverbrook, 
               
               
                 static pull 
                 printed are 
                 print head 
                 high electrostatic 
                 EP 0771 658 A2 
               
               
                 on ink 
                 selected by some 
                 fabrication can 
                 field 
                 and related 
               
               
                   
                 manner (e.g. 
                 be used 
                 Electrostatic 
                 patent 
               
               
                   
                 thermally induced 
                 The drop 
                 field for small 
                 applications 
               
               
                   
                 surface tension 
                 selection means 
                 nozzle sizes is 
                 Tone-Jet 
               
               
                   
                 reduction of 
                 does not need to 
                 above air 
               
               
                   
                 pressurized ink). 
                 provide the 
                 breakdown 
               
               
                   
                 Selected drops are 
                 energy required 
                 Electrostatic 
               
               
                   
                 separated from the 
                 to separate the 
                 field may attract 
               
               
                   
                 ink in the nozzle 
                 drop from the 
                 dust 
               
               
                   
                 by a strong electric 
                 nozzle 
               
               
                   
                 field. 
               
               
                 Magnetic 
                 The drops to be 
                 Very simple 
                 Requires 
                 Silverbrook, 
               
               
                 pull on 
                 printed are 
                 print head 
                 magnetic ink 
                 EP 0771 658 A2 
               
               
                 ink 
                 selected by some 
                 fabrication can 
                 Ink colors 
                 and related 
               
               
                   
                 manner (e.g. 
                 be used 
                 other than black 
                 patent 
               
               
                   
                 thermally induced 
                 The drop 
                 are difficult 
                 applications 
               
               
                   
                 surface tension 
                 selection means 
                 Requires very 
               
               
                   
                 reduction of 
                 does not need to 
                 high magnetic 
               
               
                   
                 pressurized ink). 
                 provide the 
                 fields 
               
               
                   
                 Selected drops are 
                 energy required 
               
               
                   
                 separated from the 
                 to separate the 
               
               
                   
                 ink in the nozzle 
                 drop from the 
               
               
                   
                 by a strong 
                 nozzle 
               
               
                   
                 magnetic field 
               
               
                   
                 acting on the 
               
               
                   
                 magnetic ink. 
               
               
                 Shutter 
                 The actuator 
                 High speed 
                 Moving parts 
                 IJ13, IJ17, 
               
               
                   
                 moves a shutter to 
                 (&gt;50 kHz) 
                 are required 
                 IJ21 
               
               
                   
                 block ink flow to 
                 operation can be 
                 Requires ink 
               
               
                   
                 the nozzle. The ink 
                 achieved due to 
                 pressure 
               
               
                   
                 pressure is pulsed 
                 reduced refill 
                 modulator 
               
               
                   
                 at a multiple of the 
                 time 
                 Friction and 
               
               
                   
                 drop ejection 
                 Drop timing 
                 wear must be 
               
               
                   
                 frequency. 
                 can be very 
                 considered 
               
               
                   
                   
                 accurate 
                 Stiction is 
               
               
                   
                   
                 The actuator 
                 possible 
               
               
                   
                   
                 energy can be 
               
               
                   
                   
                 very low 
               
               
                 Shuttered 
                 The actuator 
                 Actuators with 
                 Moving parts 
                 IJ08, IJ15, 
               
               
                 grill 
                 moves a shutter to 
                 small travel can 
                 are required 
                 IJ18, IJ19 
               
               
                   
                 block ink flow 
                 be used 
                 Requires ink 
               
               
                   
                 through a grill to 
                 Actuators with 
                 pressure 
               
               
                   
                 the nozzle. The 
                 small force can 
                 modulator 
               
               
                   
                 shutter movement 
                 be used 
                 Friction and 
               
               
                   
                 need only be equal 
                 High speed 
                 wear must be 
               
               
                   
                 to the width of the 
                 (&gt;50 kHz) 
                 considered 
               
               
                   
                 grill holes. 
                 operation can be 
                 Stiction is 
               
               
                   
                   
                 achieved 
                 possible 
               
               
                 Pulsed 
                 A pulsed magnetic 
                 Extremely low 
                 Requires an 
                 IJ10 
               
               
                 magnetic 
                 field attracts an 
                 energy operation 
                 external pulsed 
               
               
                 pull on 
                 ‘ink pusher’ at the 
                 is possible 
                 magnetic field 
               
               
                 ink 
                 drop ejection 
                 No heat 
                 Requires 
               
               
                 pusher 
                 frequency. An 
                 dissipation 
                 special materials 
               
               
                   
                 actuator controls a 
                 problems 
                 for both the 
               
               
                   
                 catch, which 
                   
                 actuator and the 
               
               
                   
                 prevents the ink 
                   
                 ink pusher 
               
               
                   
                 pusher from 
                   
                 Complex 
               
               
                   
                 moving when a 
                   
                 construction 
               
               
                   
                 drop is not to be 
               
               
                   
                 ejected. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 The actuator 
                 Simplicity of 
                 Drop ejection 
                 Most ink jets, 
               
               
                   
                 directly fires the 
                 construction 
                 energy must be 
                 including 
               
               
                   
                 ink drop, and there 
                 Simplicity of 
                 supplied by 
                 piezoelectric and 
               
               
                   
                 is no external field 
                 operation 
                 individual nozzle 
                 thermal bubble. 
               
               
                   
                 or other 
                 Small physical 
                 actuator 
                 IJ01, IJ02, 
               
               
                   
                 mechanism 
                 size 
                   
                 IJ03, IJ04, IJ05, 
               
               
                   
                 required. 
                   
                   
                 IJ07, IJ09, IJ11, 
               
               
                   
                   
                   
                   
                 IJ12, IJ14, IJ20, 
               
               
                   
                   
                   
                   
                 IJ22, IJ23, IJ24, 
               
               
                   
                   
                   
                   
                 IJ25, IJ26, IJ27, 
               
               
                   
                   
                   
                   
                 IJ28, IJ29, IJ30, 
               
               
                   
                   
                   
                   
                 IJ31, IJ32, IJ33, 
               
               
                   
                   
                   
                   
                 IJ34, IJ35, IJ36, 
               
               
                   
                   
                   
                   
                 IJ37, IJ38, IJ39, 
               
               
                   
                   
                   
                   
                 IJ40, IJ41, IJ42, 
               
               
                   
                   
                   
                   
                 IJ43, IJ44 
               
               
                 Oscillating 
                 The ink pressure 
                 Oscillating ink 
                 Requires 
                 Silverbrook, 
               
               
                 ink 
                 oscillates, 
                 pressure can 
                 external ink 
                 EP 0771 658 A2 
               
               
                 pressure 
                 providing much of 
                 provide a refill 
                 pressure 
                 and related 
               
               
                 (including 
                 the drop ejection 
                 pulse, allowing 
                 oscillator 
                 patent 
               
               
                 acoustic 
                 energy. The 
                 higher operating 
                 Ink pressure 
                 applications 
               
               
                 stimulation) 
                 actuator selects 
                 speed 
                 phase and 
                 IJ08, IJ13, 
               
               
                   
                 which drops are to 
                 The actuators 
                 amplitude must 
                 IJ15, IJ17, IJ18, 
               
               
                   
                 be fired by 
                 may operate 
                 be carefully 
                 IJ19, IJ21 
               
               
                   
                 selectively 
                 with much lower 
                 controlled 
               
               
                   
                 blocking or 
                 energy 
                 Acoustic 
               
               
                   
                 enabling nozzles. 
                 Acoustic 
                 reflections in the 
               
               
                   
                 The ink pressure 
                 lenses can be 
                 ink chamber 
               
               
                   
                 oscillation may be 
                 used to focus the 
                 must be 
               
               
                   
                 achieved by 
                 sound on the 
                 designed for 
               
               
                   
                 vibrating the print 
                 nozzles 
               
               
                   
                 head, or preferably 
               
               
                   
                 by an actuator in 
               
               
                   
                 the ink supply. 
               
               
                 Media 
                 The print head is 
                 Low power 
                 Precision 
                 Silverbrook, 
               
               
                 proximity 
                 placed in close 
                 High accuracy 
                 assembly 
                 EP 0771 658 A2 
               
               
                   
                 proximity to the 
                 Simple print 
                 required 
                 and related 
               
               
                   
                 print medium. 
                 head 
                 Paper fibers 
                 patent 
               
               
                   
                 Selected drops 
                 construction 
                 may cause 
                 applications 
               
               
                   
                 protrude from the 
                   
                 problems 
               
               
                   
                 print head further 
                   
                 Cannot print 
               
               
                   
                 than unselected 
                   
                 on rough 
               
               
                   
                 drops, and contact 
                   
                 substrates 
               
               
                   
                 the print medium. 
               
               
                   
                 The drop soaks 
               
               
                   
                 into the medium 
               
               
                   
                 fast enough to 
               
               
                   
                 cause drop 
               
               
                   
                 separation. 
               
               
                 Transfer 
                 Drops are printed 
                 High accuracy 
                 Bulky 
                 Silverbrook, 
               
               
                 roller 
                 to a transfer roller 
                 Wide range of 
                 Expensive 
                 EP 0771 658 A2 
               
               
                   
                 instead of straight 
                 print substrates 
                 Complex 
                 and related 
               
               
                   
                 to the print 
                 can be used 
                 construction 
                 patent 
               
               
                   
                 medium. A 
                 Ink can be 
                   
                 applications 
               
               
                   
                 transfer roller can 
                 dried on the 
                   
                 Tektronix hot 
               
               
                   
                 also be used for 
                 transfer roller 
                   
                 melt 
               
               
                   
                 proximity drop 
                   
                   
                 piezoelectric ink 
               
               
                   
                 separation. 
                   
                   
                 jet 
               
               
                   
                   
                   
                   
                 Any of the IJ 
               
               
                   
                   
                   
                   
                 series 
               
               
                 Electro- 
                 An electric field is 
                 Low power 
                 Field strength 
                 Silverbrook, 
               
               
                 static 
                 used to accelerate 
                 Simple print 
                 required for 
                 EP 0771 658 A2 
               
               
                   
                 selected drops 
                 head 
                 separation of 
                 and related 
               
               
                   
                 towards the print 
                 construction 
                 small drops is 
                 patent 
               
               
                   
                 medium. 
                   
                 near or above air 
                 applications 
               
               
                   
                   
                   
                 breakdown 
                 Tone-Jet 
               
               
                 Direct 
                 A magnetic field is 
                 Low power 
                 Requires 
                 Silverbrook, 
               
               
                 magnetic 
                 used to accelerate 
                 Simple print 
                 magnetic ink 
                 EP 0771 658 A2 
               
               
                 field 
                 selected drops of 
                 head 
                 Requires 
                 and related 
               
               
                   
                 magnetic ink 
                 construction 
                 strong magnetic 
                 patent 
               
               
                   
                 towards the print 
                   
                 field 
                 applications 
               
               
                   
                 medium. 
               
               
                 Cross 
                 The print head is 
                 Does not 
                 Requires 
                 IJ06, IJ16 
               
               
                 magnetic 
                 placed in a 
                 require magnetic 
                 external magnet 
               
               
                 field 
                 constant magnetic 
                 materials to be 
                 Current 
               
               
                   
                 field. The Lorenz 
                 integrated in the 
                 densities may be 
               
               
                   
                 force in a current 
                 print head 
                 high, resulting in 
               
               
                   
                 carrying wire is 
                 manufacturing 
                 electromigration 
               
               
                   
                 used to move the 
                 process 
                 problems 
               
               
                   
                 actuator. 
               
               
                 Pulsed 
                 A pulsed magnetic 
                 Very low 
                 Complex print 
                 IJ10 
               
               
                 magnetic 
                 field is used to 
                 power operation 
                 head 
               
               
                 field 
                 cyclically attract a 
                 is possible 
                 construction 
               
               
                   
                 paddle, which 
                 Small print 
                 Magnetic 
               
               
                   
                 pushes on the ink. 
                 head size 
                 materials 
               
               
                   
                 A small actuator 
                   
                 required in print 
               
               
                   
                 moves a catch, 
                   
                 head 
               
               
                   
                 which selectively 
               
               
                   
                 prevents the 
               
               
                   
                 paddle from 
               
               
                   
                 moving. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 ACTUATOR AMPLIFICATION OR MODIFICATION METHOD 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 No actuator 
                 Operational 
                 Many actuator 
                 Thermal 
               
               
                   
                 mechanical 
                 simplicity 
                 mechanisms 
                 Bubble Ink jet 
               
               
                   
                 amplification is 
                   
                 have insufficient 
                 IJ01, IJ02, 
               
               
                   
                 used. The actuator 
                   
                 travel, or 
                 IJ06, IJ07, IJ16, 
               
               
                   
                 directly drives the 
                   
                 insufficient 
                 IJ25, IJ26 
               
               
                   
                 drop ejection 
                   
                 force, to 
               
               
                   
                 process. 
                   
                 efficiently drive 
               
               
                   
                   
                   
                 the drop ejection 
               
               
                   
                   
                   
                 process 
               
               
                 Differential 
                 An actuator 
                 Provides 
                 High stresses 
                 Piezoelectric 
               
               
                 expansion 
                 material expands 
                 greater travel in 
                 are involved 
                 IJ03, IJ09, 
               
               
                 bend 
                 more on one side 
                 a reduced print 
                 Care must be 
                 IJ17, IJ18, IJ19, 
               
               
                 actuator 
                 than on the other. 
                 head area 
                 taken that the 
                 IJ20, IJ21, IJ22, 
               
               
                   
                 The expansion 
                   
                 materials do not 
                 IJ23, IJ24, IJ27, 
               
               
                   
                 may be thermal, 
                   
                 delaminate 
                 IJ29, IJ30, IJ31, 
               
               
                   
                 piezoelectric, 
                   
                 Residual bend 
                 IJ32, IJ33, IJ34, 
               
               
                   
                 magnetostrictive, 
                   
                 resulting from 
                 IJ35, IJ36, IJ37, 
               
               
                   
                 or other 
                   
                 high temperature 
                 IJ38, IJ39, IJ42, 
               
               
                   
                 mechanism. The 
                   
                 or high stress 
                 IJ43, IJ44 
               
               
                   
                 bend actuator 
                   
                 during formation 
               
               
                   
                 converts a high 
               
               
                   
                 force low travel 
               
               
                   
                 actuator 
               
               
                   
                 mechanism to high 
               
               
                   
                 travel, lower force 
               
               
                   
                 mechanism. 
               
               
                 Transient 
                 A trilayer bend 
                 Very good 
                 High stresses 
                 IJ40, IJ41 
               
               
                 bend 
                 actuator where the 
                 temperature 
                 are involved 
               
               
                 actuator 
                 two outside layers 
                 stability 
                 Care must be 
               
               
                   
                 are identical. This 
                 High speed, as 
                 taken that the 
               
               
                   
                 cancels bend due 
                 a new drop can 
                 materials do not 
               
               
                   
                 to ambient 
                 be fired before 
                 delaminate 
               
               
                   
                 temperature and 
                 heat dissipates 
               
               
                   
                 residual stress. The 
                 Cancels 
               
               
                   
                 actuator only 
                 residual stress of 
               
               
                   
                 responds to 
                 formation 
               
               
                   
                 transient heating of 
               
               
                   
                 one side or the 
               
               
                   
                 other. 
               
               
                 Reverse 
                 The actuator loads 
                 Better 
                 Fabrication 
                 IJ05, IJ11 
               
               
                 spring 
                 a spring. When the 
                 coupling to the 
                 complexity 
               
               
                   
                 actuator is turned 
                 ink 
                 High stress in 
               
               
                   
                 off, the spring 
                   
                 the spring 
               
               
                   
                 releases. This can 
               
               
                   
                 reverse the 
               
               
                   
                 force/distance 
               
               
                   
                 curve of the 
               
               
                   
                 actuator to make it 
               
               
                   
                 compatible with 
               
               
                   
                 the force/time 
               
               
                   
                 requirements of 
               
               
                   
                 the drop ejection. 
               
               
                 Actuator 
                 A series of thin 
                 Increased 
                 Increased 
                 Some 
               
               
                 stack 
                 actuators are 
                 travel 
                 fabrication 
                 piezoelectric ink 
               
               
                   
                 stacked. This can 
                 Reduced drive 
                 complexity 
                 jets 
               
               
                   
                 be appropriate 
                 voltage 
                 Increased 
                 IJ04 
               
               
                   
                 where actuators 
                   
                 possibility of 
               
               
                   
                 require high 
                   
                 short circuits due 
               
               
                   
                 electric field 
                   
                 to pinholes 
               
               
                   
                 strength, such as 
               
               
                   
                 electrostatic and 
               
               
                   
                 piezoelectric 
               
               
                   
                 actuators. 
               
               
                 Multiple 
                 Multiple smaller 
                 Increases the 
                 Actuator 
                 IJ12, IJ13, 
               
               
                 actuators 
                 actuators are used 
                 force available 
                 forces may not 
                 IJ18, IJ20, IJ22, 
               
               
                   
                 simultaneously to 
                 from an actuator 
                 add linearly, 
                 IJ28, IJ42, IJ43 
               
               
                   
                 move the ink. Each 
                 Multiple 
                 reducing 
               
               
                   
                 actuator need 
                 actuators can be 
                 efficiency 
               
               
                   
                 provide only a 
                 positioned to 
               
               
                   
                 portion of the 
                 control ink flow 
               
               
                   
                 force required. 
                 accurately 
               
               
                 Linear 
                 A linear spring is 
                 Matches low 
                 Requires print 
                 IJ15 
               
               
                 Spring 
                 used to transform a 
                 travel actuator 
                 head area for the 
               
               
                   
                 motion with small 
                 with higher 
                 spring 
               
               
                   
                 travel and high 
                 travel 
               
               
                   
                 force into a longer 
                 requirements 
               
               
                   
                 travel, lower force 
                 Non-contact 
               
               
                   
                 motion. 
                 method of 
               
               
                   
                   
                 motion 
               
               
                   
                   
                 transformation 
               
               
                 Coiled 
                 A bend actuator is 
                 Increases 
                 Generally 
                 IJ17, IJ21, 
               
               
                 actuator 
                 coiled to provide 
                 travel 
                 restricted to 
                 IJ34, IJ35 
               
               
                   
                 greater travel in a 
                 Reduces chip 
                 planar 
               
               
                   
                 reduced chip area. 
                 area 
                 implementations 
               
               
                   
                   
                 Planar 
                 due to extreme 
               
               
                   
                   
                 implementations 
                 fabrication 
               
               
                   
                   
                 are relatively 
                 difficulty in 
               
               
                   
                   
                 easy to fabricate. 
                 other 
               
               
                   
                   
                   
                 orientations. 
               
               
                 Flexure 
                 A bend actuator 
                 Simple means 
                 Care must be 
                 IJ10, IJ19, 
               
               
                 bend 
                 has a small region 
                 of increasing 
                 taken not to 
                 IJ33 
               
               
                 actuator 
                 near the fixture 
                 travel of a bend 
                 exceed the 
               
               
                   
                 point, which flexes 
                 actuator 
                 elastic limit in 
               
               
                   
                 much more readily 
                   
                 the flexure area 
               
               
                   
                 than the remainder 
                   
                 Stress 
               
               
                   
                 of the actuator. 
                   
                 distribution is 
               
               
                   
                 The actuator 
                   
                 very uneven 
               
               
                   
                 flexing is 
                   
                 Difficult to 
               
               
                   
                 effectively 
                   
                 accurately model 
               
               
                   
                 converted from an 
                   
                 with finite 
               
               
                   
                 even coiling to an 
                   
                 element analysis 
               
               
                   
                 angular bend, 
               
               
                   
                 resulting in greater 
               
               
                   
                 travel of the 
               
               
                   
                 actuator tip. 
               
               
                 Catch 
                 The actuator 
                 Very low 
                 Complex 
                 IJ10 
               
               
                   
                 controls a small 
                 actuator energy 
                 construction 
               
               
                   
                 catch. The catch 
                 Very small 
                 Requires 
               
               
                   
                 either enables or 
                 actuator size 
                 external force 
               
               
                   
                 disables movement 
                   
                 Unsuitable for 
               
               
                   
                 of an ink pusher 
                   
                 pigmented inks 
               
               
                   
                 that is controlled 
               
               
                   
                 in a bulk manner. 
               
               
                 Gears 
                 Gears can be used 
                 Low force, 
                 Moving parts 
                 IJ13 
               
               
                   
                 to increase travel 
                 low travel 
                 are required 
               
               
                   
                 at the expense of 
                 actuators can be 
                 Several 
               
               
                   
                 duration. Circular 
                 used 
                 actuator cycles 
               
               
                   
                 gears, rack and 
                 Can be 
                 are required 
               
               
                   
                 pinion, ratchets, 
                 fabricated using 
                 More complex 
               
               
                   
                 and other gearing 
                 standard surface 
                 drive electronics 
               
               
                   
                 methods can be 
                 MEMS 
                 Complex 
               
               
                   
                 used. 
                 processes 
                 construction 
               
               
                   
                   
                   
                 Friction, 
               
               
                   
                   
                   
                 friction, and 
               
               
                   
                   
                   
                 wear are 
               
               
                   
                   
                   
                 possible 
               
               
                 Buckle 
                 A buckle plate can 
                 Very fast 
                 Must stay 
                 S. Hirata et al, 
               
               
                 plate 
                 be used to change 
                 movement 
                 within elastic 
                 “An Ink-jet 
               
               
                   
                 a slow actuator 
                 achievable 
                 limits of the 
                 Head Using 
               
               
                   
                 into a fast motion. 
                   
                 materials for 
                 Diaphragm 
               
               
                   
                 It can also convert 
                   
                 long device life 
                 Microactuator”, 
               
               
                   
                 a high force, low 
                   
                 High stresses 
                 Proc. IEEE 
               
               
                   
                 travel actuator into 
                   
                 involved 
                 MEMS, February 
               
               
                   
                 a high travel, 
                   
                 Generally 
                 1996, pp 418-423. 
               
               
                   
                 medium force 
                   
                 high power 
                 IJ18, IJ27 
               
               
                   
                 motion. 
                   
                 requirement 
               
               
                 Tapered 
                 A tapered 
                 Linearizes the 
                 Complex 
                 IJ14 
               
               
                 magnetic 
                 magnetic pole can 
                 magnetic 
                 construction 
               
               
                 pole 
                 increase travel at 
                 force/distance 
               
               
                   
                 the expense of 
                 curve 
               
               
                   
                 force. 
               
               
                 Lever 
                 A lever and 
                 Matches low 
                 High stress 
                 IJ32, IJ36, 
               
               
                   
                 fulcrum is used to 
                 travel actuator 
                 around the 
                 IJ37 
               
               
                   
                 transform a motion 
                 with higher 
                 fulcrum 
               
               
                   
                 with small travel 
                 travel 
               
               
                   
                 and high force into 
                 requirements 
               
               
                   
                 a motion with 
                 Fulcrum area 
               
               
                   
                 longer travel and 
                 has no linear 
               
               
                   
                 lower force. The 
                 movement, and 
               
               
                   
                 lever can also 
                 can be used for a 
               
               
                   
                 reverse the 
                 fluid seal 
               
               
                   
                 direction of travel. 
               
               
                 Rotary 
                 The actuator is 
                 High 
                 Complex 
                 IJ28 
               
               
                 impeller 
                 connected to a 
                 mechanical 
                 construction 
               
               
                   
                 rotary impeller. A 
                 advantage 
                 Unsuitable for 
               
               
                   
                 small angular 
                 The ratio of 
                 pigmented inks 
               
               
                   
                 deflection of the 
                 force to travel of 
               
               
                   
                 actuator results in 
                 the actuator can 
               
               
                   
                 a rotation of the 
                 be matched to 
               
               
                   
                 impeller vanes, 
                 the nozzle 
               
               
                   
                 which push the ink 
                 requirements by 
               
               
                   
                 against stationary 
                 varying the 
               
               
                   
                 vanes and out of 
                 number of 
               
               
                   
                 the nozzle. 
                 impeller vanes 
               
               
                 Acoustic 
                 A refractive or 
                 No moving 
                 Large area 
                 1993 
               
               
                 lens 
                 diffractive (e.g. 
                 parts 
                 required 
                 Hadimioglu et 
               
               
                   
                 zone plate) 
                   
                 Only relevant 
                 al, EUP 550,192 
               
               
                   
                 acoustic lens is 
                   
                 for acoustic ink 
                 1993 Elrod et 
               
               
                   
                 used to concentrate 
                   
                 jets 
                 al, EUP 572,220 
               
               
                   
                 sound waves. 
               
               
                 Sharp 
                 A sharp point is 
                 Simple 
                 Difficult to 
                 Tone-jet 
               
               
                 conductive 
                 used to concentrate 
                 construction 
                 fabricate using 
               
               
                 point 
                 an electrostatic 
                   
                 standard VLSI 
               
               
                   
                 field. 
                   
                 processes for a 
               
               
                   
                   
                   
                 surface ejecting 
               
               
                   
                   
                   
                 ink-jet 
               
               
                   
                   
                   
                 Only relevant 
               
               
                   
                   
                   
                 for electrostatic 
               
               
                   
                   
                   
                 ink jets 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 ACTUATOR MOTION 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Volume 
                 The volume of the 
                 Simple 
                 High energy is 
                 Hewlett- 
               
               
                 expansion 
                 actuator changes, 
                 construction in 
                 typically 
                 Packard Thermal 
               
               
                   
                 pushing the ink in 
                 the case of 
                 required to 
                 Ink jet 
               
               
                   
                 all directions. 
                 thermal ink jet 
                 achieve volume 
                 Canon 
               
               
                   
                   
                   
                 expansion. This 
                 Bubblejet 
               
               
                   
                   
                   
                 leads to thermal 
               
               
                   
                   
                   
                 stress, cavitation, 
               
               
                   
                   
                   
                 and kogation in 
               
               
                   
                   
                   
                 thermal ink jet 
               
               
                   
                   
                   
                 implementations 
               
               
                 Linear, 
                 The actuator 
                 Efficient 
                 High 
                 IJ01, IJ02, 
               
               
                 normal to 
                 moves in a 
                 coupling to ink 
                 fabrication 
                 IJ04, IJ07, IJ11, 
               
               
                 chip 
                 direction normal to 
                 drops ejected 
                 complexity may 
                 IJ14 
               
               
                 surface 
                 the print head 
                 normal to the 
                 be required to 
               
               
                   
                 surface. The 
                 surface 
                 achieve 
               
               
                   
                 nozzle is typically 
                   
                 perpendicular 
               
               
                   
                 in the line of 
                   
                 motion 
               
               
                   
                 movement. 
               
               
                 Parallel to 
                 The actuator 
                 Suitable for 
                 Fabrication 
                 IJ12, IJ13, 
               
               
                 chip 
                 moves parallel to 
                 planar 
                 complexity 
                 IJ15, IJ33,, IJ34, 
               
               
                 surface 
                 the print head 
                 fabrication 
                 Friction 
                 IJ35, IJ36 
               
               
                   
                 surface. Drop 
                   
                 Stiction 
               
               
                   
                 ejection may still 
               
               
                   
                 be normal to the 
               
               
                   
                 surface. 
               
               
                 Membrane 
                 An actuator with a 
                 The effective 
                 Fabrication 
                 1982 Howkins 
               
               
                 push 
                 high force but 
                 area of the 
                 complexity 
                 U.S. Pat. No. 4,459,601 
               
               
                   
                 small area is used 
                 actuator 
                 Actuator size 
               
               
                   
                 to push a stiff 
                 becomes the 
                 Difficulty of 
               
               
                   
                 membrane that is 
                 membrane area 
                 integration in a 
               
               
                   
                 in contact with the 
                   
                 VLSI process 
               
               
                   
                 ink. 
               
               
                 Rotary 
                 The actuator 
                 Rotary levers 
                 Device 
                 IJ05, IJ08, 
               
               
                   
                 causes the rotation 
                 may be used to 
                 complexity 
                 IJ13, IJ28 
               
               
                   
                 of some element, 
                 increase travel 
                 May have 
               
               
                   
                 such a grill or 
                 Small chip 
                 friction at a pivot 
               
               
                   
                 impeller 
                 area 
                 point 
               
               
                   
                   
                 requirements 
               
               
                 Bend 
                 The actuator bends 
                 A very small 
                 Requires the 
                 1970 Kyser et 
               
               
                   
                 when energized. 
                 change in 
                 actuator to be 
                 al U.S. Pat. No. 
               
               
                   
                 This may be due to 
                 dimensions can 
                 made from at 
                 3,946,398 
               
               
                   
                 differential 
                 be converted to a 
                 least two distinct 
                 1973 Stemme 
               
               
                   
                 thermal expansion, 
                 large motion. 
                 layers, or to have 
                 U.S. Pat. No. 3,747,120 
               
               
                   
                 piezoelectric 
                   
                 a thermal 
                 IJ03, IJ09, 
               
               
                   
                 expansion, 
                   
                 difference across 
                 IJ10, IJ19, IJ23, 
               
               
                   
                 magnetostriction, 
                   
                 the actuator 
                 IJ24, IJ25, IJ29, 
               
               
                   
                 or other form of 
                   
                   
                 IJ30, IJ31, IJ33, 
               
               
                   
                 relative 
                   
                   
                 IJ34, IJ35 
               
               
                   
                 dimensional 
               
               
                   
                 change. 
               
               
                 Swivel 
                 The actuator 
                 Allows 
                 Inefficient 
                 IJ06 
               
               
                   
                 swivels around a 
                 operation where 
                 coupling to the 
               
               
                   
                 central pivot. This 
                 the net linear 
                 ink motion 
               
               
                   
                 motion is suitable 
                 force on the 
               
               
                   
                 where there are 
                 paddle is zero 
               
               
                   
                 opposite forces 
                 Small chip 
               
               
                   
                 applied to opposite 
                 area 
               
               
                   
                 sides of the paddle, 
                 requirements 
               
               
                   
                 e.g. Lorenz force. 
               
               
                 Straighten 
                 The actuator is 
                 Can be used 
                 Requires 
                 IJ26, IJ32 
               
               
                   
                 normally bent, and 
                 with shape 
                 careful balance 
               
               
                   
                 straightens when 
                 memory alloys 
                 of stresses to 
               
               
                   
                 energized. 
                 where the 
                 ensure that the 
               
               
                   
                   
                 austenic phase is 
                 quiescent bend is 
               
               
                   
                   
                 planar 
                 accurate 
               
               
                 Double 
                 The actuator bends 
                 One actuator 
                 Difficult to 
                 IJ36, IJ37, 
               
               
                 bend 
                 in one direction 
                 can be used to 
                 make the drops 
                 IJ38 
               
               
                   
                 when one element 
                 power two 
                 ejected by both 
               
               
                   
                 is energized, and 
                 nozzles. 
                 bend directions 
               
               
                   
                 bends the other 
                 Reduced chip 
                 identical. 
               
               
                   
                 way when another 
                 size. 
                 A small 
               
               
                   
                 element is 
                 Not sensitive 
                 efficiency loss 
               
               
                   
                 energized. 
                 to ambient 
                 compared to 
               
               
                   
                   
                 temperature 
                 equivalent single 
               
               
                   
                   
                   
                 bend actuators. 
               
               
                 Shear 
                 Energizing the 
                 Can increase 
                 Not readily 
                 1985 Fishbeck 
               
               
                   
                 actuator causes a 
                 the effective 
                 applicable to 
                 U.S. Pat. No. 4,584,590 
               
               
                   
                 shear motion in the 
                 travel of 
                 other actuator 
               
               
                   
                 actuator material. 
                 piezoelectric 
                 mechanisms 
               
               
                   
                   
                 actuators 
               
               
                 Radial 
                 The actuator 
                 Relatively 
                 High force 
                 1970 Zoltan 
               
               
                 constriction 
                 squeezes an ink 
                 easy to fabricate 
                 required 
                 U.S. Pat. No. 3,683,212 
               
               
                   
                 reservoir, forcing 
                 single nozzles 
                 Inefficient 
               
               
                   
                 ink from a 
                 from glass 
                 Difficult to 
               
               
                   
                 constricted nozzle. 
                 tubing as 
                 integrate with 
               
               
                   
                   
                 macroscopic 
                 VLSI processes 
               
               
                   
                   
                 structures 
               
               
                 Coil/ 
                 A coiled actuator 
                 Easy to 
                 Difficult to 
                 IJ17, IJ21, 
               
               
                 uncoil 
                 uncoils or coils 
                 fabricate as a 
                 fabricate for 
                 IJ34, IJ35 
               
               
                   
                 more tightly. The 
                 planar VLSI 
                 non-planar 
               
               
                   
                 motion of the free 
                 process 
                 devices 
               
               
                   
                 end of the actuator 
                 Small area 
                 Poor out-of- 
               
               
                   
                 ejects the ink. 
                 required, 
                 plane stiffness 
               
               
                   
                   
                 therefore low 
               
               
                   
                   
                 cost 
               
               
                 Bow 
                 The actuator bows 
                 Can increase 
                 Maximum 
                 IJ16, IJ18, 
               
               
                   
                 (or buckles) in the 
                 the speed of 
                 travel is 
                 IJ27 
               
               
                   
                 middle when 
                 travel 
                 constrained 
               
               
                   
                 energized. 
                 Mechanically 
                 High force 
               
               
                   
                   
                 rigid 
                 required 
               
               
                 Push-Pull 
                 Two actuators 
                 The structure 
                 Not readily 
                 IJ18 
               
               
                   
                 control a shutter. 
                 is pinned at both 
                 suitable for ink 
               
               
                   
                 One actuator pulls 
                 ends, so has a 
                 jets which 
               
               
                   
                 the shutter, and the 
                 high out-of- 
                 directly push the 
               
               
                   
                 other pushes it. 
                 plane rigidity 
                 ink 
               
               
                 Curl 
                 A set of actuators 
                 Good fluid 
                 Design 
                 IJ20, IJ42 
               
               
                 inwards 
                 curl inwards to 
                 flow to the 
                 complexity 
               
               
                   
                 reduce the volume 
                 region behind 
               
               
                   
                 of ink that they 
                 the actuator 
               
               
                   
                 enclose. 
                 increases 
               
               
                   
                   
                 efficiency 
               
               
                 Curl 
                 A set of actuators 
                 Relatively 
                 Relatively 
                 IJ43 
               
               
                 outwards 
                 curl outwards, 
                 simple 
                 large chip area 
               
               
                   
                 pressurizing ink in 
                 construction 
               
               
                   
                 a chamber 
               
               
                   
                 surrounding the 
               
               
                   
                 actuators, and 
               
               
                   
                 expelling ink from 
               
               
                   
                 a nozzle in the 
               
               
                   
                 chamber. 
               
               
                 Iris 
                 Multiple vanes 
                 High 
                 High 
                 IJ22 
               
               
                   
                 enclose a volume 
                 efficiency 
                 fabrication 
               
               
                   
                 of ink. These 
                 Small chip 
                 complexity 
               
               
                   
                 simultaneously 
                 area 
                 Not suitable 
               
               
                   
                 rotate, reducing 
                   
                 for pigmented 
               
               
                   
                 the volume 
                   
                 inks 
               
               
                   
                 between the vanes. 
               
               
                 Acoustic 
                 The actuator 
                 The actuator 
                 Large area 
                 1993 
               
               
                 vibration 
                 vibrates at a high 
                 can be 
                 required for 
                 Hadimioglu et 
               
               
                   
                 frequency. 
                 physically 
                 efficient 
                 al, EUP 550,192 
               
               
                   
                   
                 distant from the 
                 operation at 
                 1993 Elrod et 
               
               
                   
                   
                 ink 
                 useful 
                 al, EUP 572,220 
               
               
                   
                   
                   
                 frequencies 
               
               
                   
                   
                   
                 Acoustic 
               
               
                   
                   
                   
                 coupling and 
               
               
                   
                   
                   
                 crosstalk 
               
               
                   
                   
                   
                 Complex 
               
               
                   
                   
                   
                 drive circuitry 
               
               
                   
                   
                   
                 Poor control 
               
               
                   
                   
                   
                 of drop volume 
               
               
                   
                   
                   
                 and position 
               
               
                 None 
                 In various ink jet 
                 No moving 
                 Various other 
                 Silverbrook, 
               
               
                   
                 designs the 
                 parts 
                 tradeoffs are 
                 EP 0771 658 A2 
               
               
                   
                 actuator does not 
                   
                 required to 
                 and related 
               
               
                   
                 move. 
                   
                 eliminate 
                 patent 
               
               
                   
                   
                   
                 moving parts 
                 applications 
               
               
                   
                   
                   
                   
                 Tone-jet 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 NOZZLE REFILL METHOD 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                 This is the normal 
                 Fabrication 
                 Low speed 
                 Thermal ink 
               
               
                 tension 
                 way that ink jets 
                 simplicity 
                 Surface 
                 jet 
               
               
                   
                 are refilled. After 
                 Operational 
                 tension force 
                 Piezoelectric 
               
               
                   
                 the actuator is 
                 simplicity 
                 relatively small 
                 ink jet 
               
               
                   
                 energized, it 
                   
                 compared to 
                 IJ01-IJ07, 
               
               
                   
                 typically returns 
                   
                 actuator force 
                 IJ10-IJ14, IJ16, 
               
               
                   
                 rapidly to its 
                   
                 Long refill 
                 IJ20, IJ22-IJ45 
               
               
                   
                 normal position. 
                   
                 time usually 
               
               
                   
                 This rapid return 
                   
                 dominates the 
               
               
                   
                 sucks in air 
                   
                 total repetition 
               
               
                   
                 through the nozzle 
                   
                 rate 
               
               
                   
                 opening. The ink 
               
               
                   
                 surface tension at 
               
               
                   
                 the nozzle then 
               
               
                   
                 exerts a small 
               
               
                   
                 force restoring the 
               
               
                   
                 meniscus to a 
               
               
                   
                 minimum area. 
               
               
                   
                 This force refills 
               
               
                   
                 the nozzle. 
               
               
                 Shuttered 
                 Ink to the nozzle 
                 High speed 
                 Requires 
                 IJ08, IJ13, 
               
               
                 oscillating 
                 chamber is 
                 Low actuator 
                 common ink 
                 IJ15, IJ17, IJ18, 
               
               
                 ink 
                 provided at a 
                 energy, as the 
                 pressure 
                 IJ19, IJ21 
               
               
                 pressure 
                 pressure that 
                 actuator need 
                 oscillator 
               
               
                   
                 oscillates at twice 
                 only open or 
                 May not be 
               
               
                   
                 the drop ejection 
                 close the shutter, 
                 suitable for 
               
               
                   
                 frequency. When a 
                 instead of 
                 pigmented inks 
               
               
                   
                 drop is to be 
                 ejecting the ink 
               
               
                   
                 ejected, the shutter 
                 drop 
               
               
                   
                 is opened for 3 
               
               
                   
                 half cycles: drop 
               
               
                   
                 ejection, actuator 
               
               
                   
                 return, and refill. 
               
               
                   
                 The shutter is then 
               
               
                   
                 closed to prevent 
               
               
                   
                 the nozzle 
               
               
                   
                 chamber emptying 
               
               
                   
                 during the next 
               
               
                   
                 negative pressure 
               
               
                   
                 cycle. 
               
               
                 Refill 
                 After the main 
                 High speed, as 
                 Requires two 
                 IJ09 
               
               
                 actuator 
                 actuator has 
                 the nozzle is 
                 independent 
               
               
                   
                 ejected a drop a 
                 actively refilled 
                 actuators per 
               
               
                   
                 second (refill) 
                   
                 nozzle 
               
               
                   
                 actuator is 
               
               
                   
                 energized. The 
               
               
                   
                 refill actuator 
               
               
                   
                 pushes ink into the 
               
               
                   
                 nozzle chamber. 
               
               
                   
                 The refill actuator 
               
               
                   
                 returns slowly, to 
               
               
                   
                 prevent its return 
               
               
                   
                 from emptying the 
               
               
                   
                 chamber again. 
               
               
                 Positive 
                 The ink is held a 
                 High refill 
                 Surface spill 
                 Silverbrook, 
               
               
                 ink 
                 slight positive 
                 rate, therefore a 
                 must be 
                 EP 0771 658 A2 
               
               
                 pressure 
                 pressure. After the 
                 high drop 
                 prevented 
                 and related 
               
               
                   
                 ink drop is ejected, 
                 repetition rate is 
                 Highly 
                 patent 
               
               
                   
                 the nozzle 
                 possible 
                 hydrophobic 
                 applications 
               
               
                   
                 chamber fills 
                   
                 print head 
                 Alternative 
               
               
                   
                 quickly as surface 
                   
                 surfaces are 
                 for:, IJ01-IJ07, 
               
               
                   
                 tension and ink 
                   
                 required 
                 IJ10-IJ14, IJ16, 
               
               
                   
                 pressure both 
                   
                   
                 IJ20, IJ22-IJ45 
               
               
                   
                 operate to refill the 
               
               
                   
                 nozzle. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 METHOD OF RESTRICTING BACK-FLOW THROUGH INLET 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Long inlet 
                 The ink inlet 
                 Design 
                 Restricts refill 
                 Thermal ink 
               
               
                 channel 
                 channel to the 
                 simplicity 
                 rate 
                 jet 
               
               
                   
                 nozzle chamber is 
                 Operational 
                 May result in 
                 Piezoelectric 
               
               
                   
                 made long and 
                 simplicity 
                 a relatively large 
                 ink jet 
               
               
                   
                 relatively narrow, 
                 Reduces 
                 chip area 
                 IJ42, IJ43 
               
               
                   
                 relying on viscous 
                 crosstalk 
                 Only partially 
               
               
                   
                 drag to reduce 
                   
                 effective 
               
               
                   
                 inlet back-flow. 
               
               
                 Positive 
                 The ink is under a 
                 Drop selection 
                 Requires a 
                 Silverbrook, 
               
               
                 ink 
                 positive pressure, 
                 and separation 
                 method (such as 
                 EP 0771 658 A2 
               
               
                 pressure 
                 so that in the 
                 forces can be 
                 a nozzle rim or 
                 and related 
               
               
                   
                 quiescent state 
                 reduced 
                 effective 
                 patent 
               
               
                   
                 some of the ink 
                 Fast refill time 
                 hydrophobizing, 
                 applications 
               
               
                   
                 drop already 
                   
                 or both) to 
                 Possible 
               
               
                   
                 protrudes from the 
                   
                 prevent flooding 
                 operation of the 
               
               
                   
                 nozzle. 
                   
                 of the ejection 
                 following: IJ01-IJ07, 
               
               
                   
                 This reduces the 
                   
                 surface of the 
                 IJ09-IJ12, 
               
               
                   
                 pressure in the 
                   
                 print head. 
                 IJ14, IJ16, IJ20, 
               
               
                   
                 nozzle chamber 
                   
                   
                 IJ22,, IJ23-IJ34, 
               
               
                   
                 which is required 
                   
                   
                 IJ36-IJ41, IJ44 
               
               
                   
                 to eject a certain 
               
               
                   
                 volume of ink. The 
               
               
                   
                 reduction in 
               
               
                   
                 chamber pressure 
               
               
                   
                 results in a 
               
               
                   
                 reduction in ink 
               
               
                   
                 pushed out through 
               
               
                   
                 the inlet. 
               
               
                 Baffle 
                 One or more 
                 The refill rate 
                 Design 
                 HP Thermal 
               
               
                   
                 baffles are placed 
                 is not as 
                 complexity 
                 Ink Jet 
               
               
                   
                 in the inlet ink 
                 restricted as the 
                 May increase 
                 Tektronix 
               
               
                   
                 flow. When the 
                 long inlet 
                 fabrication 
                 piezoelectric ink 
               
               
                   
                 actuator is 
                 method. 
                 complexity (e.g. 
                 jet 
               
               
                   
                 energized, the 
                 Reduces 
                 Tektronix hot 
               
               
                   
                 rapid ink 
                 crosstalk 
                 melt 
               
               
                   
                 movement creates 
                   
                 Piezoelectric 
               
               
                   
                 eddies which 
                   
                 print heads). 
               
               
                   
                 restrict the flow 
               
               
                   
                 through the inlet. 
               
               
                   
                 The slower refill 
               
               
                   
                 process is 
               
               
                   
                 unrestricted, and 
               
               
                   
                 does not result in 
               
               
                   
                 eddies. 
               
               
                 Flexible 
                 In this method 
                 Significantly 
                 Not applicable 
                 Canon 
               
               
                 flap 
                 recently disclosed 
                 reduces back- 
                 to most ink jet 
               
               
                 restricts 
                 by Canon, the 
                 flow for edge- 
                 configurations 
               
               
                 inlet 
                 expanding actuator 
                 shooter thermal 
                 Increased 
               
               
                   
                 (bubble) pushes on 
                 ink jet devices 
                 fabrication 
               
               
                   
                 a flexible flap that 
                   
                 complexity 
               
               
                   
                 restricts the inlet. 
                   
                 Inelastic 
               
               
                   
                   
                   
                 deformation of 
               
               
                   
                   
                   
                 polymer flap 
               
               
                   
                   
                   
                 results in creep 
               
               
                   
                   
                   
                 over extended 
               
               
                   
                   
                   
                 use 
               
               
                 Inlet filter 
                 A filter is located 
                 Additional 
                 Restricts refill 
                 IJ04, IJ12, 
               
               
                   
                 between the ink 
                 advantage of ink 
                 rate 
                 IJ24, IJ27, IJ29, 
               
               
                   
                 inlet and the 
                 filtration 
                 May result in 
                 IJ30 
               
               
                   
                 nozzle chamber. 
                 Ink filter may 
                 complex 
               
               
                   
                 The filter has a 
                 be fabricated 
                 construction 
               
               
                   
                 multitude of small 
                 with no 
               
               
                   
                 holes or slots, 
                 additional 
               
               
                   
                 restricting ink 
                 process steps 
               
               
                   
                 flow. The filter 
               
               
                   
                 also removes 
               
               
                   
                 particles which 
               
               
                   
                 may block the 
               
               
                   
                 nozzle. 
               
               
                 Small 
                 The ink inlet 
                 Design 
                 Restricts refill 
                 IJ02, IJ37, 
               
               
                 inlet 
                 channel to the 
                 simplicity 
                 rate 
                 IJ44 
               
               
                 compared 
                 nozzle chamber 
                   
                 May result in 
               
               
                 to nozzle 
                 has a substantially 
                   
                 a relatively large 
               
               
                   
                 smaller cross 
                   
                 chip area 
               
               
                   
                 section than that of 
                   
                 Only partially 
               
               
                   
                 the nozzle, 
                   
                 effective 
               
               
                   
                 resulting in easier 
               
               
                   
                 ink egress out of 
               
               
                   
                 the nozzle than out 
               
               
                   
                 of the inlet. 
               
               
                 Inlet 
                 A secondary 
                 Increases 
                 Requires 
                 IJ09 
               
               
                 shutter 
                 actuator controls 
                 speed of the ink- 
                 separate refill 
               
               
                   
                 the position of a 
                 jet print head 
                 actuator and 
               
               
                   
                 shutter, closing off 
                 operation 
                 drive circuit 
               
               
                   
                 the ink inlet when 
               
               
                   
                 the main actuator 
               
               
                   
                 is energized. 
               
               
                 The inlet 
                 The method avoids 
                 Back-flow 
                 Requires 
                 IJ01, IJ03, 
               
               
                 is located 
                 the problem of 
                 problem is 
                 careful design to 
                 IJ05, IJ06, IJ07, 
               
               
                 behind 
                 inlet back-flow by 
                 eliminated 
                 minimize the 
                 IJ10, IJ11, IJ14, 
               
               
                 the ink- 
                 arranging the ink- 
                   
                 negative 
                 IJ16, IJ22, IJ23, 
               
               
                 pushing 
                 pushing surface of 
                   
                 pressure behind 
                 IJ25, IJ28, IJ31, 
               
               
                 surface 
                 the actuator 
                   
                 the paddle 
                 IJ32, IJ33, IJ34, 
               
               
                   
                 between the inlet 
                   
                   
                 IJ35, IJ36, IJ39, 
               
               
                   
                 and the nozzle. 
                   
                   
                 IJ40, IJ41 
               
               
                 Part of 
                 The actuator and a 
                 Significant 
                 Small increase 
                 IJ07, IJ20, 
               
               
                 the 
                 wall of the ink 
                 reductions in 
                 in fabrication 
                 IJ26, IJ38 
               
               
                 actuator 
                 chamber are 
                 back-flow can be 
                 complexity 
               
               
                 moves to 
                 arranged so that 
                 achieved 
               
               
                 shut off 
                 the motion of the 
                 Compact 
               
               
                 the inlet 
                 actuator closes off 
                 designs possible 
               
               
                   
                 the inlet. 
               
               
                 Nozzle 
                 In some 
                 Ink back-flow 
                 None related 
                 Silverbrook, 
               
               
                 actuator 
                 configurations of 
                 problem is 
                 to ink back-flow 
                 EP 0771 658 A2 
               
               
                 does not 
                 ink jet, there is no 
                 eliminated 
                 on actuation 
                 and related 
               
               
                 result in 
                 expansion or 
                   
                   
                 patent 
               
               
                 ink back- 
                 movement of an 
                   
                   
                 applications 
               
               
                 flow 
                 actuator which 
                   
                   
                 Valve-jet 
               
               
                   
                 may cause ink 
                   
                   
                 Tone-jet 
               
               
                   
                 back-flow through 
               
               
                   
                 the inlet. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 NOZZLE CLEARING METHOD 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Normal 
                 All of the nozzles 
                 No added 
                 May not be 
                 Most ink jet 
               
               
                 nozzle 
                 are fired 
                 complexity on 
                 sufficient to 
                 systems 
               
               
                 firing 
                 periodically, 
                 the print head 
                 displace dried 
                 IJ01, IJ02, 
               
               
                   
                 before the ink has 
                   
                 ink 
                 IJ03, IJ04, IJ05, 
               
               
                   
                 a chance to dry. 
                   
                   
                 IJ06, IJ07, IJ09, 
               
               
                   
                 When not in use 
                   
                   
                 IJ10, IJ11, IJ12, 
               
               
                   
                 the nozzles are 
                   
                   
                 IJ14, IJ16, IJ20, 
               
               
                   
                 sealed (capped) 
                   
                   
                 IJ22, IJ23, IJ24, 
               
               
                   
                 against air. 
                   
                   
                 IJ25, IJ26, IJ27, 
               
               
                   
                 The nozzle firing 
                   
                   
                 IJ28, IJ29, IJ30, 
               
               
                   
                 is usually 
                   
                   
                 IJ31, IJ32, IJ33, 
               
               
                   
                 performed during a 
                   
                   
                 IJ34, IJ36, IJ37, 
               
               
                   
                 special clearing 
                   
                   
                 IJ38, IJ39, IJ40,, 
               
               
                   
                 cycle, after first 
                   
                   
                 IJ41, IJ42, IJ43, 
               
               
                   
                 moving the print 
                   
                   
                 IJ44,, IJ45 
               
               
                   
                 head to a cleaning 
               
               
                   
                 station. 
               
               
                 Extra 
                 In systems which 
                 Can be highly 
                 Requires 
                 Silverbrook, 
               
               
                 power to 
                 heat the ink, but do 
                 effective if the 
                 higher drive 
                 EP 0771 658 A2 
               
               
                 ink heater 
                 not boil it under 
                 heater is 
                 voltage for 
                 and related 
               
               
                   
                 normal situations, 
                 adjacent to the 
                 clearing 
                 patent 
               
               
                   
                 nozzle clearing can 
                 nozzle 
                 May require 
                 applications 
               
               
                   
                 be achieved by 
                   
                 larger drive 
               
               
                   
                 over-powering the 
                   
                 transistors 
               
               
                   
                 heater and boiling 
               
               
                   
                 ink at the nozzle. 
               
               
                 Rapid 
                 The actuator is 
                 Does not 
                 Effectiveness 
                 May be used 
               
               
                 succession 
                 fired in rapid 
                 require extra 
                 depends 
                 with: IJ01, IJ02, 
               
               
                 of 
                 succession. In 
                 drive circuits on 
                 substantially 
                 IJ03, IJ04, IJ05, 
               
               
                 actuator 
                 some 
                 the print head 
                 upon the 
                 IJ06, IJ07, IJ09, 
               
               
                 pulses 
                 configurations, this 
                 Can be readily 
                 configuration of 
                 IJ10, IJ11, IJ14, 
               
               
                   
                 may cause heat 
                 controlled and 
                 the ink jet nozzle 
                 IJ16, IJ20, IJ22, 
               
               
                   
                 build-up at the 
                 initiated by 
                   
                 IJ23, IJ24, IJ25, 
               
               
                   
                 nozzle which boils 
                 digital logic 
                   
                 IJ27, IJ28, IJ29, 
               
               
                   
                 the ink, clearing 
                   
                   
                 IJ30, IJ31, IJ32, 
               
               
                   
                 the nozzle. In other 
                   
                   
                 IJ33, IJ34, IJ36, 
               
               
                   
                 situations, it may 
                   
                   
                 IJ37, IJ38, IJ39, 
               
               
                   
                 cause sufficient 
                   
                   
                 IJ40, IJ41, IJ42, 
               
               
                   
                 vibrations to 
                   
                   
                 IJ43, IJ44, IJ45 
               
               
                   
                 dislodge clogged 
               
               
                   
                 nozzles. 
               
               
                 Extra 
                 Where an actuator 
                 A simple 
                 Not suitable 
                 May be used 
               
               
                 power to 
                 is not normally 
                 solution where 
                 where there is a 
                 with: IJ03, IJ09, 
               
               
                 ink 
                 driven to the limit 
                 applicable 
                 hard limit to 
                 IJ16, IJ20, IJ23, 
               
               
                 pushing 
                 of its motion, 
                   
                 actuator 
                 IJ24, IJ25, IJ27, 
               
               
                 actuator 
                 nozzle clearing 
                   
                 movement 
                 IJ29, IJ30, IJ31, 
               
               
                   
                 may be assisted by 
                   
                   
                 IJ32, IJ39, IJ40, 
               
               
                   
                 providing an 
                   
                   
                 IJ41, IJ42, IJ43, 
               
               
                   
                 enhanced drive 
                   
                   
                 IJ44, IJ45 
               
               
                   
                 signal to the 
               
               
                   
                 actuator. 
               
               
                 Acoustic 
                 An ultrasonic 
                 A high nozzle 
                 High 
                 IJ08, IJ13, 
               
               
                 resonance 
                 wave is applied to 
                 clearing 
                 implementation 
                 IJ15, IJ17, IJ18, 
               
               
                   
                 the ink chamber. 
                 capability can be 
                 cost if system 
                 IJ19, IJ21 
               
               
                   
                 This wave is of an 
                 achieved 
                 does not already 
               
               
                   
                 appropriate 
                 May be 
                 include an 
               
               
                   
                 amplitude and 
                 implemented at 
                 acoustic actuator 
               
               
                   
                 frequency to cause 
                 very low cost in 
               
               
                   
                 sufficient force at 
                 systems which 
               
               
                   
                 the nozzle to clear 
                 already include 
               
               
                   
                 blockages. This is 
                 acoustic 
               
               
                   
                 easiest to achieve 
                 actuators 
               
               
                   
                 if the ultrasonic 
               
               
                   
                 wave is at a 
               
               
                   
                 resonant frequency 
               
               
                   
                 of the ink cavity. 
               
               
                 Nozzle 
                 A microfabricated 
                 Can clear 
                 Accurate 
                 Silverbrook, 
               
               
                 clearing 
                 plate is pushed 
                 severely clogged 
                 mechanical 
                 EP 0771 658 A2 
               
               
                 plate 
                 against the 
                 nozzles 
                 alignment is 
                 and related 
               
               
                   
                 nozzles. The plate 
                   
                 required 
                 patent 
               
               
                   
                 has a post for 
                   
                 Moving parts 
                 applications 
               
               
                   
                 every nozzle. A 
                   
                 are required 
               
               
                   
                 post moves 
                   
                 There is risk 
               
               
                   
                 through each 
                   
                 of damage to the 
               
               
                   
                 nozzle, displacing 
                   
                 nozzles 
               
               
                   
                 dried ink. 
                   
                 Accurate 
               
               
                   
                   
                   
                 fabrication is 
               
               
                   
                   
                   
                 required 
               
               
                 Ink 
                 The pressure of the 
                 May be 
                 Requires 
                 May be used 
               
               
                 pressure 
                 ink is temporarily 
                 effective where 
                 pressure pump 
                 with all IJ series 
               
               
                 pulse 
                 increased so that 
                 other methods 
                 or other pressure 
                 ink jets 
               
               
                   
                 ink streams from 
                 cannot be used 
                 actuator 
               
               
                   
                 all of the nozzles. 
                   
                 Expensive 
               
               
                   
                 This may be used 
                   
                 Wasteful of 
               
               
                   
                 in conjunction 
                   
                 ink 
               
               
                   
                 with actuator 
               
               
                   
                 energizing. 
               
               
                 Print 
                 A flexible ‘blade’ 
                 Effective for 
                 Difficult to 
                 Many ink jet 
               
               
                 head 
                 is wiped across the 
                 planar print head 
                 use if print head 
                 systems 
               
               
                 wiper 
                 print head surface. 
                 surfaces 
                 surface is non- 
               
               
                   
                 The blade is 
                 Low cost 
                 planar or very 
               
               
                   
                 usually fabricated 
                   
                 fragile 
               
               
                   
                 from a flexible 
                   
                 Requires 
               
               
                   
                 polymer, e.g. 
                   
                 mechanical parts 
               
               
                   
                 rubber or synthetic 
                   
                 Blade can 
               
               
                   
                 elastomer. 
                   
                 wear out in high 
               
               
                   
                   
                   
                 volume print 
               
               
                   
                   
                   
                 systems 
               
               
                 Separate 
                 A separate heater 
                 Can be 
                 Fabrication 
                 Can be used 
               
               
                 ink 
                 is provided at the 
                 effective where 
                 complexity 
                 with many IJ 
               
               
                 boiling 
                 nozzle although 
                 other nozzle 
                   
                 series ink jets 
               
               
                 heater 
                 the normal drop e- 
                 clearing methods 
               
               
                   
                 ection mechanism 
                 cannot be used 
               
               
                   
                 does not require it. 
                 Can be 
               
               
                   
                 The heaters do not 
                 implemented at 
               
               
                   
                 require individual 
                 no additional 
               
               
                   
                 drive circuits, as 
                 cost in some ink 
               
               
                   
                 many nozzles can 
                 jet 
               
               
                   
                 be cleared 
                 configurations 
               
               
                   
                 simultaneously, 
               
               
                   
                 and no imaging is 
               
               
                   
                 required. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 NOZZLE PLATE CONSTRUCTION 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Electro- 
                 A nozzle plate is 
                 Fabrication 
                 High 
                 Hewlett 
               
               
                 formed 
                 separately 
                 simplicity 
                 temperatures and 
                 Packard Thermal 
               
               
                 nickel 
                 fabricated from 
                   
                 pressures are 
                 Ink jet 
               
               
                   
                 electroformed 
                   
                 required to bond 
               
               
                   
                 nickel, and bonded 
                   
                 nozzle plate 
               
               
                   
                 to the print head 
                   
                 Minimum 
               
               
                   
                 chip. 
                   
                 thickness 
               
               
                   
                   
                   
                 constraints 
               
               
                   
                   
                   
                 Differential 
               
               
                   
                   
                   
                 thermal 
               
               
                   
                   
                   
                 expansion 
               
               
                 Laser 
                 Individual nozzle 
                 No masks 
                 Each hole 
                 Canon 
               
               
                 ablated or 
                 holes are ablated 
                 required 
                 must be 
                 Bubblejet 
               
               
                 drilled 
                 by an intense UV 
                 Can be quite 
                 individually 
                 1988 Sercel et 
               
               
                 polymer 
                 laser in a nozzle 
                 fast 
                 formed 
                 al., SPIE, Vol. 
               
               
                   
                 plate, which is 
                 Some control 
                 Special 
                 998 Excimer 
               
               
                   
                 typically a 
                 over nozzle 
                 equipment 
                 Beam 
               
               
                   
                 polymer such as 
                 profile is 
                 required 
                 Applications, pp. 
               
               
                   
                 polyimide or 
                 possible 
                 Slow where 
                 76-83 
               
               
                   
                 polysulphone 
                 Equipment 
                 there are many 
                 1993 
               
               
                   
                   
                 required is 
                 thousands of 
                 Watanabe et al., 
               
               
                   
                   
                 relatively low 
                 nozzles per print 
                 U.S. Pat. No. 5,208,604 
               
               
                   
                   
                 cost 
                 head 
               
               
                   
                   
                   
                 May produce 
               
               
                   
                   
                   
                 thin burrs at exit 
               
               
                   
                   
                   
                 holes 
               
               
                 Silicon 
                 A separate nozzle 
                 High accuracy 
                 Two part 
                 K. Bean, 
               
               
                 micro- 
                 plate is 
                 is attainable 
                 construction 
                 IEEE 
               
               
                 machined 
                 micromachined 
                   
                 High cost 
                 Transactions on 
               
               
                   
                 from single crystal 
                   
                 Requires 
                 Electron 
               
               
                   
                 silicon, and 
                   
                 precision 
                 Devices, Vol. 
               
               
                   
                 bonded to the print 
                   
                 alignment 
                 ED-25, No. 10, 
               
               
                   
                 head wafer. 
                   
                 Nozzles may 
                 1978, pp 1185-1195 
               
               
                   
                   
                   
                 be clogged by 
                 Xerox 1990 
               
               
                   
                   
                   
                 adhesive 
                 Hawkins et al., 
               
               
                   
                   
                   
                   
                 U.S. Pat. No. 4,899,181 
               
               
                 Glass 
                 Fine glass 
                 No expensive 
                 Very small 
                 1970 Zoltan 
               
               
                 capillaries 
                 capillaries are 
                 equipment 
                 nozzle sizes are 
                 U.S. Pat. No. 3,683,212 
               
               
                   
                 drawn from glass 
                 required 
                 difficult to form 
               
               
                   
                 tubing. This 
                 Simple to 
                 Not suited for 
               
               
                   
                 method has been 
                 make single 
                 mass production 
               
               
                   
                 used for making 
                 nozzles 
               
               
                   
                 individual nozzles, 
               
               
                   
                 but is difficult to 
               
               
                   
                 use for bulk 
               
               
                   
                 manufacturing of 
               
               
                   
                 print heads with 
               
               
                   
                 thousands of 
               
               
                   
                 nozzles. 
               
               
                 Monolithic, 
                 The nozzle plate is 
                 High accuracy 
                 Requires 
                 Silverbrook, 
               
               
                 surface 
                 deposited as a 
                 (&lt;1 μm) 
                 sacrificial layer 
                 EP 0771 658 A2 
               
               
                 micro- 
                 layer using 
                 Monolithic 
                 under the nozzle 
                 and related 
               
               
                 machined 
                 standard VLSI 
                 Low cost 
                 plate to form the 
                 patent 
               
               
                 using 
                 deposition 
                 Existing 
                 nozzle chamber 
                 applications 
               
               
                 VLSI 
                 techniques. 
                 processes can be 
                 Surface may 
                 IJ01, IJ02, 
               
               
                 litho- 
                 Nozzles are etched 
                 used 
                 be fragile to the 
                 IJ04, IJ11, IJ12, 
               
               
                 graphic 
                 in the nozzle plate 
                   
                 touch 
                 IJ17, IJ18, IJ20, 
               
               
                 processes 
                 using VLSI 
                   
                   
                 IJ22, IJ24, IJ27, 
               
               
                   
                 lithography and 
                   
                   
                 IJ28, IJ29, IJ30, 
               
               
                   
                 etching. 
                   
                   
                 IJ31, IJ32, IJ33, 
               
               
                   
                   
                   
                   
                 IJ34, IJ36, IJ37, 
               
               
                   
                   
                   
                   
                 IJ38, IJ39, IJ40, 
               
               
                   
                   
                   
                   
                 IJ41, IJ42, IJ43, 
               
               
                   
                   
                   
                   
                 IJ44 
               
               
                 Monolithic, 
                 The nozzle plate is 
                 High accuracy 
                 Requires long 
                 IJ03, IJ05, 
               
               
                 etched 
                 a buried etch stop 
                 (&lt;1 μm) 
                 etch times 
                 IJ06, IJ07, IJ08, 
               
               
                 through 
                 in the wafer. 
                 Monolithic 
                 Requires a 
                 IJ09, IJ10, IJ13, 
               
               
                 substrate 
                 Nozzle chambers 
                 Low cost 
                 support wafer 
                 IJ14, IJ15, IJ16, 
               
               
                   
                 are etched in the 
                 No differential 
                   
                 IJ19, IJ21, IJ23, 
               
               
                   
                 front of the wafer, 
                 expansion 
                   
                 IJ25, IJ26 
               
               
                   
                 and the wafer is 
               
               
                   
                 thinned from the 
               
               
                   
                 back side. Nozzles 
               
               
                   
                 are then etched in 
               
               
                   
                 the etch stop layer. 
               
               
                 No nozzle 
                 Various methods 
                 No nozzles to 
                 Difficult to 
                 Ricoh 1995 
               
               
                 plate 
                 have been tried to 
                 become clogged 
                 control drop 
                 Sekiya et al U.S. Pat. No. 
               
               
                   
                 eliminate the 
                   
                 position 
                 5,412,413 
               
               
                   
                 nozzles entirely, to 
                   
                 accurately 
                 1993 
               
               
                   
                 prevent nozzle 
                   
                 Crosstalk 
                 Hadimioglu et al 
               
               
                   
                 clogging. These 
                   
                 problems 
                 EUP 550,192 
               
               
                   
                 include thermal 
                   
                   
                 1993 Elrod et 
               
               
                   
                 bubble 
                   
                   
                 al EUP 572,220 
               
               
                   
                 mechanisms and 
               
               
                   
                 acoustic lens 
               
               
                   
                 mechanisms 
               
               
                 Trough 
                 Each drop ejector 
                 Reduced 
                 Drop firing 
                 IJ35 
               
               
                   
                 has a trough 
                 manufacturing 
                 direction is 
               
               
                   
                 through which a 
                 complexity 
                 sensitive to 
               
               
                   
                 paddle moves. 
                 Monolithic 
                 wicking. 
               
               
                   
                 There is no nozzle 
               
               
                   
                 plate. 
               
               
                 Nozzle slit 
                 The elimination of 
                 No nozzles to 
                 Difficult to 
                 1989 Saito et 
               
               
                 instead of 
                 nozzle holes and 
                 become clogged 
                 control drop 
                 al U.S. Pat. No. 
               
               
                 individual 
                 replacement by a 
                   
                 position 
                 4,799,068 
               
               
                 nozzles 
                 slit encompassing 
                   
                 accurately 
               
               
                   
                 many actuator 
                   
                 Crosstalk 
               
               
                   
                 positions reduces 
                   
                 problems 
               
               
                   
                 nozzle clogging, 
               
               
                   
                 but increases 
               
               
                   
                 crosstalk due to 
               
               
                   
                 ink surface waves 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 DROP EJECTION DIRECTION 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Edge 
                 Ink flow is along 
                 Simple 
                 Nozzles 
                 Canon 
               
               
                 (‘edge 
                 the surface of the 
                 construction 
                 limited to edge 
                 Bubblejet 1979 
               
               
                 shooter’) 
                 chip, and ink drops 
                 No silicon 
                 High 
                 Endo et al GB 
               
               
                   
                 are ejected from 
                 etching required 
                 resolution is 
                 patent 2,007,162 
               
               
                   
                 the chip edge. 
                 Good heat 
                 difficult 
                 Xerox heater- 
               
               
                   
                   
                 sinking via 
                 Fast color 
                 in-pit 1990 
               
               
                   
                   
                 substrate 
                 printing requires 
                 Hawkins et al 
               
               
                   
                   
                 Mechanically 
                 one print head 
                 U.S. Pat. No. 4,899,181 
               
               
                   
                   
                 strong 
                 per color 
                 Tone-jet 
               
               
                   
                   
                 Ease of chip 
               
               
                   
                   
                 handing 
               
               
                 Surface 
                 Ink flow is along 
                 No bulk 
                 Maximum ink 
                 Hewlett- 
               
               
                 (‘roof 
                 the surface of the 
                 silicon etching 
                 flow is severely 
                 Packard TIJ 
               
               
                 shooter’) 
                 chip, and ink drops 
                 required 
                 restricted 
                 1982 Vaught et 
               
               
                   
                 are ejected from 
                 Silicon can 
                   
                 al U.S. Pat. No. 
               
               
                   
                 the chip surface, 
                 make an 
                   
                 4,490,728 
               
               
                   
                 normal to the 
                 effective heat 
                   
                 IJ02, IJ11, 
               
               
                   
                 plane of the chip. 
                 sink 
                   
                 IJ12, IJ20, IJ22 
               
               
                   
                   
                 Mechanical 
               
               
                   
                   
                 strength 
               
               
                 Through 
                 Ink flow is through 
                 High ink flow 
                 Requires bulk 
                 Silverbrook, 
               
               
                 chip, 
                 the chip, and ink 
                 Suitable for 
                 silicon etching 
                 EP 0771 658 A2 
               
               
                 forward 
                 drops are ejected 
                 pagewidth print 
                   
                 and related 
               
               
                 (‘up 
                 from the front 
                 heads 
                   
                 patent 
               
               
                 shooter’) 
                 surface of the chip. 
                 High nozzle 
                   
                 applications 
               
               
                   
                   
                 packing density 
                   
                 IJ04, IJ17, 
               
               
                   
                   
                 therefore low 
                   
                 IJ18, IJ24, IJ27-IJ45 
               
               
                   
                   
                 manufacturing 
               
               
                   
                   
                 cost 
               
               
                 Through 
                 Ink flow is through 
                 High ink flow 
                 Requires 
                 IJ01, IJ03, 
               
               
                 chip, 
                 the chip, and ink 
                 Suitable for 
                 wafer thinning 
                 IJ05, IJ06, IJ07, 
               
               
                 reverse 
                 drops are ejected 
                 pagewidth print 
                 Requires 
                 IJ08, IJ09, IJ10, 
               
               
                 (‘down 
                 from the rear 
                 heads 
                 special handling 
                 IJ13, IJ14, IJ15, 
               
               
                 shooter’) 
                 surface of the chip. 
                 High nozzle 
                 during 
                 IJ16, IJ19, IJ21, 
               
               
                   
                   
                 packing density 
                 manufacture 
                 IJ23, IJ25, IJ26 
               
               
                   
                   
                 therefore low 
               
               
                   
                   
                 manufacturing 
               
               
                   
                   
                 cost 
               
               
                 Through 
                 Ink flow is through 
                 Suitable for 
                 Pagewidth 
                 Epson Stylus 
               
               
                 actuator 
                 the actuator, which 
                 piezoelectric 
                 print heads 
                 Tektronix hot 
               
               
                   
                 is not fabricated as 
                 print heads 
                 require several 
                 melt 
               
               
                   
                 part of the same 
                   
                 thousand 
                 piezoelectric ink 
               
               
                   
                 substrate as the 
                   
                 connections to 
                 jets 
               
               
                   
                 drive transistors. 
                   
                 drive circuits 
               
               
                   
                   
                   
                 Cannot be 
               
               
                   
                   
                   
                 manufactured in 
               
               
                   
                   
                   
                 standard CMOS 
               
               
                   
                   
                   
                 fabs 
               
               
                   
                   
                   
                 Complex 
               
               
                   
                   
                   
                 assembly 
               
               
                   
                   
                   
                 required 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 INK TYPE 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Aqueous, 
                 Water based ink 
                 Environmentally 
                 Slow drying 
                 Most existing 
               
               
                 dye 
                 which typically 
                 friendly 
                 Corrosive 
                 ink jets 
               
               
                   
                 contains: water, 
                 No odor 
                 Bleeds on 
                 All IJ series 
               
               
                   
                 dye, surfactant, 
                   
                 paper 
                 ink jets 
               
               
                   
                 humectant, and 
                   
                 May 
                 Silverbrook, 
               
               
                   
                 biocide. 
                   
                 strikethrough 
                 EP 0771 658 A2 
               
               
                   
                 Modern ink dyes 
                   
                 Cockles paper 
                 and related 
               
               
                   
                 have high water- 
                   
                   
                 patent 
               
               
                   
                 fastness, light 
                   
                   
                 applications 
               
               
                   
                 fastness 
               
               
                 Aqueous, 
                 Water based ink 
                 Environmentally 
                 Slow drying 
                 IJ02, IJ04, 
               
               
                 pigment 
                 which typically 
                 friendly 
                 Corrosive 
                 IJ21, IJ26, IJ27, 
               
               
                   
                 contains: water, 
                 No odor 
                 Pigment may 
                 IJ30 
               
               
                   
                 pigment, 
                 Reduced bleed 
                 clog nozzles 
                 Silverbrook, 
               
               
                   
                 surfactant, 
                 Reduced 
                 Pigment may 
                 EP 0771 658 A2 
               
               
                   
                 humectant, and 
                 wicking 
                 clog actuator 
                 and related 
               
               
                   
                 biocide. 
                 Reduced 
                 mechanisms 
                 patent 
               
               
                   
                 Pigments have an 
                 strikethrough 
                 Cockles paper 
                 applications 
               
               
                   
                 advantage in 
                   
                   
                 Piezoelectric 
               
               
                   
                 reduced bleed, 
                   
                   
                 ink-jets 
               
               
                   
                 wicking and 
                   
                   
                 Thermal ink 
               
               
                   
                 strikethrough. 
                   
                   
                 jets (with 
               
               
                   
                   
                   
                   
                 significant 
               
               
                   
                   
                   
                   
                 restrictions) 
               
               
                 Methyl 
                 MEK is a highly 
                 Very fast 
                 Odorous 
                 All IJ series 
               
               
                 Ethyl 
                 volatile solvent 
                 drying 
                 Flammable 
                 ink jets 
               
               
                 Ketone 
                 used for industrial 
                 Prints on 
               
               
                 (MEK) 
                 printing on 
                 various 
               
               
                   
                 difficult surfaces 
                 substrates such 
               
               
                   
                 such as aluminum 
                 as metals and 
               
               
                   
                 cans. 
                 plastics 
               
               
                 Alcohol 
                 Alcohol based inks 
                 Fast drying 
                 Slight odor 
                 All IJ series 
               
               
                 (ethanol, 
                 can be used where 
                 Operates at 
                 Flammable 
                 ink jets 
               
               
                 2-butanol, 
                 the printer must 
                 sub-freezing 
               
               
                 and 
                 operate at 
                 temperatures 
               
               
                 others) 
                 temperatures 
                 Reduced 
               
               
                   
                 below the freezing 
                 paper cockle 
               
               
                   
                 point of water. An 
                 Low cost 
               
               
                   
                 example of this is 
               
               
                   
                 in-camera 
               
               
                   
                 consumer 
               
               
                   
                 photographic 
               
               
                   
                 printing. 
               
               
                 Phase 
                 The ink is solid at 
                 No drying 
                 High viscosity 
                 Tektronix hot 
               
               
                 change 
                 room temperature, 
                 time-ink 
                 Printed ink 
                 melt 
               
               
                 (hot melt) 
                 and is melted in 
                 instantly freezes 
                 typically has a 
                 piezoelectric ink 
               
               
                   
                 the print head 
                 on the print 
                 ‘waxy’ feel 
                 jets 
               
               
                   
                 before jetting. Hot 
                 medium 
                 Printed pages 
                 1989 Nowak 
               
               
                   
                 melt inks are 
                 Almost any 
                 may ‘block’ 
                 U.S. Pat. No. 4,820,346 
               
               
                   
                 usually wax based, 
                 print medium 
                 Ink 
                 All IJ series 
               
               
                   
                 with a melting 
                 can be used 
                 temperature may 
                 ink jets 
               
               
                   
                 point around 80° C. 
                 No paper 
                 be above the 
               
               
                   
                 After jetting 
                 cockle occurs 
                 curie point of 
               
               
                   
                 the ink freezes 
                 No wicking 
                 permanent 
               
               
                   
                 almost instantly 
                 occurs 
                 magnets 
               
               
                   
                 upon contacting 
                 No bleed 
                 Ink heaters 
               
               
                   
                 the print medium 
                 occurs 
                 consume power 
               
               
                   
                 or a transfer roller. 
                 No 
                 Long warm- 
               
               
                   
                   
                 strikethrough 
                 up time 
               
               
                   
                   
                 occurs 
               
               
                 Oil 
                 Oil based inks are 
                 High 
                 High 
                 All IJ series 
               
               
                   
                 extensively used in 
                 solubility 
                 viscosity: this is 
                 ink jets 
               
               
                   
                 offset printing. 
                 medium for 
                 a significant 
               
               
                   
                 They have 
                 some dyes 
                 limitation for use 
               
               
                   
                 advantages in 
                 Does not 
                 in ink jets, which 
               
               
                   
                 improved 
                 cockle paper 
                 usually require a 
               
               
                   
                 characteristics on 
                 Does not wick 
                 low viscosity. 
               
               
                   
                 paper (especially 
                 through paper 
                 Some short 
               
               
                   
                 no wicking or 
                   
                 chain and multi- 
               
               
                   
                 cockle). Oil 
                   
                 branched oils 
               
               
                   
                 soluble dies and 
                   
                 have a 
               
               
                   
                 pigments are 
                   
                 sufficiently low 
               
               
                   
                 required. 
                   
                 viscosity. 
               
               
                   
                   
                   
                 Slow drying 
               
               
                 Micro- 
                 A microemulsion 
                 Stops ink 
                 Viscosity 
                 All IJ series 
               
               
                 emulsion 
                 is a stable, self 
                 bleed 
                 higher than 
                 ink jets 
               
               
                   
                 forming emulsion 
                 High dye 
                 water 
               
               
                   
                 of oil, water, and 
                 solubility 
                 Cost is 
               
               
                   
                 surfactant. The 
                 Water, oil, 
                 slightly higher 
               
               
                   
                 characteristic drop 
                 and amphiphilic 
                 than water based 
               
               
                   
                 size is less than 
                 soluble dies can 
                 ink 
               
               
                   
                 100 nm, and is 
                 be used 
                 High 
               
               
                   
                 determined by the 
                 Can stabilize 
                 surfactant 
               
               
                   
                 preferred curvature 
                 pigment 
                 concentration 
               
               
                   
                 of the surfactant. 
                 suspensions 
                 required (around 
               
               
                   
                   
                   
                 5%)