Patent Publication Number: US-6340222-B1

Title: Utilizing venting in a MEMS liquid pumping system

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application serial numbers (U.S. Ser. No.) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority. 
     
       
         
           
               
               
               
             
               
                   
               
               
                 CROSS-REFERENCED 
                 U.S. PATENT/ 
                   
               
               
                 AUSTRALIAN 
                 PATENT APPLICATION 
               
               
                 PROVISIONAL 
                 (CLAIMING RIGHT OF 
               
               
                 PATENT 
                 PRIORITY FROM AUSTRALIAN 
                 DOCKET 
               
               
                 APPLICATION NO. 
                 PROVISIONAL APPLICATION) 
                 NO. 
               
               
                   
               
             
            
               
                 PO7991 
                 09/113,060 
                 ART01 
               
               
                 PO8505 
                 09/113,070 
                 ART02 
               
               
                 PO7988 
                 09/113,073 
                 ART03 
               
               
                 PO9395 
                 09/112,748 
                 ART04 
               
               
                 PO8017 
                 09/112,747 
                 ART06 
               
               
                 PO8014 
                 09/112,776 
                 ART07 
               
               
                 PO8025 
                 09/112,750 
                 ART08 
               
               
                 PO8032 
                 09/112,746 
                 ART09 
               
               
                 PO7999 
                 09/112,743 
                 ART10 
               
               
                 PO7998 
                 09/112,742 
                 ART11 
               
               
                 PO8031 
                 09/112,741 
                 ART12 
               
               
                 PO8030 
                 09/112,740 
                 ART13 
               
               
                 PO7997 
                 09/112,739 
                 ART15 
               
               
                 PO7979 
                 09/113,053 
                 ART16 
               
               
                 PO8015 
                 09/112,738 
                 ART17 
               
               
                 PO7978 
                 09/113,067 
                 ART18 
               
               
                 PO7982 
                 09/113,063 
                 ART19 
               
               
                 PO7989 
                 09/113,069 
                 ART20 
               
               
                 PO8019 
                 09/112,744 
                 ART21 
               
               
                 PO7980 
                 69/113,058 
                 ART22 
               
               
                 PO8018 
                 09/112,777 
                 ART24 
               
               
                 PO7938 
                 09/113,224 
                 ART25 
               
               
                 PO8016 
                 09/112,804 
                 ART26 
               
               
                 PO8024 
                 09/112,805 
                 ART27 
               
               
                 PO7940 
                 09/113,072 
                 ART28 
               
               
                 PO7939 
                 09/112,785 
                 ART29 
               
               
                 PO8501 
                 09/112,797 
                 ART30 
               
               
                 PO8500 
                 09/112,796 
                 ART31 
               
               
                 PO7987 
                 09/113,071 
                 ART32 
               
               
                 PO8022 
                 09/112,824 
                 ART33 
               
               
                 PO8497 
                 09/113,090 
                 ART34 
               
               
                 PO8020 
                 09/112,823 
                 ART38 
               
               
                 PO8023 
                 09/113,222 
                 ART39 
               
               
                 PO8504 
                 09/112,786 
                 ART42 
               
               
                 PO8000 
                 09/113,051 
                 ART43 
               
               
                 PO7977 
                 09/112,782 
                 ART44 
               
               
                 PO7934 
                 09/113,056 
                 ART45 
               
               
                 PO7990 
                 09/113,059 
                 ART46 
               
               
                 PO8499 
                 09/113,091 
                 ART47 
               
               
                 PO8502 
                 09/112,753 
                 ART48 
               
               
                 PO7981 
                 09/113,055 
                 ART50 
               
               
                 PO7986 
                 09/113,057 
                 ART51 
               
               
                 PO7983 
                 09/113,054 
                 ART52 
               
               
                 PO8026 
                 09/112,752 
                 ART53 
               
               
                 PO8027 
                 09/112,759 
                 ART54 
               
               
                 PO8028 
                 09/112,757 
                 ART56 
               
               
                 PO9394 
                 09/112,758 
                 ART57 
               
               
                 PO9396 
                 09/113,107 
                 ART58 
               
               
                 PO9397 
                 09/112,829 
                 ART59 
               
               
                 PO9398 
                 09/112,792 
                 ART60 
               
               
                 PO9399 
                 6,106,147 
                 ART61 
               
               
                 PO9400 
                 09/112,790 
                 ART62 
               
               
                 PO9401 
                 09/112,789 
                 ART63 
               
               
                 PO9402 
                 09/112,788 
                 ART64 
               
               
                 PO9403 
                 09/112,795 
                 ART65 
               
               
                 PO9405 
                 09/112,749 
                 ART66 
               
               
                 PP0959 
                 09/112,784 
                 ART68 
               
               
                 PP1397 
                 09/112,783 
                 ART69 
               
               
                 PP2370 
                 09/112,781 
                 DOT01 
               
               
                 PP2371 
                 09/113,052 
                 DOT02 
               
               
                 PO8003 
                 09/112,834 
                 Fluid01 
               
               
                 PO8005 
                 09/113,103 
                 Fluid02 
               
               
                 PO9404 
                 09/113,101 
                 Fluid03 
               
               
                 PO8066 
                 09/112,751 
                 IJ01 
               
               
                 PO8072 
                 09/112,787 
                 IJ02 
               
               
                 PO8040 
                 09/112,802 
                 IJ03 
               
               
                 PO8071 
                 09/112,803 
                 IJ04 
               
               
                 PO8047 
                 09/113,097 
                 IJ05 
               
               
                 PO8035 
                 09/113,099 
                 IJ06 
               
               
                 PO8044 
                 09/113,084 
                 IJ07 
               
               
                 PO8063 
                 09/113,066 
                 IJ08 
               
               
                 PO8057 
                 09/112,778 
                 IJ09 
               
               
                 PO8056 
                 09/112,779 
                 IJ10 
               
               
                 PO8069 
                 09/113,077 
                 IJ11 
               
               
                 PO8049 
                 09/113,061 
                 IJ12 
               
               
                 PO8036 
                 09/112,818 
                 IJ13 
               
               
                 PO8048 
                 09/112,816 
                 IJ14 
               
               
                 PO8070 
                 09/112,772 
                 IJ15 
               
               
                 PO8067 
                 09/112,819 
                 IJ16 
               
               
                 PO8001 
                 09/112,815 
                 IJ17 
               
               
                 PO8038 
                 09/113,096 
                 IJ18 
               
               
                 PO8033 
                 09/113,068 
                 IJ19 
               
               
                 PO8002 
                 09/113,095 
                 IJ20 
               
               
                 PO8068 
                 09/112,808 
                 IJ21 
               
               
                 PO8062 
                 09/112,809 
                 IJ22 
               
               
                 PO8034 
                 09/112,780 
                 IJ23 
               
               
                 PO8039 
                 09/113,083 
                 IJ24 
               
               
                 PO8041 
                 09/113,121 
                 IJ25 
               
               
                 PO8004 
                 09/113,122 
                 IJ26 
               
               
                 PO8037 
                 09/112,793 
                 IJ27 
               
               
                 PO8043 
                 09/112,794 
                 IJ28 
               
               
                 PO8042 
                 09/113,128 
                 IJ29 
               
               
                 PO8064 
                 09/113,127 
                 IJ30 
               
               
                 PO9389 
                 09/112,756 
                 IJ31 
               
               
                 PO9391 
                 09/112,755 
                 IJ32 
               
               
                 PP0888 
                 09/112,754 
                 IJ33 
               
               
                 PP0891 
                 09/112,811 
                 IJ34 
               
               
                 PP0890 
                 09/112,812 
                 IJ35 
               
               
                 PP0873 
                 09/112,813 
                 IJ36 
               
               
                 PP0993 
                 09/112,814 
                 IJ37 
               
               
                 PP0890 
                 09/112,764 
                 IJ38 
               
               
                 PP1398 
                 09/112,765 
                 IJ39 
               
               
                 PP2592 
                 09/112,767 
                 IJ40 
               
               
                 PP2593 
                 09/112,768 
                 IJ41 
               
               
                 PP3991 
                 09/112,807 
                 IJ42 
               
               
                 PP3987 
                 09/112,806 
                 IJ43 
               
               
                 PP3985 
                 09/112,820 
                 IJ44 
               
               
                 PP3983 
                 09/112,821 
                 IJ45 
               
               
                 PO7935 
                 09/112,822 
                 IJM01 
               
               
                 PO7936 
                 09/112,825 
                 IJM02 
               
               
                 PO7937 
                 09/112,826 
                 IJM03 
               
               
                 PO8061 
                 09/112,827 
                 IJM04 
               
               
                 PO8054 
                 09/112,828 
                 IJM05 
               
               
                 PO8065 
                 6,071,750 
                 IJM06 
               
               
                 PO8055 
                 09/113,108 
                 IJM07 
               
               
                 PO8053 
                 09/113,109 
                 IJM08 
               
               
                 PO8078 
                 09/113,123 
                 IJM09 
               
               
                 PO7933 
                 09/113,114 
                 IJM10 
               
               
                 PO7950 
                 09/113,115 
                 IJM11 
               
               
                 PO7949 
                 09/113,129 
                 IJM12 
               
               
                 PO8060 
                 09/113,124 
                 IJM13 
               
               
                 PO8059 
                 09/113,125 
                 IJM14 
               
               
                 PO8073 
                 09/113,126 
                 IJM15 
               
               
                 PO8076 
                 09/113,119 
                 IJM16 
               
               
                 PO8075 
                 09/113,120 
                 IJM17 
               
               
                 PO8079 
                 09/113,221 
                 IJM18 
               
               
                 PO8050 
                 09/113,116 
                 IJM19 
               
               
                 PO8052 
                 09/113,118 
                 IJM20 
               
               
                 PO7948 
                 09/113,117 
                 IJM21 
               
               
                 PO7951 
                 09/113,113 
                 IJM22 
               
               
                 PO8074 
                 09/113,130 
                 IJM23 
               
               
                 PO7941 
                 09/113,110 
                 IJM24 
               
               
                 PO8077 
                 09/113,112 
                 IJM25 
               
               
                 PO8058 
                 09/113,087 
                 IJM26 
               
               
                 PO8051 
                 09/113,074 
                 IJM27 
               
               
                 PO8045 
                 6,111,754 
                 IJM28 
               
               
                 PO7952 
                 09/113,088 
                 IJM29 
               
               
                 PO8046 
                 09/112,771 
                 IJM30 
               
               
                 PO9390 
                 09/112,769 
                 IJM31 
               
               
                 PO9392 
                 09/112,770 
                 IJM32 
               
               
                 PP0889 
                 09/112,798 
                 IJM35 
               
               
                 PP0887 
                 09/112,801 
                 IJM36 
               
               
                 PP0882 
                 09/112,800 
                 IJM37 
               
               
                 PP0874 
                 09/112,799 
                 IJM38 
               
               
                 PP1396 
                 09/113,098 
                 IJM39 
               
               
                 PP3989 
                 09/112,833 
                 IJM40 
               
               
                 PP2591 
                 09/112,832 
                 1JM41 
               
               
                 PP3990 
                 09/112,831 
                 IJM42 
               
               
                 PP3986 
                 09/112,830 
                 IJM43 
               
               
                 PP3984 
                 09/112,836 
                 IJM44 
               
               
                 PP3982 
                 09/112,835 
                 IJM45 
               
               
                 PP0895 
                 09/113,102 
                 IR01 
               
               
                 PP0870 
                 09/113,106 
                 IR02 
               
               
                 PP0869 
                 09/113,105 
                 IR04 
               
               
                 PP0887 
                 09/113,104 
                 IR05 
               
               
                 PP0885 
                 09/112,810 
                 IR06 
               
               
                 PP0884 
                 09/112,766 
                 IR10 
               
               
                 PP0886 
                 09/113,085 
                 IR12 
               
               
                 PP0871 
                 09/113,086 
                 IR13 
               
               
                 PP0876 
                 09/113,094 
                 IR14 
               
               
                 PP0877 
                 09/112,760 
                 IR16 
               
               
                 PP0878 
                 09/112,773 
                 IR17 
               
               
                 PP0879 
                 09/112,774 
                 IR18 
               
               
                 PP0883 
                 09/112,775 
                 IR19 
               
               
                 PP0880 
                 6,152,619 
                 IR20 
               
               
                 PP0881 
                 09/113,092 
                 IR21 
               
               
                 PO8006 
                 6,087,638 
                 MEMS02 
               
               
                 PO8007 
                 09/113,093 
                 MEMS03 
               
               
                 PO8008 
                 09/113,062 
                 MEMS04 
               
               
                 PO8010 
                 6,041,600 
                 MEMS05 
               
               
                 PO8011 
                 09/113,082 
                 MEMS06 
               
               
                 PO7947 
                 6,067,797 
                 MEMS07 
               
               
                 PO7944 
                 09/113,080 
                 MEMS09 
               
               
                 PO7946 
                 6,044,646 
                 MEMS10 
               
               
                 PO9393 
                 09/113,065 
                 MEMS11 
               
               
                 PP0875 
                 09/113,078 
                 MEMS12 
               
               
                 PP0894 
                 09/113,075 
                 MEMS13 
               
               
                   
               
            
           
         
       
     
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The present invention relates to the venting of an ink jet nozzle. 
     BACKGROUND OF THE INVENTION 
     Recently, micro-electro mechanical systems (MEMS) have become increasingly popular. One use of such a system is in the ejection of ink in an ink jet printing device. It is important in such devices to have efficient operation. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an efficient operation of an ink jet nozzle when constructed on a MEMS scale. 
     In accordance with a first aspect of the present invention there is provided a micro-mechanical nozzle having thermal actuator which includes a hydrophobic surface surrounded by other hydrophobic surfaces. A method of reducing the operation energy requirements of said actuator comprises the step of providing an air inlet in fluid communication with said hydrophobic surface. The air inlet allow the flow of air into and out of a volume adjacent said hydrophobic surface. Further, the air inlet is surrounded by hydrophobic material and includes a plurality of small spaced apart holes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Notwithstanding any other forms which 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 of a single ink jet nozzle incorporating a venting arrangement constructed in accordance with the preferred embodiment. 
     FIG. 2 is a schematic cross-sectional view of the single ink jet nozzle with a thermal actuator of the nozzle in its activated state. 
     FIG. 3 is a schematic diagram of a conductive layer utilized in the thermal actuator of the ink jet nozzle. 
     FIG. 4 is a close-up perspective view of portion A of FIG.  3 . 
     FIG. 5 is a cross-sectional schematic diagram illustrating the construction of the conductive layer of FIG.  3 . 
     FIG. 6 is a schematic cross-sectional diagram illustrating the development of a resist material through a half-toned mask utilized in the fabrication of the conductive layer of FIG.  3 . 
     FIG. 7 is an exploded perspective view of the ink jet nozzle of FIG.  1 . 
     FIG. 8 is a perspective view of a section of an ink jet printhead incorporating a plurality of the ink jet nozzles of FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS 
     The preferred embodiment of the present invention will be discussed with reference to an ink jet nozzle wherein it is required to provide energy efficient operation of an ink jet printing device incorporating a plurality of the ink jet nozzles. The present invention should however, not be restricted to the field of ink jet printing devices. 
     In the preferred embodiment, the ink jet nozzle from which ink is ejected is actuated by means of a thermal actuator which includes a “corrugated” copper heating element encased in a polytetrafluoroethylene (PTFE) layer. Those of ordinary skill in the field will appreciate that PTFE is inherently hydrophobic. 
     Turning now to FIG. 1, there is illustrated a cross-sectional view of a single ink jet nozzle  10  in accordance with the present embodiment. The ink jet nozzle  10  includes an ink ejection port  11  for the ejection of ink from a chamber  12  by means of actuation of a thermal paddle actuator  13 . The thermal paddle actuator  13  comprises an inner copper heating portion  14  and paddle  15  which are encased in a PTFE layer  16 . The PTFE layer  16  has an extremely high coefficient of thermal expansion (approximately 770×10−6, or around 380 times that of silicon). The PTFE layer  16  is also highly hydrophobic which results in an air bubble  17  being formed under the actuator  13  due to out-gassing etc. A top surface of the PTFE layer  16  is treated so as to make it hydrophilic. The heating portion  14  is also formed within a lower portion of the actuator  13 . 
     The heating portion  14  is connected at ends  20 , 21  (see also FIG. 7) to a lower CMOS drive layer  18  containing drive circuitry (not shown). For the purposes of actuation of the actuator  13 , a current is passed through the heating portion  14  which heats the lower portion of the actuator  13 . Turning now to FIG. 2, a bottom surface of the actuator  13 , in contact with an air bubble  17  remains heated while any top surface heating is carried away by the exposure of the top surface of the actuator  13  to the ink within the chamber  12 . Hence, the lower portion of the PTFE layer expands more rapidly resulting in a general bending upwards of the actuator  13  (as illustrated in FIG. 2) which consequentially causes the ejection of ink from the ink ejection port  11 . An air inlet channel  28  is formed between a nitride layer  42 , and a PTFE layer  26  such that air is free to flow in the direction of an arrow  29  along a channel  28  and through holes  25 , to accommodate any fluctuating pressure influences plurality of posts  27  are positioned between the layers  42 ,  26 . As can be seen in FIGS. 1 and 2, air introduced into the ink jet nozzle  10  is in fluid communication with the air bubble  17 . Thus the air flow acts to reduce a vacuum acting on the bottom surface of the actuator  13  during operation. As a result, less energy is required for the movement of the actuator  13 . 
     The actuator  13  can be deactivated by turning off the current to the heating portion  14 . This results in a return of the actuator  13  to its rest position. 
     The actuator  13  includes a number of significant features. In FIG. 3 there is illustrated a schematic diagram of the conductive layer of the thermal actuator  13 . The conductive layer includes the panel  15 , which can be constructed from the same material as the heating portion as  14 , i.e. copper, and which contains a series of holes  23 . The holes  23  are provided for interconnecting PTFE both above and below the panel  15  so as to resist any movement of the PTFE layers past the panel  15  and thereby reduce any opportunities for the delamination of the PTFE and the copper. 
     Turning to FIG. 4, there is illustrated a close up view of a portion of the actuator  13  of FIG. 1 illustrating corrugations  22  of the heating portion  14 . The corrugations  22  of the heater  14  allow for a rapid heating of the lower portion. Any resistive heater which is based upon applying a current to heat an object will result in a rapid, substantially uniform elevation in temperature of the outer surface of the current carrying conductor. The surrounding PTFE is therefore heated by means of thermal conduction from the resistive element. This thermal conduction is known to proceed, to a first approximation, at a substantially linear rate with respect to distance from a resistive element. By utilizing a corrugated resistive element, the lower portion of the actuator  13  is more rapidly heated. Therefore, the utilization of a corrugated resistive element results in a more rapid heating of the lower portion and therefore a rapid actuation of the actuator  13 . Further the corrugations  22  also assist in resisting any delamination of the copper and PTFE. 
     Turning now to FIG. 5, the corrugations  22  can be formed by depositing a resist layer  50  on top of the first PTFE layer  51 . The resist layer  50  is exposed utilizing a mask  52  having a half-tone pattern delineating the corrugations. After development, the resist layer  50  contains the corrugation pattern. The resist layer  50  and the PTFE layer  51  are then etched utilizing an etchant that erodes the resist layer  50  at substantially the same rate as the PTFE layer  51 . This transfers the corrugated pattern into the PTFE layer  51 . Turning to FIG. 6, on top of the corrugated PTFE layer  51  is deposited the heating portion  14  which takes on a corrugated form in accordance with its under layer. The copper heating portion  14  is then etched in a serpentine or concertina form. Subsequently, a second PTFE layer  53  is deposited on top of the heating portion  14  so as to form a top layer of the thermal actuator  13 . Finally, the second PTFE layer  52  is planarized to form the top surface of the thermal actuator  13  (FIG.  1 ). 
     Returning again now to FIG. 1, it is noted that ink can be supplied via a channel  38  which can be constructed by means of deep anisotropic silicon trench etching such as that available from STS Limited (“Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology). The ink supply flows from the channel  38  through side grill portions  40  (see also FIG. 7) into the chamber  12 . Importantly, the grill portions  40  which can comprise silicon nitride or similar insulating material act to remove foreign bodies from the ink flow. The grill  40  also helps to pinch the PTFE actuator  13  to a base CMOS layer  18 , the pinching providing an important assistance for the thermal actuator  13  so as to ensure a substantially decreased likelihood of the thermal actuator layer  13  separating from a base CMOS layer  18 . 
     A series of sacrificial etchant holes  19 , are provided in a top wall  48  of the chamber  12  to allow sacrificial etchant to enter the chamber  12  during fabrication so as to increase the rate of etching. The small size of the holes  19 , does not affect the operation of the device  10  substantially as the surface tension across the holes  19 , stops ink from being ejected from these holes, whereas, the larger size port  11  allows for the ejection of ink. 
     Turning now to FIG. 7, there is illustrated an exploded perspective view of a single nozzle  10 . The nozzle  10  can be formed in layers starting with a silicon wafer device  41  having a CMOS layer  18  on top thereof as required. The CMOS layer  18  provides the various drive circuitry for driving the copper heating portion  14 . 
     On top of the CMOS layer  18  a nitride layer  42  is deposited, providing protection for lower layers from corrosion or etching. Next, a PTFE layer  26  is constructed having the aforementioned holes  25 , and posts  27 . The structure of the PTFE layer  26  can be formed by first laying down a sacrificial glass layer (not shown) onto which the PTFE layer  26  is deposited. The PTFE layer  26  includes various features, for example, a lower ridge portion  30  in addition to vias for subsequent material layers. 
     In construction of the actuator  13  (FIG.  1 ), the process of creating a first PTFE layer proceeds by laying down a sacrificial layer on top of layer  26  in which the air bubble underneath actuator  13  (FIG. 1) subsequently forms. On top of this is formed a first PTFE layer utilizing the relevant mask. Preferably, the PTFE layer includes vias for the subsequent copper interconnections. Next, a copper layer  43  is deposited on top of the first PTFE layer and a second PTFE layer is deposited on top of the copper layer  43 , in each case, utilizing the required mask. 
     The nitride layer  46  can be formed by the utilization of a sacrificial glass layer which is masked and etched as required to form the side walls and the grill  40 . Subsequently, the top nitride layer  48  is deposited again utilizing the appropriate mask having the holes  19  as required. Subsequently, the various sacrificial layers can be etched away so as to release the structure of the thermal actuator  13 . 
     In FIG. 8 there is illustrated a section of an ink jet printhead configuration  90  utilizing ink jet nozzles constructed in accordance with the preferred embodiment, e.g.  91 . The configuration  90  can be utilized in a three color process 1600 dpi print-head utilizing 3 sets of 2 rows of nozzle chambers  92 , 93 , which are interconnected to one ink supply channel, e.g.  94 , for each set. The 3 supply channels  94 ,  95 ,  96  are interconnected to cyan coloured, magenta coloured and yellow coloured ink reservoirs respectively. 
     It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is, 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. However presently popular ink jet printing technologies are unlikely to be suitable. 
     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. 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 ink jet 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 which match 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, a 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. 
     
       
         
           
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) 
               
            
           
           
               
               
               
               
               
            
               
                 Thermal bubble 
                 An electrothermal heater heats 
                 Large force generated 
                 High power 
                 Canon Bubblejet 1979 Endo et 
               
               
                   
                 the ink to above boiling point, 
                 Simple construction 
                 Ink carrier limited to water 
                 al GB patent 2,0007,162 
               
               
                   
                 transferring significant heat to 
                 No moving parts 
                 Low efficiency 
                 Xerox heater-in-pit 1990 
               
               
                   
                 the aqueous ink. A bubble 
                 Fast operation 
                 High temperatures required 
                 Hawkins et al U.S. Pat. No. 
               
               
                   
                 nucleates and quickly forms, 
                 Small chip area required for 
                 High mechanical stress 
                 4,899,181 
               
               
                   
                 expelling the ink. The efficiency 
                 actuator 
                 Unusual materials required 
                 Hewlett-Packard TIJ 1982 
               
               
                   
                 of the process is low, with 
                   
                 Large drive transistors 
                 Vaught et al U.S. Pat. No. 
               
               
                   
                 typically less than 0.05% of the 
                   
                 Cavitation causes actuator 
                 4,490,728 
               
               
                   
                 electrical energy being trans- 
                   
                 failure 
               
               
                   
                 formed into kinetic energy of the 
                   
                 Kogation reduces bubble 
               
               
                   
                 drop. 
                   
                 formation 
               
               
                   
                   
                   
                 Large print heads are difficult to 
               
               
                   
                   
                   
                 fabricate 
               
               
                 Piezoelectric 
                 A piezoelectric crystal such as 
                 Low power consumption 
                 Very large area required for 
                 Kyser et al U.S. Pat. No. 
               
               
                   
                 lead lanthanum zirconate (PZT) 
                 Many ink types can be used 
                 actuator 
                 3,946,398 
               
               
                   
                 is electrically activated, and 
                 Fast operation 
                 Difficult to integrate with 
                 Zoltan U.S. Pat. No. 3,683,212 
               
               
                   
                 either expands, shears, or bends 
                 High efficiency 
                 electronics 
                 1973 Stemme U.S. Pat. No. 
               
               
                   
                 to apply pressure to the ink, 
                   
                 High voltage drive transistors 
                 3,747,120 
               
               
                   
                 ejecting drops. 
                   
                 required 
                 Epson Stylus 
               
               
                   
                   
                   
                 Full pagewidth print heads 
                 Tektronix 
               
               
                   
                   
                   
                 impractical due to actuator size 
                 IJ04 
               
               
                   
                   
                   
                 Requires electrical poling in 
               
               
                   
                   
                   
                 high field strengths during 
               
               
                   
                   
                   
                 manufacture 
               
               
                 Electrostrictive 
                 An electric field is used to 
                 Low power consumption 
                 Low maximum strain (approx. 
                 Seiko Epson, Usui et all JP 
               
               
                   
                 activate electrostriction in 
                 Many ink types can be used 
                 0.01%) 
                 253401/96 
               
               
                   
                 relaxor materials such as lead 
                 Low thermal expansion 
                 Large area required for actuator 
                 IJ04 
               
               
                   
                 lanthanum zirconate titanate 
                 Electric field strength 
                 due to low strain 
               
               
                   
                 (PLZT) or lead magnesium 
                 required (approx. 3.5 V/μm) 
                 Response speed is marginal 
               
               
                   
                 niobate (PMN). 
                 can be generated without 
                 (˜10 μs) 
               
               
                   
                   
                 difficulty 
                 High voltage drive transistors 
               
               
                   
                   
                 Does not require electrical 
                 required 
               
               
                   
                   
                 poling 
                 Full pagewidth print heads 
               
               
                   
                   
                   
                 impractical due to actuator size 
               
               
                 Ferroelectric 
                 An electric field is used to 
                 Low power consumption 
                 Difficult to integrate with 
                 IJ04 
               
               
                   
                 induce a phase transition 
                 Many ink types can be used 
                 electronics 
               
               
                   
                 between the antiferroelectric 
                 Fast operation (&lt;1 μs) 
                 Unusual materials such as 
               
               
                   
                 (AFE) and ferroelectric (FE) 
                 Relatively high longitudinal 
                 PLZSnT are required 
               
               
                   
                 phase. Perovskite materials such 
                 strain 
                 Actuators require a large area 
               
               
                   
                 as tin modified lead lanthanum 
                 High efficiency 
               
               
                   
                 zirconate titanate (PLZSnT) 
                 Electric field strength of around 
               
               
                   
                 exhibit large strains of up to 1% 
                 3 V/μm can be readily provided 
               
               
                   
                 associated with the AFE to FE 
               
               
                   
                 phase transition. 
               
               
                 Electrostatic 
                 Conductive plates are separated 
                 Low power consumption 
                 Difficult to operate electrostatic 
                 IJ02, IJ04 
               
               
                 plates 
                 by a compressible or fluid 
                 Many ink types can be used 
                 devices in an aqueous environ- 
               
               
                   
                 dielectric (usually air). Upon 
                 Fast operation 
                 ment 
               
               
                   
                 application of a voltage, the 
                   
                 The electrostatic actuator will 
               
               
                   
                 plates attract each other and 
                   
                 normally need to be separated 
               
               
                   
                 displace ink, causing drop 
                   
                 from the ink 
               
               
                   
                 ejection. The conductive plates 
                   
                 Very large area required to 
               
               
                   
                 may be in a comb or honeycomb 
                   
                 achieve high forces 
               
               
                   
                 structure, or stacked to increase 
                   
                 High voltage drive transistors 
               
               
                   
                 the surface area and therefore 
                   
                 may be required 
               
               
                   
                 the force. 
                   
                 Full pagewidth print heads are 
               
               
                   
                   
                   
                 not competitive due to actuator 
               
               
                   
                   
                   
                 size 
               
               
                 Electrostatic 
                 A strong electric field is applied 
                 Low current consumption 
                 High voltage required 
                 1989 Saito et al, U.S. Pat. No. 
               
               
                 pull on ink 
                 to the ink, whereupon electro- 
                 Low temperature 
                 May be damaged by sparks due 
                 4,799,068 
               
               
                   
                 static attraction accelerates the 
                   
                 to air breakdown 
                 1989 Miura et al, U.S. Pat. No. 
               
               
                   
                 ink towards the print medium. 
                   
                 Required field strength increases 
                 4,810,954 
               
               
                   
                   
                   
                 as the drop size decreases 
                 Tone-jet 
               
               
                   
                   
                   
                 High voltage drive transistors 
               
               
                   
                   
                   
                 required 
               
               
                   
                   
                   
                 Electrostatic field attracts dust 
               
               
                 Permanent 
                 An electromagnet directly 
                 Low power consumption 
                 Complex fabrication 
                 IJ07, IJ10 
               
               
                 magnet electro- 
                 attracts a permanent magnet, 
                 Many ink types can be used 
                 Permanent magnetic material 
               
               
                 magnetic 
                 displacing ink and causing drop 
                 Fast operation 
                 such as Neodymium Iron Boron 
               
               
                   
                 ejection. Rare earth magnets 
                 High efficiency 
                 (NdFeB) required. 
               
               
                   
                 with a field strength around 1 
                 Easy extension from single 
                 High local currents required 
               
               
                   
                 Tesla can be used. Examples 
                 nozzles to pagewidth print 
                 Copper metalization should be 
               
               
                   
                 are: Samarium Cobalt (SaCo) 
                 heads 
                 used for long electromigration 
               
               
                   
                 and magnetic materials in the 
                   
                 lifetime and low resistivity 
               
               
                   
                 neodymium iron boron family 
                   
                 Pigmented inks are usually 
               
               
                   
                 (NdFeB, NdDyFeBNb, 
                   
                 infeasible 
               
               
                   
                 NdDyFeB, etc) 
                   
                 Operating temperature limited 
               
               
                   
                   
                   
                 to the Curie temperature (around 
               
               
                   
                   
                   
                 540 K.) 
               
               
                 Soft magnetic 
                 A solenoid induced a magnetic 
                 Low power consumption 
                 Complex fabrication 
                 IJ01, IJ05, IJ08, IJ10, IJ12, IJ14, 
               
               
                 core electro- 
                 field in a soft magnetic core or 
                 Many ink types can be used 
                 Materials not usually present in 
                 IJ15, IJ17 
               
               
                 magnetic 
                 yoke fabricated from a ferrous 
                 Fast operation 
                 a CMOS fab such as NiFe, 
               
               
                   
                 material such as electroplated 
                 High efficiency 
                 CoNiFe, or CoFe are required 
               
               
                   
                 iron alloys such as CoNiFe [1], 
                 Easy extension from single 
                 High local currents required 
               
               
                   
                 CoFe, or NiFe alloys. Typically, 
                 nozzles to pagewidth print 
                 Copper metalization should be 
               
               
                   
                 the soft magnetic material is in 
                 heads 
                 used for long electromigration 
               
               
                   
                 two parts, which are normally 
                   
                 lifetime and low resistivity 
               
               
                   
                 held apart by a spring. When the 
                   
                 Electroplating is required 
               
               
                   
                 solenoid is actuated, the two 
                   
                 High saturation flux density is 
               
               
                   
                 parts attract, displacing the ink. 
                   
                 required (2.0-2.1 T is 
               
               
                   
                   
                   
                 achievable with CoNiFe [1]) 
               
               
                 Lorenz force 
                 The Lorenz force acting on a 
                 Low power consumption 
                 Force acts as a twisting motion 
                 IJ06, IJ11, IJ13, IJ16 
               
               
                   
                 current carrying wire in a 
                 Many ink types can be used 
                 Typically, only a quarter of the 
               
               
                   
                 magnetic field is utilized. This 
                 Fast operation 
                 solenoid length provides force 
               
               
                   
                 allows the magnetic field to be 
                 High efficiency 
                 in a useful direction 
               
               
                   
                 supplied externally to the print 
                 Easy extension from single 
                 High local currents required 
               
               
                   
                 head, for example with rare 
                 nozzles to pagewidth print 
                 Copper metalization should be 
               
               
                   
                 earth permanent magnets. Only 
                 heads 
                 used for long electromigration 
               
               
                   
                 the current carrying wire need be 
                   
                 lifetime and low resistivity 
               
               
                   
                 fabricated on the print-head, 
                   
                 Pigmented inks are usually 
               
               
                   
                 simplifying materials require- 
                   
                 infeasible 
               
               
                   
                 ments. 
               
               
                 Magneto- 
                 The actuator uses the giant 
                 Many ink types can be used 
                 Force acts as a twisting motion 
                 Fischenbeck, U.S. Pat. No. 
               
               
                 striction 
                 magnetostrictive effect of 
                 Fast operation 
                 Unusual materials such as 
                 4,032,929 
               
               
                   
                 materials such as Terfenol-D (an 
                 Easy extension from single 
                 Terfenol-D are required 
                 IJ25 
               
               
                   
                 alloy of terbium, dysprosium 
                 nozzles to pagewidth print 
                 High local currents required 
               
               
                   
                 and iron developed at the Naval 
                 heads 
                 Copper metalization should be 
               
               
                   
                 Ordnance Laboratory, hence 
                 High force is available 
                 used for long electromigration 
               
               
                   
                 Ter-Fe-NOL). For efficiency, 
                   
                 lifetime and low resistivity 
               
               
                   
                 the actuator should be pre- 
                   
                 Pre-stressing may be required 
               
               
                   
                 stressed to approx. 8 MPa. 
               
               
                 Surface tension 
                 Ink under positive pressure is 
                 Low power consumption 
                 Requires supplementary force 
                 Silverbrook, EP 0771 658 A2 
               
               
                 reduction 
                 held in a nozzle by surface 
                 Simple construction 
                 to effect drop separation 
                 and related patent applications 
               
               
                   
                 tension. The surface tension of 
                 No unusual materials required in 
                 Requires special ink surfactants 
               
               
                   
                 the ink is reduced below the 
                 fabrication 
                 Speed may be limited by 
               
               
                   
                 bubble threshold, causing the ink 
                 High efficiency 
                 surfactant properties 
               
               
                   
                 to egress from the nozzle. 
                 Easy extension from single 
               
               
                   
                   
                 nozzles to pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 Viscosity 
                 The ink viscosity is locally 
                 Simple construction 
                 Requires supplementary force 
                 Silverbrook, EP 0771 658 A2 
               
               
                 reduction 
                 reduced to select which drops 
                 No unusual materials required in 
                 to effect drop separation 
                 and related patent applications 
               
               
                   
                 are to be ejected. A viscosity 
                 fabrication 
                 Requires special ink viscosity 
               
               
                   
                 reduction can be achieved 
                 Easy extension from single 
                 surfactants 
               
               
                   
                 electrothermally with most inks, 
                 nozzles to pagewidth print 
                 High speed is difficult to 
               
               
                   
                 but special inks can be 
                 heads 
                 achieve 
               
               
                   
                 engineered for a 100:1 viscosity 
                   
                 Requires oscillating ink pressure 
               
               
                   
                 reduction. 
                   
                 A high temperature difference 
               
               
                   
                   
                   
                 (typically 80 degrees) is required 
               
               
                 Acoustic 
                 An acoustic wave is generated 
                 Can operate without a nozzle 
                 Complex drive circuitry 
                 1993 Hadimioglu et al, EUP 
               
               
                   
                 and focussed upon the drop 
                 plate 
                 Complex fabrication 
                 550,192 
               
               
                   
                 ejection region. 
                   
                 Low efficiency 
                 1993 Elrod et al, EUP 572,220 
               
               
                   
                   
                   
                 Poor control of drop position 
               
               
                   
                   
                   
                 Poor control of drop volume 
               
               
                 Thermoelastic 
                 An actuator which relies upon 
                 Low power consumption 
                 Efficient aqueous operation 
                 IJ03, IJ09, IJ17, IJ18, IJ19, IJ20, 
               
               
                 bend actuator 
                 differential thermal expansion 
                 Many ink types can be used 
                 requires a thermal insulator 
                 IJ21, IJ22, IJ23, IJ24, IJ27, IJ28, 
               
               
                   
                 upon Joule heating is used. 
                 Simple planar fabrication 
                 on the hot side 
                 IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, 
               
               
                   
                   
                 Small chip area required for 
                 Corrosion prevention can be 
                 IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, 
               
               
                   
                   
                 actuator 
                 difficult 
                 IJ41 
               
               
                   
                   
                 Fast operation 
                 Pigmented inks may be 
               
               
                   
                   
                 High efficiency 
                 infeasible, as pigment particles 
               
               
                   
                   
                 CMOS compatible voltages and 
                 may jam the bend actuator 
               
               
                   
                   
                 currents 
               
               
                   
                   
                 Standard MEMS processes can 
               
               
                   
                   
                 be used 
               
               
                   
                   
                 Easy extension from single 
               
               
                   
                   
                 nozzles to pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 High CTE 
                 A material with a very high 
                 High force can be generated 
                 Requires special material (e.g. 
                 IJ09, IJ17, IJ18, IJ20, IJ21, IJ22, 
               
               
                 thermoelastic 
                 coefficient of thermal expansion 
                 Three methods of PTFE deposi- 
                 PTFE) 
                 IJ23, IJ24, IJ27, IJ28, IJ29, IJ30, 
               
               
                 actuator 
                 (CTE) such as polytetrafluoro- 
                 tion are under development: 
                 Requires a PTFE deposition 
                 IJ31, IJ42, IJ43, IJ44 
               
               
                   
                 ethylene (PTFE) is used. As 
                 chemical vapor deposition 
                 process, which is not yet 
               
               
                   
                 high CTE materials are usually 
                 (CVD), spin coating, and 
                 standard in ULSI fabs 
               
               
                   
                 non-conductive, a heater fabri- 
                 evaporation 
                 PTFE deposition cannot be 
               
               
                   
                 cation from a conductive 
                 PTFE is a candidate for low 
                 followed with high temper- 
               
               
                   
                 material is incorporated. A 
                 dielectric constant insula- 
                 ature (above 350° C.) 
               
               
                   
                 50 μm long PTFE bend actuator 
                 tion in ULSI 
                 processing 
               
               
                   
                 with polysilicon heater and 
                 Very low power consumption 
                 Pigmented inks may be 
               
               
                   
                 15 mW power input can provide 
                 Many ink types can be used 
                 infeasible, as pigment particles 
               
               
                   
                 180 μN force and 10 μm 
                 Simple planar fabrication 
                 may jam the bend actuator 
               
               
                   
                 deflection. Actuator motions 
                 Small chip area required for 
               
               
                   
                 include: 
                 actuator 
               
               
                   
                 Bend 
                 Fast operation 
               
               
                   
                 Push 
                 High efficiency 
               
               
                   
                 Buckle 
                 CMOS compatible voltages and 
               
               
                   
                 Rotate 
                 currents 
               
               
                   
                   
                 Easy extension from single 
               
               
                   
                   
                 nozzles to pagewidth print 
               
               
                   
                   
                 heads 
               
               
                 Conductive 
                 A polymer with a high co- 
                 High force can be generated 
                 Requires special materials 
                 IJ24 
               
               
                 polymer 
                 efficient of thermal expansion 
                 Very low power consumption 
                 development (High CTE con- 
               
               
                 thermoelastic 
                 (such as PTFE) is doped with 
                 Many ink types can be used 
                 ductive polymer) 
               
               
                   
                 conducting substances to 
                 Simple planar fabrication 
                 Requires a PTFE deposition 
               
               
                   
                 increase its conductivity to about 
                 Small chip area required for 
                 process, which is not yet 
               
               
                   
                 3 orders of magnitude below that 
                 actuator 
                 standard in ULSI fabs 
               
               
                   
                 of copper. The conducting 
                 Fast operation 
                 PTFE deposition cannot be 
               
               
                   
                 polymer expands when 
                 High efficiency 
                 followed with high temper- 
               
               
                   
                 resistively heated. Examples of 
                 CMOS compatible voltages and 
                 ature (above 350° C.) 
               
               
                   
                 conducting dopants include: 
                 currents 
                 processing 
               
               
                   
                 Carbon nanotubes 
                 Easy extension from single 
                 Evaporation and CVD deposi- 
               
               
                   
                 Metal fibers 
                 nozzles to pagewidth print 
                 tion techniques cannot be used 
               
               
                   
                 Conductive polymers such as 
                 heads 
                 Pigmented inks may be in- 
               
               
                   
                 doped polythiophene 
                   
                 feasible, as pigment particles 
               
               
                   
                 Carbon granules 
                   
                 may jam the bend actuator 
               
               
                 Shape memory 
                 A shape memory alloy such as 
                 High force is available 
                 Fatigue limits maximum number 
                 IJ26 
               
               
                 alloy 
                 TiNi (also known as Nitinol - 
                 (stresses of hundreds of 
                 of cycles 
               
               
                   
                 Nickel Titanium alloy developed 
                 MPa) 
                 Low strain (1%) is required to 
               
               
                   
                 at the Naval Ordnance Labora- 
                 Large strain is available 
                 extend fatigue resistance 
               
               
                   
                 tory) is thermally switched 
                 (more than 3%) 
                 Cycle rate limited by heat 
               
               
                   
                 between its weak martensitic 
                 High corrosion resistance 
                 removal 
               
               
                   
                 state and its high stiffness 
                 Simple construction 
                 Requires unusual materials 
               
               
                   
                 austenic state. The shape of the 
                 Easy extension from single 
                 (TiNi) 
               
               
                   
                 actuator in its martensitic state is 
                 nozzles to pagewidth print 
                 The latent heat of trans- 
               
               
                   
                 deformed relative to the austenic 
                 heads 
                 formation must be provided 
               
               
                   
                 shape. The shape change causes 
                 Low voltage operation 
                 High current operation 
               
               
                   
                 ejection of a drop. 
                   
                 Requires pre-stressing to distort 
               
               
                   
                   
                   
                 the martensitic state 
               
               
                 Linear 
                 Linear magnetic actuators 
                 Linear Magnetic actuators can 
                 Requires unusual semiconductor 
                 IJ12 
               
               
                 Magnetic 
                 include the Linear Induction 
                 be constructed with high thrust, 
                 materials such as soft magnetic 
               
               
                 Actuator 
                 Actuator (LIA), Linear 
                 long travel, and high efficiency 
                 alloys (e.g. CoNiFe) 
               
               
                   
                 Permanent Magnet Synchronous 
                 using planar semiconductor fab- 
                 Some varieties also require 
               
               
                   
                 Actuator (LPMSA), Linear 
                 rication techniques 
                 permanent magnetic materials 
               
               
                   
                 Reluctance Synchronous 
                 Long actuator travel is available 
                 such as Neodymium iron boron 
               
               
                   
                 Actuator (LRSA), Linear 
                 Medium force is available 
                 (NdFeB) 
               
               
                   
                 Switched Reluctance Actuator 
                 Low voltage operation 
                 Requires complex multiphase 
               
               
                   
                 (LSRA), and the Linear Stepper 
                   
                 drive circuitry 
               
               
                   
                 Actuator (LSA). 
                   
                 High current operation 
               
            
           
           
               
            
               
                 BASIC OPERATION MODE 
               
            
           
           
               
               
               
               
               
            
               
                 Actuator 
                 This is the simplest mode of 
                 Simple operation 
                 Drop repetition rate is usually 
                 Thermal ink jet 
               
               
                 directly pushes 
                 operation: the actuator directly 
                 No external fields required 
                 limited to around 10 kHz. How- 
                 Piezoelectric ink jet 
               
               
                 ink 
                 supplies sufficient kinetic energy 
                 Satellite drops can be avoided if 
                 ever, this is not fundamental 
                 IJ01, IJ02, IJ03, IJ04, IJ05, IJ06, 
               
               
                   
                 to expel the drop. The drop must 
                 drop velocity is less than 4 m/s 
                 to the method, but is related 
                 IJ07, IJ09, IJ11, IJ12, IJ14, IJ16, 
               
               
                   
                 have a sufficient velocity to 
                 Can be efficient, depending 
                 to the refill method normally 
                 IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, 
               
               
                   
                 overcome the surface tension. 
                 upon the actuator used 
                 used 
                 IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, 
               
               
                   
                   
                   
                 All of the drop kinetic energy 
                 IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, 
               
               
                   
                   
                   
                 must be provided by the actuator 
                 IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 
               
               
                   
                   
                   
                 Satellite drops usually form if 
               
               
                   
                   
                   
                 drop velocity is greater than 
               
               
                   
                   
                   
                 4.5 m/s 
               
               
                 Proximity 
                 The drops to be printed are 
                 Very simple print head fabrica- 
                 Requires close proximity 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 selected by some manner (e.g. 
                 tion can be used 
                 between the print head and the 
                 and related patent applications 
               
               
                   
                 thermally induced surface 
                 The drop selection means does 
                 print media or transfer roller 
               
               
                   
                 tension reduction of pressurized 
                 not need to provide the energy 
                 May require two print heads 
               
               
                   
                 ink). Selected drops are 
                 required to separate the drop 
                 printing alternate rows of the 
               
               
                   
                 separated from the ink in the 
                 from the nozzle 
                 image 
               
               
                   
                 nozzle by contact with the print 
                   
                 Monolithic color print heads are 
               
               
                   
                 medium or a transfer roller. 
                   
                 difficult 
               
               
                 Electrostatic 
                 The drops to be printed are 
                 Very simple print head fabri- 
                 Requires very high electrostatic 
                 Silverbrook, EP 0771 658 A2 
               
               
                 pull on ink 
                 selected by some manner (e.g. 
                 cation can be used 
                 field 
                 and related patent applications 
               
               
                   
                 thermally induced surface 
                 The drop selection means does 
                 Electrostatic field for small 
                 Tone-Jet 
               
               
                   
                 tension reduction of pressurized 
                 not need to provide the energy 
                 nozzle sizes is above air break- 
               
               
                   
                 ink). Selected drops are 
                 required to separate the drop 
                 down 
               
               
                   
                 separated from the ink in the 
                 from the nozzle 
                 Electrostatic field may attract 
               
               
                   
                 nozzle by a strong electric field. 
                   
                 dust 
               
               
                 Magnetic 
                 The drops to be printed are 
                 Very simple print head fabrica- 
                 Requires magnetic ink 
                 Silverbrook, EP 0771 658 A2 
               
               
                 pull on ink 
                 selected by some manner (e.g. 
                 tion can be used 
                 Ink colors other than black are 
                 and related patent applications 
               
               
                   
                 thermally induced surface 
                 The drop selection means does 
                 difficult 
               
               
                   
                 tension reduction of pressurized 
                 not need to provide the energy 
                 Requires very high magnetic 
               
               
                   
                 ink). Selected drops are 
                 required to separate the drop 
                 fields 
               
               
                   
                 separated from the ink in the 
                 from the nozzle 
               
               
                   
                 nozzle by a strong magnetic 
               
               
                   
                 field acting on the magnetic ink. 
               
               
                 Shutter 
                 The actuator moves a shutter to 
                 High speed (&gt;50 kHz) operation 
                 Moving parts are required 
                 IJ13, IJ17, IJ21 
               
               
                   
                 block ink flow the nozzle. The 
                 can be achieved due to reduced 
                 Requires ink pressure modulator 
               
               
                   
                 ink pressure is pulsed at a 
                 refill time 
                 Friction and wear must be con- 
               
               
                   
                 multiple of the drop ejection 
                 Drop timing can be very 
                 sidered 
               
               
                   
                 frequency. 
                 accurate 
                 Stiction is possible 
               
               
                   
                   
                 The actuator energy can be very 
               
               
                   
                   
                 low 
               
               
                 Shuttered 
                 The actuator moves a shutter to 
                 Actuators with small travel can 
                 Moving parts are required 
                 IJ08, IJ15, IJ18, IJ19 
               
               
                 grill 
                 block ink flow through a grill to 
                 be used 
                 Requires ink pressure modulator 
               
               
                   
                 the nozzle. The shutter move- 
                 Actuators with small force can 
                 Friction and wear must be con- 
               
               
                   
                 ment need only be equal to the 
                 be used 
                 sidered 
               
               
                   
                 width of the grill holes. 
                 High speed (&gt;50 kHz) operation 
                 Stiction is possible 
               
               
                   
                   
                 can be achieved 
               
               
                 Pulsed mag- 
                 A pulsed magnetic field attracts 
                 Extremely low energy operation 
                 Requires an external pulsed 
                 IJ10 
               
               
                 netic pull on 
                 an ‘ink pusher’ at the drop 
                 is possible 
                 magnetic field 
               
               
                 ink pusher 
                 ejection frequency. An actuator 
                 No heat dissipation problems 
                 Requires special materials for 
               
               
                   
                 controls a catch, which prevents 
                   
                 both the actuator and the ink 
               
               
                   
                 the ink pusher from moving 
                   
                 pusher 
               
               
                   
                 when a drop is not to be ejected. 
                   
                 Complex construction 
               
            
           
           
               
            
               
                 AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) 
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 The actuator directly fires the 
                 Simplicity of construction 
                 Drop ejection energy must be 
                 Most ink jets, including piezo- 
               
               
                   
                 ink drop, and there is no external 
                 Simplicity of operation 
                 supplied by individual nozzle 
                 electric and thermal bubble. 
               
               
                   
                 field or other mechanism 
                 Small physical size 
                 actuator 
                 IJ01, IJ02, IJ03, IJ04, IJ05, IJ07, 
               
               
                   
                 required. 
                   
                   
                 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 ink 
                 The ink pressure oscillates, pro- 
                 Oscillating ink pressure can 
                 Requires external ink pressure 
                 Silverbrook, EP 0771 658 A2 
               
               
                 pressure 
                 viding much of the drop ejection 
                 provide a refill pulse, allowing 
                 oscillator 
                 and related patent applications 
               
               
                 (including 
                 energy. The actuator selects 
                 higher operating speed 
                 Ink pressure phase and 
                 IJ08, IJ13, IJ15, IJ17, IJ18, IJ19, 
               
               
                 acoustic 
                 which drops are to be fired by 
                 The actuators may operate with 
                 amplitude must be carefully 
                 IJ21 
               
               
                 stimulation) 
                 selectively blocking or enabling 
                 much lower energy 
                 controlled 
               
               
                   
                 nozzles. The ink pressure 
                 Acoustic lenses can be used to 
                 Acoustic reflections in the ink 
               
               
                   
                 oscillation may be achieved by 
                 focus the sound on the nozzles 
                 chamber must be designed for 
               
               
                   
                 vibrating the print head, or 
               
               
                   
                 preferably by an actuator in the 
               
               
                   
                 ink supply. 
               
               
                 Media 
                 The print head is placed in close 
                 Low power 
                 Precision assembly required 
                 Silverbrook, EP 0771 658 A2 
               
               
                 proximity 
                 proximity to the print medium. 
                 High accuracy 
                 Paper fibers may cause problems 
                 and related patent applications 
               
               
                   
                 Selected drops protrude from the 
                 Simple print head construction 
                 Cannot print on rough substrates 
               
               
                   
                 print head further than 
               
               
                   
                 unselected drops, and contact the 
               
               
                   
                 print medium. The drop soaks 
               
               
                   
                 into the medium fast enough to 
               
               
                   
                 cause drop separation. 
               
               
                 Transfer roller 
                 Drops are printed to a transfer 
                 High accuracy 
                 Bulky 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 roller instead of straight to the 
                 Wide range of print substrates 
                 Expensive 
                 and related patent applications 
               
               
                   
                 print medium. A transfer roller 
                 can be used 
                 Complex construction 
                 Tektronix hot melt piezoelectric 
               
               
                   
                 can also be used for proximity 
                 Ink can be dried on the transfer 
                   
                 ink jet 
               
               
                   
                 drop separation. 
                 roller 
                   
                 Any of the IJ series 
               
               
                 Electrostatic 
                 An electric field is used to 
                 Low power 
                 Field strength required for 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 accelerate selected drops 
                 Simple print head construction 
                 separation of small drops is near 
                 and related patent applications 
               
               
                   
                 towards the print medium. 
                   
                 or above air breakdown 
                 Tone-Jet 
               
               
                 Direct mag- 
                 A magnetic field is used to 
                 Low power 
                 Requires magnetic ink 
                 Silverbrook, EP 0771 658 A2 
               
               
                 netic field 
                 accelerate selected drops of 
                 Simple print head construction 
                 Requires strong magnetic field 
                 and related patent applications 
               
               
                   
                 magnetic ink towards the print 
               
               
                   
                 medium. 
               
               
                 Cross magnetic 
                 The print head is placed in a 
                 Does not require magnetic 
                 Requires external magnet 
                 IJ06, IJ16 
               
               
                 field 
                 constant magnetic field. The 
                 materials to be integrated in the 
                 Current densities may be high, 
               
               
                   
                 Lorenz force in a current carry- 
                 print head manufacturing 
                 resulting in electromigration 
               
               
                   
                 ing wire is used to move the 
                 process 
                 problems 
               
               
                   
                 actuator. 
               
               
                 Pulsed mag- 
                 A pulsed magnetic field is used 
                 Very low power operation is 
                 Complex print head construction 
                 IJ10 
               
               
                 netic field 
                 to cyclically attract a paddle, 
                 possible 
                 Magnetic materials required in 
               
               
                   
                 which pushes on the ink. A 
                 Small print head size 
                 print head 
               
               
                   
                 small actuator moves a catch, 
               
               
                   
                 which selectively prevents the 
               
               
                   
                 paddle from moving. 
               
            
           
           
               
            
               
                 ACTUATOR AMPLIFICATION OR MODIFICATION METHOD 
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 No actuator mechanical amplifi- 
                 Operational simplicity 
                 Many actuator mechanisms have 
                 Thermal Bubble Ink jet 
               
               
                   
                 cation is used. The actuator 
                   
                 insufficient travel, or insufficient 
                 IJ01, IJ02, IJ06, IJ07, IJ16, IJ25, 
               
               
                   
                 directly drives the drop ejection 
                   
                 force, to efficiently drive the 
                 IJ26 
               
               
                   
                 process. 
                   
                 drop ejection process 
               
               
                 Differential 
                 An actuator material expands 
                 Provides greater travel in a 
                 High stresses are involved 
                 Piezoelectric 
               
               
                 expansion 
                 more on one side than on the 
                 reduced print head area 
                 Care must be taken that the 
                 IJ03, IJ09, IJ17, IJ18, IJ19, IJ20, 
               
               
                 bend actuator 
                 other. The expansion may be 
                   
                 materials do not delaminate 
                 IJ21, IJ22, IJ23, IJ24, IJ27, IJ29, 
               
               
                   
                 thermal, piezoelectric, magneto- 
                   
                 Residual bend resulting from 
                 IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, 
               
               
                   
                 strictive, or other mechanism. 
                   
                 high temperature or high stress 
                 IJ36, IJ37, IJ38, IJ39, IJ42, IJ43, 
               
               
                   
                 The bend actuator converts a 
                   
                 during formation 
                 IJ44 
               
               
                   
                 high force low travel actuator 
               
               
                   
                 mechanism to high travel, lower 
               
               
                   
                 force mechanism. 
               
               
                 Transient bend 
                 A trilayer bend actuator where 
                 Very good temperature stability 
                 High stresses are involved 
                 IJ40, IJ41 
               
               
                 actuator 
                 the two outside layers are 
                 High speed, as a new drop can 
                 Care must be taken that the 
               
               
                   
                 identical. This cancels bend due 
                 be fired before heat dissipates 
                 materials do not delaminate 
               
               
                   
                 to ambient temperature and 
                 Cancels residual stress of 
               
               
                   
                 residual stress. The actuator only 
                 formation 
               
               
                   
                 responds to transient heating of 
               
               
                   
                 one side or the other. 
               
               
                 Reverse spring 
                 The actuator loads a spring. 
                 Better coupling to the ink 
                 Fabrication complexity 
                 IJ05, IJ11 
               
               
                   
                 When the actuator is turned off, 
                   
                 High stress in 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 stack 
                 A series of thin actuators are 
                 Increased travel 
                 Increased fabrication complexity 
                 Some piezoelectric ink jets 
               
               
                   
                 stacked. This can be appropriate 
                 Reduced drive voltage 
                 Increased possibility of short 
                 IJ04 
               
               
                   
                 where actuators require high 
                   
                 circuits due to pinholes 
               
               
                   
                 electric field strength, such as 
               
               
                   
                 electrostatic and piezoelectric 
               
               
                   
                 actuators. 
               
               
                 Multiple 
                 Multiple smaller actuators are 
                 Increases the force available 
                 Actuator forces may not added 
                 IJ12, IJ13, IJ18, IJ20, IJ22, IJ28, 
               
               
                 actuators 
                 used simultaneously to move the 
                 from an actuator 
                 linearly, reducing efficiency 
                 IJ42, IJ43 
               
               
                   
                 ink. Each actuator need provide 
                 Multiple actuators can be 
               
               
                   
                 only a portion of the force 
                 positioned to control ink flow 
               
               
                   
                   
                 accurately 
               
               
                   
                 required. 
               
               
                 Linear Spring 
                 A linear spring is used to 
                 Matches low travel actuator with 
                 Requires print head area for the 
                 IJ15 
               
               
                   
                 transform a motion with small 
                 higher travel requirements 
                 spring 
               
               
                   
                 travel and high force into a 
                 Non-contact method of motion 
               
               
                   
                 longer travel, lower force 
                 transformation 
               
               
                   
                 motion. 
               
               
                 Coiled actuator 
                 A bend actuator is coiled to 
                 Increased travel 
                 Generally restricted to planar 
                 IJ17, IJ21, IJ34, IJ35 
               
               
                   
                 provide greater travel in a 
                 Reduced chip area 
                 implementations due to extreme 
               
               
                   
                 reduced chip area. 
                 Planar implementations are 
                 fabrication difficulty in other 
               
               
                   
                   
                 relatively easy to fabricate. 
                 orientations. 
               
               
                 Flexure bend 
                 A bend actuator has a small 
                 Simple means of increasing 
                 Care must be taken not to 
                 IJ10, IJ19, IJ33 
               
               
                 actuator 
                 region near the fixture point, 
                 travel of a bend actuator 
                 exceed the elastic limit in the 
               
               
                   
                 which flexes much more readily 
                   
                 flexure area 
               
               
                   
                 than the remainder of the 
                   
                 Stress distribution is very 
               
               
                   
                 actuator. The actuator flexing is 
                   
                 uneven 
               
               
                   
                 effectively converted from an 
                   
                 Difficult to accurately model 
               
               
                   
                 even coiling to an angular bend, 
                   
                 with finite element analysis 
               
               
                   
                 resulting in greater travel of the 
               
               
                   
                 actuator tip. 
               
               
                 Catch 
                 The actuator controls a small 
                 Very low actuator energy 
                 Complex construction 
                 IJ10 
               
               
                   
                 catch. The catch either enables 
                 Very small actuator size 
                 Requires external force 
               
               
                   
                 or disables movement of an ink 
                   
                 Unsuitable for pigmented inks 
               
               
                   
                 pusher that is controlled in a 
               
               
                   
                 bulk manner. 
               
               
                 Gears 
                 Gears can be used to increase 
                 Low force, low travel actuators 
                 Moving parts are required 
                 IJ13 
               
               
                   
                 travel at the expense of duration. 
                 can be used 
                 Several actuator cycles are 
               
               
                   
                 Circular gears, rack and pinion, 
                 Can be fabricated using standard 
                 required 
               
               
                   
                 ratchets, and other gearing 
                 surface MEMS processes 
                 More complex drive electronics 
               
               
                   
                 methods can be used. 
                   
                 Complex construction 
               
               
                   
                   
                   
                 Friction, friction, and wear are 
               
               
                   
                   
                   
                 possible 
               
               
                 Buckle plate 
                 A buckle plate can be used to 
                 Very fast movement achievable 
                 Must stay within elastic limits of 
                 S. Hirata et al, “An Ink-jet Head 
               
               
                   
                 change a slow actuator into a 
                   
                 the materials for long device life 
                 Using Diaphragm Micro- 
               
               
                   
                 fast motion. It can also convert 
                   
                 High stresses involved 
                 actuator”, Proc. IEEE MEMS, 
               
               
                   
                 a high force, low travel actuator 
                   
                 Generally high power require- 
                 Feb. 1996, pp 418-423. 
               
               
                   
                 into a high travel, medium force 
                   
                 ment 
                 IJ18, IJ27 
               
               
                   
                 motion. 
               
               
                 Tapered mag- 
                 A tapered magnetic pole can 
                 Linearizes the magnetic force/ 
                 Complex construction 
                 IJ14 
               
               
                 netic pole 
                 increase travel at the expense of 
                 distance curve 
               
               
                   
                 force. 
               
               
                 Lever 
                 A lever and fulcrum is used to 
                 Matches low travel actuator with 
                 High stress around the fulcrum 
                 IJ32, IJ36, IJ37 
               
               
                   
                 transform a motion with small 
                 higher travel requirements 
               
               
                   
                 travel and high force into a 
                 Fulcrum area has no linear 
               
               
                   
                 motion with longer travel and 
                 movement, and can be used for a 
               
               
                   
                 lower force. The lever can also 
                 fluid seal 
               
               
                   
                 reverse the direction of travel. 
               
               
                 Rotary 
                 The actuator is connected to a 
                 High mechanical advantage 
                 Complex construction 
                 IJ28 
               
               
                 impeller 
                 rotary impeller. A small angular 
                 The ratio of force to travel of 
                 Unsuitable for pigmented inks 
               
               
                   
                 deflection of the actuator results 
                 the actuator can be matched to 
               
               
                   
                 in a rotation of the impeller 
                 the nozzle requirements by 
               
               
                   
                 vanes, which push the ink 
                 varying the number of impeller 
               
               
                   
                 against stationary vanes and out 
                 vanes 
               
               
                   
                 of the nozzle. 
               
               
                 Acoustic lens 
                 A refractive or diffractive (e.g. 
                 A moving parts 
                 Large area required 
                 1993 Hadimioglu et al, EUP 
               
               
                   
                 zone plate) acoustic lens is used 
                   
                 Only relevant for acoustic ink 
                 550,192 
               
               
                   
                 to concentrate sound waves. 
                   
                 jets 
                 1993 Elrod et al, EUP 572,220 
               
               
                 Sharp conduc- 
                 A sharp point is used to con- 
                 Simple construction 
                 Difficult to fabricate using 
                 Tone-jet 
               
               
                 tive point 
                 centrate an electrostatic field. 
                   
                 standard VLSI processes for a 
               
               
                   
                   
                   
                 surface ejecting ink-jet 
               
               
                   
                   
                   
                 Only relevant for electrostatic 
               
               
                   
                   
                   
                 ink jets 
               
            
           
           
               
            
               
                 ACTUATOR MOTION 
               
            
           
           
               
               
               
               
               
            
               
                 Volume expan- 
                 The volume of the actuator 
                 Simple construction in the case 
                 High energy is typically required 
                 Hewlett-Packard Thermal Ink jet 
               
               
                 sion 
                 changes, pushing the ink in all 
                 of thermal ink jet 
                 to achieve volume expansion. 
                 Canon Bubblejet 
               
               
                   
                 directions. 
                   
                 This leads to thermal stress, 
               
               
                   
                   
                   
                 cavitation, and kogation in 
               
               
                   
                   
                   
                 thermal ink jet implementations 
               
               
                 Linear, normal 
                 The actuator moves in a 
                 Efficient coupling to ink drops 
                 High fabrication complexity may 
                 IJ01, IJ02, IJ04, IJ07, IJ11, IJ14 
               
               
                 to chip surface 
                 direction normal to the print 
                 ejected normal to the surface 
                 be required to achieve per- 
               
               
                   
                 head surface. The nozzle is 
                   
                 pendicular motion 
               
               
                   
                 typically in the line of 
               
               
                   
                 movement. 
               
               
                 Parallel to 
                 The actuator moves parallel to 
                 Suitable for planar fabrication 
                 Fabrication complexity 
                 IJ12, IJ13, IJ15, IJ33, IJ34, IJ35, 
               
               
                 chip surface 
                 the print head surface. Drop 
                   
                 Friction 
                 IJ36 
               
               
                   
                 ejection may still be normal to 
                   
                 Stiction 
               
               
                   
                 the surface. 
               
               
                 Membrane 
                 An actuator with a high force 
                 The effective area of the actuator 
                 Fabrication complexity 
                 1982 Howkins U.S. Pat. No. 
               
               
                 push 
                 but small area is used to push a 
                 becomes the membrane area 
                 Actuator size 
                 4,459,601 
               
               
                   
                 stiff membrane that is in contact 
                   
                 Difficulty of integration in a 
               
               
                   
                 with the ink. 
                   
                 VLSI process 
               
               
                 Rotary 
                 The actuator causes the rotation 
                 Rotary levers may be used to 
                 Device complexity 
                 IJ05, IJ08, IJ13, IJ28 
               
               
                   
                 of some element, such a grill or 
                 increase travel 
                 May have friction at a pivot 
               
               
                   
                 impeller 
                 Small chip area requirements 
                 point 
               
               
                 Bend 
                 The actuator bends when 
                 A very small change in 
                 Requires the actuator to be made 
                 1970 Kyser et al U.S. Pat. No. 
               
               
                   
                 energized. This may be due to 
                 dimensions can be converted to 
                 from at least two distinct layers, 
                 3,946,398 
               
               
                   
                 differential thermal expansion, 
                 a large motion. 
                 or to have a thermal difference 
                 1973 Stemme U.S. Pat. No. 
               
               
                   
                 piezoelectric expansion, 
                   
                 across the actuator 
                 3,747,120 
               
               
                   
                 magnetostriction, or other form 
                   
                   
                 IJ03, IJ09, IJ10, IJ19, IJ23, IJ24, 
               
               
                   
                 of relative dimensional change. 
                   
                   
                 IJ25, IJ29, IJ30, IJ31, IJ33, IJ34, 
               
               
                   
                   
                   
                   
                 IJ35 
               
               
                 Swivel 
                 The actuator swivels around a 
                 Allows operation where the net 
                 Inefficient coupling to the ink 
                 IJ06 
               
               
                   
                 central pivot. The motion is 
                 linear force on the paddle is zero 
                 motion 
               
               
                   
                 suitable where there are opposite 
                 Small chip area requirements 
               
               
                   
                 forces applied to opposite sides 
               
               
                   
                 of the paddle, e.g. Lorenz force. 
               
               
                 Straighten 
                 The actuator is normally bent, 
                 Can be used with shape memory 
                 Requires careful balance of 
                 IJ26, IJ32 
               
               
                   
                 and straightens when energized. 
                 alloys where the austenic phase 
                 stresses to ensure that the 
               
               
                   
                   
                 is planar 
                 quiescent bend is accurate 
               
               
                 Double bend 
                 The actuator bends in one 
                 One actuator can be used to 
                 Difficult to make the drops 
                 IJ36, IJ37, IJ38 
               
               
                   
                 direction when one element is 
                 power two nozzles. 
                 ejected by both bend directions 
               
               
                   
                 energized, and bends the other 
                 Reduced chip size. 
                 identical. 
               
               
                   
                 way when another element is 
                 Not sensitive to ambient 
                 A small efficiency loss 
               
               
                   
                 energized. 
                 temperature 
                 compared to equivalent single 
               
               
                   
                   
                   
                 bend actuators. 
               
               
                 Shear 
                 Energizing the actuator causes a 
                 Can increase the effective travel 
                 Not readily applicable to other 
                 1985 Fishbeck U.S. Pat. No. 
               
               
                   
                 shear motion in the actuator 
                 of piezoelectric actuators 
                 actuator mechanisms 
                 4,584,590 
               
               
                   
                 material. 
               
               
                 Radial con- 
                 The actuator squeezes an ink 
                 Relatively easy to fabricate 
                 High force required 
                 1970 Zoltan U.S. Pat. No. 
               
               
                 striction 
                 reservoir, forcing ink from a 
                 single nozzles from glass tubing 
                 Inefficient 
                 3,683,212 
               
               
                   
                 constricted nozzle. 
                 as macroscopic structures 
                 Difficult to integrate with VLSI 
               
               
                   
                   
                   
                 processes 
               
               
                 Coil/uncoil 
                 A coiled actuator uncoils or coils 
                 Easy to fabricate as a planar 
                 Difficult to fabricate for non- 
                 IJ17, IJ21, IJ34, IJ35 
               
               
                   
                 more tightly. The motion of the 
                 VLSI process 
                 planar devices 
               
               
                   
                 free end of the actuator ejects 
                 Small area required, therefore 
                 Poor out-of-plane stiffness 
               
               
                   
                 the ink. 
                 low cost 
               
               
                 Bow 
                 The actuator bows (or buckles) 
                 Can increase the speed of travel 
                 Maximum travel is constrained 
                 IJ16, IJ18, IJ27 
               
               
                   
                 in the middle when energized. 
                 Mechanically rigid 
                 High force required 
               
               
                 Push-Pull 
                 Two actuators control a shutter. 
                 The structure is pinned at both 
                 Not readily suitable for ink jets 
                 IJ18 
               
               
                   
                 One actuator pulls the shutter, 
                 ends, so has a high out-of-plane 
                 which directly push the ink 
               
               
                   
                 and the other pushes it. 
                 rigidity 
               
               
                 Curl inwards 
                 A set of actuators curl inwards 
                 Good fluid flow to the region 
                 Design complexity 
                 IJ20, IJ42 
               
               
                   
                 to reduce the volume of ink that 
                 behind the actuator increases 
               
               
                   
                 they enclose. 
                 efficiency 
               
               
                 Curl outwards 
                 A set of actuators curl outwards, 
                 Relatively simple construction 
                 Relatively large chip area 
                 IJ43 
               
               
                   
                 pressurizing ink in a chamber 
               
               
                   
                 surrounding the actuators, and 
               
               
                   
                 expelling ink from a nozzle in 
               
               
                   
                 the chamber. 
               
               
                 Iris 
                 Multiple vanes enclose a volume 
                 High efficiency 
                 High fabrication complexity 
                 IJ22 
               
               
                   
                 of ink. These simultaneously 
                 Small chip area 
                 Not suitable for pigmented inks 
               
               
                   
                 rotate, reducing the volume 
               
               
                   
                 between the vanes. 
               
               
                 Acoustic 
                 The actuator vibrates at a high 
                 The actuator can be physically 
                 Large area required for efficient 
                 1993 Hadimioglu et al, EUP 
               
               
                 vibration 
                 frequency. 
                 distant from the ink 
                 operation at useful frequencies 
                 550,192 
               
               
                   
                   
                   
                 Acoustic coupling and crosstalk 
                 1993 Elrod et al, EUP 572,220 
               
               
                   
                   
                   
                 Complex drive circuitry 
               
               
                   
                   
                   
                 Poor control of drop volume and 
               
               
                   
                   
                   
                 position 
               
               
                 None 
                 In various ink jet designs the 
                 No moving parts 
                 Various other tradeoffs are 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 actuator does not move. 
                   
                 required to eliminate moving 
                 and related patent applications 
               
               
                   
                   
                   
                 parts 
                 Tone-jet 
               
            
           
           
               
            
               
                 NOZZLE REFILL METHOD 
               
            
           
           
               
               
               
               
               
            
               
                 Surface tension 
                 This is the normal way that ink 
                 Fabrication simplicity 
                 Low speed 
                 Thermal ink jet 
               
               
                   
                 jets are refilled. After the 
                 Operational simplicity 
                 Surface tension force relatively 
                 Piezoelectric ink jet 
               
               
                   
                 actuator is energized, it typically 
                   
                 small compared to actuator force 
                 IJ01-IJ07, IJ10-IJ14, IJ16, IJ20, 
               
               
                   
                 returns rapidly to its normal 
                   
                 Long refill time usually 
                 IJ22-IJ45 
               
               
                   
                 position. This rapid return sucks 
                   
                 dominates the total repetition 
               
               
                   
                 in air 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 chamber is 
                 High speed 
                 Requires common ink pressure 
                 IJ08, IJ13, IJ15, IJ17, IJ18, IJ19, 
               
               
                 oscillating 
                 provided at a pressure that 
                 Low actuator energy, as the 
                 oscillator 
                 IJ21 
               
               
                 ink pressure 
                 oscillates at twice the drop 
                 actuator need only open or close 
                 May not be suitable for 
               
               
                   
                 ejection frequency. When a drop 
                 the shutter, instead of ejecting 
                 pigmented inks 
               
               
                   
                 is to be ejected, the shutter is 
                 the ink drop 
               
               
                   
                 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 actuator 
                 After the main actuator has 
                 High speed, as the nozzle is 
                 Requires two independent 
                 IJ09 
               
               
                   
                 ejected a drop a second (refill) 
                 actively refilled 
                 actuators per 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 ink 
                 The ink is held a slight positive 
                 High refill rate, therefore a high 
                 Surface spill must be prevented 
                 Silverbrook, EP 0771 658 A2 
               
               
                 pressure 
                 pressure. After the ink drop is 
                 drop repetition rate is possible 
                 Highly hydrophobic print head 
                 and related patent applications 
               
               
                   
                 ejected, the nozzle chamber fills 
                   
                 surfaces are required 
                 Alternate for: IJ01-IJ07, IJ10- 
               
               
                   
                 quickly as surface tension and 
                   
                   
                 IJ14, IJ16, IJ20, IJ22-IJ45 
               
               
                   
                 ink pressure both operate to 
               
               
                   
                 refill the nozzle. 
               
            
           
           
               
            
               
                 METHOD OF RESTRICTING BACK-FLOW THROUGH INLET 
               
            
           
           
               
               
               
               
               
            
               
                 Long inlet 
                 The ink inlet channel to the 
                 Design simplicity 
                 Restricts refill rate 
                 Thermal ink jet 
               
               
                 channel 
                 nozzle chamber is made long 
                 Operational simplicity 
                 May result in a relatively large 
                 Piezoelectric ink jet 
               
               
                   
                 and relatively narrow, relying on 
                 Reduces crosstalk 
                 chip area 
                 IJ42, IJ43 
               
               
                   
                 viscous drag to reduce inlet 
                   
                 Only partially effective 
               
               
                   
                 back-flow 
               
               
                 Positive ink 
                 The ink is under a positive 
                 Drop selection and separation 
                 Requires a method (such as a 
                 Silverbrook, EP 0771 658 A2 
               
               
                 pressure 
                 pressure, so that in the quiescent 
                 forces can be reduced 
                 nozzle rim or effective hydro- 
                 and related patent applications 
               
               
                   
                 state some of the ink drop 
                 Fast refill time 
                 phobizing, or both) to prevent 
                 Possible operation of the 
               
               
                   
                 already protrudes from the 
                   
                 flooding of the ejection surface 
                 following: IJ01-IJ07, IJ09-IJ12, 
               
               
                   
                 nozzle. This reduces the pressure 
                   
                 of the print head. 
                 IJ14, IJ16, IJ20, IJ22, IJ23-IJ34, 
               
               
                   
                 in the nozzle chamber which is 
                   
                   
                 IJ36-IJ41, IJ44 
               
               
                   
                 required 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 baffles are placed 
                 The refill rate is not as restricted 
                 Design complexity 
                 HP Thermal Ink Jet 
               
               
                   
                 in the inlet ink flow. When the 
                 as the long inlet method. 
                 May increase fabrication 
                 Tektronix piezoelectric ink jet 
               
               
                   
                 actuator is energized, the rapid 
                 Reduces crosstalk 
                 complexity (e.g. Tektronix hot 
               
               
                   
                 ink movement creates eddies 
                   
                 melt Piezoelectric print heads). 
               
               
                   
                 which restrict the flow through 
               
               
                   
                 the inlet. The slower refill 
               
               
                   
                 process is unrestricted, and does 
               
               
                   
                 not result in eddies. 
               
               
                 Flexible flap 
                 In this method recently disclosed 
                 Significantly reduces back-flow 
                 Not applicable to most ink jet 
                 Canon 
               
               
                 restricts inlet 
                 by Canon, the expanding 
                 for edge-shooter thermal ink jet 
                 configurations 
               
               
                   
                 actuator (bubble) pushes on a 
                 devices 
                 Increased fabrication complexity 
               
               
                   
                 flexible flap that restricts the 
                   
                 Inelastic deformation of polymer 
               
               
                   
                 inlet. 
                   
                 flap results in creep over 
               
               
                   
                   
                   
                 extended use 
               
               
                 Inlet filter 
                 A filter is located between the 
                 Additional advantage of ink 
                 Restricts refill rate 
                 IJ04, IJ12, IJ24, IJ27, IJ29, IJ30 
               
               
                   
                 ink inlet and the nozzle 
                 filtration 
                 May result in complex 
               
               
                   
                 chamber. The filter has a 
                 Ink filter may be fabricated with 
                 construction 
               
               
                   
                 multitude of small holes or slots, 
                 no additional process steps 
               
               
                   
                 restricting ink flow. The filter 
               
               
                   
                 also removes particles which 
               
               
                   
                 may block the nozzle. 
               
               
                 Small inlet 
                 The ink inlet channel to the 
                 Design simplicity 
                 Restricts refill rate 
                 IJ02, IJ37, IJ44 
               
               
                 compared to 
                 nozzle chamber has a sub- 
                   
                 May result in a relatively large 
               
               
                 nozzle 
                 stantially smaller cross section 
                   
                 chip area 
               
               
                   
                 than that of the nozzle, resulting 
                   
                 Only partially effective 
               
               
                   
                 in easier ink egress out of the 
               
               
                   
                 nozzle than out of the inlet. 
               
               
                 Inlet shutter 
                 A secondary actuator controls 
                 Increases speed of the ink-jet 
                 Requires separate refill actuator 
                 IJ09 
               
               
                   
                 the position of a shutter, closing 
                 print head operation 
                 and drive circuit 
               
               
                   
                 off the ink inlet when the main 
               
               
                   
                 actuator is energized. 
               
               
                 The inlet is 
                 The method avoids the problem 
                 Back-flow problem is eliminated 
                 Requires careful design to 
                 IJ01, IJ03, IJ05, IJ06, IJ07, IJ10, 
               
               
                 located behind 
                 of inlet back-flow by arranging 
                   
                 minimize the negative pressure 
                 IJ11, IJ14, IJ16, IJ22, IJ23, IJ25, 
               
               
                 the ink-pushing 
                 the ink-pushing surface of the 
                   
                 behind the paddle 
                 IJ28, IJ31, IJ32, IJ33, IJ34, IJ35, 
               
               
                 surface 
                 actuator between the inlet and 
                   
                   
                 IJ36, IJ39, IJ40, IJ41 
               
               
                   
                 the nozzle. 
               
               
                 Part of the 
                 The actuator and a wall of the 
                 Significant reductions in back- 
                 Small increase in fabrication 
                 IJ07, IJ20, IJ26, IJ38 
               
               
                 actuator moves 
                 ink chamber are arranged so that 
                 flow can be achieved 
                 complexity 
               
               
                 to shut off the 
                 the motion of the actuator closes 
                 Compact designs possible 
               
               
                 inlet 
                 off the inlet. 
               
               
                 Nozzle actuator 
                 In some configurations of ink 
                 Ink back-flow problem is 
                 None related to ink back-flow on 
                 Silverbrook, EP 0771 658 A2 
               
               
                 does not result 
                 jet, there is no expansion or 
                 eliminated 
                 actuation 
                 and related patent applications 
               
               
                 in ink back- 
                 movement of an actuator which 
                   
                   
                 Valve-jet 
               
               
                 flow 
                 may cause ink back-flow 
                   
                   
                 Tone-jet 
               
               
                   
                 through the inlet. 
               
            
           
           
               
            
               
                 NOZZLE CLEARING METHOD 
               
            
           
           
               
               
               
               
               
            
               
                 Normal nozzle 
                 All of the nozzles are fired 
                 No added complexity on the 
                 May not be sufficient to displace 
                 Most ink jet systems 
               
               
                 firing 
                 periodically, before the ink has a 
                 print head 
                 dried ink 
                 IJ01, IJ02, IJ03, IJ04, IJ05, IJ06, 
               
               
                   
                 chance to dry. When not in use 
                   
                   
                 IJ07, IJ09, IJ10, IJ11, IJ12, IJ14, 
               
               
                   
                 the nozzles are sealed (capped) 
                   
                   
                 IJ16, IJ20, IJ22, IJ23, IJ24, IJ25, 
               
               
                   
                 against air. The nozzle firing is 
                   
                   
                 IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, 
               
               
                   
                 usually performed during a 
                   
                   
                 IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, 
               
               
                   
                 special clearing cycle, after first 
                   
                   
                 IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, 
               
               
                   
                 moving the print head to a 
                   
                   
                 IJ45 
               
               
                   
                 cleaning station. 
               
               
                 Extra power 
                 In systems which heat the ink, 
                 Can be highly effective if the 
                 Requires higher drive voltage 
                 Silverbrook, EP 0771 658 A2 
               
               
                 to ink heater 
                 but do not boil it under normal 
                 heater is adjacent to the nozzle 
                 for clearing 
                 and related patent applications 
               
               
                   
                 situations, nozzle clearing can be 
                   
                 May require larger drive 
               
               
                   
                 achieved by over-powering the 
                   
                 transistors 
               
               
                   
                 heater and boiling ink at the 
               
               
                   
                 nozzle. 
               
               
                 Rapid success- 
                 The actuator is fired in rapid 
                 Does not require extra drive 
                 Effectiveness depends sub- 
                 May be used with: IJ01, IJ02, 
               
               
                 ion of actuator 
                 succession. In some configura- 
                 circuits on the print head 
                 stantially upon the configuration 
                 IJ03, IJ04, IJ05, IJ06, IJ07, IJ09, 
               
               
                 pulses 
                 tions, this may cause heat build- 
                 Can be readily controlled and 
                 of the ink jet nozzle 
                 IJ10, IJ11, IJ14, IJ16, IJ20, IJ22, 
               
               
                   
                 up at the nozzle which boils the 
                 initiated by digital logic 
                   
                 IJ23, IJ24, IJ25, IJ27, IJ28, IJ29, 
               
               
                   
                 ink, clearing the nozzle. In other 
                   
                   
                 IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, 
               
               
                   
                 situations, it may cause 
                   
                   
                 IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, 
               
               
                   
                 sufficient vibrations to dislodge 
                   
                   
                 IJ43, IJ44, IJ45 
               
               
                   
                 clogged nozzles. 
               
               
                 Extra power to 
                 Where an actuator is not 
                 A simple solution where 
                 Not suitable where there is a 
                 May be used with: IJ03, IJ09, 
               
               
                 ink pushing 
                 normally driven to the limit of 
                 applicable 
                 hard limit to actuator movement 
                 IJ16, IJ20, IJ23, IJ24, IJ25, IJ27, 
               
               
                 actuator 
                 its motion, nozzle clearing may 
                   
                   
                 IJ29, IJ30, IJ31, IJ32, IJ39, IJ40, 
               
               
                   
                 be assisted by providing an 
                   
                   
                 IJ41, IJ42, IJ43, IJ44, IJ45 
               
               
                   
                 enhanced drive signal to the 
               
               
                   
                 actuator. 
               
               
                 Acoustic 
                 An ultrasonic wave is applied to 
                 A high nozzle clearing capability 
                 High implementation cost if 
                 IJ08, IJ13, IJ15, IJ17, IJ18, IJ19, 
               
               
                 resonance 
                 the ink chamber. This wave is of 
                 can be achieved 
                 system does not already include 
                 IJ21 
               
               
                   
                 an appropriate amplitude and 
                 May be implemented at very low 
                 an acoustic actuator 
               
               
                   
                 frequency to cause sufficient 
                 cost in systems which already 
               
               
                   
                 force at the nozzle to clear 
                 include acoustic actuators 
               
               
                   
                 blockages. This is easiest to 
               
               
                   
                 achieve if the ultrasonic wave is 
               
               
                   
                 at a resonant frequency of the 
               
               
                   
                 ink cavity. 
               
               
                 Nozzle clearing 
                 A microfabricated plate is 
                 Can clear severely clogged 
                 Silverbrook, EP 0771 658 A2 
               
               
                 plate 
                 pushed against the nozzles. The 
                 nozzles 
                 and related patent applications 
               
               
                   
                 plate has a post for every nozzle. 
                 Moving parts are required 
               
               
                   
                 A post moves through each 
                 There is risk of damage to the 
               
               
                   
                 nozzle, displacing dried ink. 
                 nozzles 
               
               
                   
                   
                 Accurate fabrication is required 
               
               
                 Ink pressure 
                 The pressure of the ink is 
                 May be effective where other 
                 Requires pressure pump or other 
                 May be used with all IJ series 
               
               
                 pulse 
                 temporarily increased so that 
                 methods cannot be used 
                 pressure actuator 
                 ink jets 
               
               
                   
                 ink streams from all of the 
                   
                 Expensive 
               
               
                   
                 nozzles. This may be used in 
                   
                 Wasteful of ink 
               
               
                   
                 conjunction with actuator 
               
               
                   
                 energizing. 
               
               
                 Print head 
                 A flexible ‘blade’ is wiped 
                 Effective for planar print head 
                 Difficult to use if print head 
                 Many ink jet systems 
               
               
                 wiper 
                 across the print head surface. 
                 surfaces 
                 surface is non-planar or very 
               
               
                   
                 The blade is usually fabricated 
                 Low cost 
                 fragile 
               
               
                   
                 from a flexible polymer, e.g. 
                   
                 Requires mechanical parts 
               
               
                   
                 rubber or synthetic elastomer. 
                   
                 Blade can wear out in high 
               
               
                   
                   
                   
                 volume print systems 
               
               
                 Separate ink 
                 A separate heater is provided at 
                 Can be effective where other 
                 Fabrication complexity 
                 Can be used with many IJ series 
               
               
                 boiling heater 
                 the nozzle although the normal 
                 nozzle clearing methods cannot 
                   
                 ink jets 
               
               
                   
                 drop e-ection mechanism does 
                 be used 
               
               
                   
                 not require it. The heaters do not 
                 Can be implemented at no 
               
               
                   
                 require individual drive circuits, 
                 additional cost in some ink jet 
               
               
                   
                 as many nozzles can be cleared 
                 configurations 
               
               
                   
                 simultaneously, and no imaging 
               
               
                   
                 is required. 
               
            
           
           
               
            
               
                 NOZZLE PLATE CONSTRUCTION 
               
            
           
           
               
               
               
               
               
            
               
                 Electroformed 
                 A nozzle plate is separately 
                 Fabrication simplicity 
                 High temperatures and pressures 
                 Hewlett Packard Thermal Ink jet 
               
               
                 nickel 
                 fabricated from electroformed 
                   
                 are required to bond nozzle plate 
               
               
                   
                 nickel, and bonded to the print 
                   
                 Minimum thickness constraints 
               
               
                   
                 head chip. 
                   
                 Differential thermal expansion 
               
               
                 Laser ablated 
                 Individual nozzle holes are 
                 No masks required 
                 Each hole must be individually 
                 Canon Bubblejet 
               
               
                 or drilled 
                 ablated by an intense UV laser 
                 Can be quite fast 
                 formed 
                 1988 Sercel et al., SPIE, Vol. 
               
               
                 polymer 
                 in a nozzle plate, which is 
                 Some control over nozzle profile 
                 Special equipment required 
                 998 Excimer Beam Applica- 
               
               
                   
                 typically a polymer such as 
                 is possible 
                 Slow where there are many 
                 tions, pp. 76-83 
               
               
                   
                 polyimide or polysulphone 
                 Equipment required is relatively 
                 thousands of nozzles per print 
                 1993 Watanabe et al., U.S. Pat. 
               
               
                   
                   
                 low cost 
                 head 
                 No. 5,208,604 
               
               
                   
                   
                   
                 May produce thin burrs at exit 
               
               
                   
                   
                   
                 holes 
               
               
                 Silicon micro- 
                 A separate nozzle plate is micro- 
                 High accuracy is attainable 
                 Two part construction 
                 K. Bean, IEEE Transactions 
               
               
                 machined 
                 machined from single crystal 
                   
                 High cost 
                 on Electron Devices, Vol. 
               
               
                   
                 silicon, and bonded to the print 
                   
                 Requires precision alignment 
                 ED-25, No. 10, 1978, pp 1185- 
               
               
                   
                 head wafer. 
                   
                 Nozzles may be clogged by 
                 1195 
               
               
                   
                   
                   
                 adhesive 
                 Xerox 1990 Hawkins et al., 
               
               
                   
                   
                   
                   
                 U.S. Pat. No. 4,899,181 
               
               
                 Glass 
                 Fine glass capillaries are drawn 
                 No expensive equipment 
                 Very small nozzle sizes are 
                 1970 Zoltan U.S. Pat. No. 
               
               
                 capillaries 
                 from glass tubing. This method 
                 required 
                 difficult to form 
                 3,683,212 
               
               
                   
                 has been used for making 
                 Simple to make single nozzles 
                 Not suited for mass production 
               
               
                   
                 individual nozzles, but is 
               
               
                   
                 difficult to use for bulk 
               
               
                   
                 manufacturing of print heads 
               
               
                   
                 with thousands of nozzles. 
               
               
                 Monolithic, 
                 The nozzle plate is deposited 
                 High accuracy (&lt;1 μm) 
                 Requires sacrificial layer under 
                 Silverbrook, EP 0771 658 A2 
               
               
                 surface micro- 
                 as a layer using standard VLSI 
                 Monolithic 
                 the nozzle plate to form the 
                 and related patent applications 
               
               
                 machined using 
                 deposition techniques. Nozzles 
                 Low cost 
                 nozzle plate to form the 
                 IJ01, IJ02, IJ04, IJ11, IJ12, IJ17, 
               
               
                 VLSI litho- 
                 are etched in the nozzle plate 
                 Existing processes can be used 
                 nozzle chamber 
                 IJ18, IJ20, IJ22, IJ24, IJ27, IJ28, 
               
               
                 graphic pro- 
                 using VLSI lithography and 
                   
                 Surface may be fragile to the 
                 IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, 
               
               
                 cesses 
                 etching. 
                   
                 touch 
                 IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, 
               
               
                   
                   
                   
                   
                 IJ42, IJ43, IJ44 
               
               
                 Monolithic, 
                 The nozzle plate is a buried 
                 High accuracy (&lt;1 μm) 
                 Requires long etch times 
                 IJ03, IJ05, IJ06, IJ07, IJ08, IJ09, 
               
               
                 etched through 
                 etch stop in the wafer. Nozzle 
                 Monolithic 
                 Requires a support wafer 
                 IJ10, IJ13, IJ14, IJ15, IJ16, IJ19, 
               
               
                 substrate 
                 chambers are etched in the 
                 Low cost 
                   
                 IJ21, IJ23, IJ25, IJ26 
               
               
                   
                 front of the wafer, and the 
                 No differential expansion 
               
               
                   
                 wafer is thinned from the back 
               
               
                   
                 side. Nozzles are then etched 
               
               
                   
                 in the etch stop layer. 
               
               
                 No nozzle plate 
                 Various methods have been tried 
                 No nozzles to become clogged 
                 Difficult to control drop position 
                 Ricoh 1995 Sekiya et al U.S. 
               
               
                   
                 to eliminate the nozzles entirely, 
                   
                 accurately 
                 Pat. No. 5,412,413 
               
               
                   
                 to prevent nozzle clogging. 
                   
                 Crosstalk problems 
                 1993 Hadimioglu et al EUP 
               
               
                   
                 These include thermal bubble 
                   
                   
                 550,192 
               
               
                   
                 mechanisms and acoustic lens 
                   
                   
                 1993 Elrod et al EUP 572,220 
               
               
                   
                 mechanisms 
               
               
                 Trough 
                 Each drop ejector has a trough 
                 Reduced manufacturing 
                 Drop firing direction is 
                 IJ35 
               
               
                   
                 through which a paddle moves. 
                 complexity 
                 sensitive to wicking. 
               
               
                   
                 There is no nozzle plate. 
                 Monolithic 
               
               
                 Nozzle slit 
                 The elimination of nozzle holes 
                 No nozzles to become clogged 
                 Difficult to control drop 
                 1989 Saito et al U.S. Pat. No. 
               
               
                 instead of 
                 and replacement by a slit 
                   
                 position accurately 
                 4,799,068 
               
               
                 individual 
                 encompassing many actuator 
                   
                 Crosstalk problems 
               
               
                 nozzles 
                 positions reduces nozzle 
               
               
                   
                 clogging, but increases cross- 
               
               
                   
                 talk due to ink surface waves 
               
            
           
           
               
            
               
                 DROP EJECTION DIRECTION 
               
            
           
           
               
               
               
               
               
            
               
                 Edge (‘edge 
                 Ink flow is along the surface 
                 Simple construction 
                 Nozzles limited to edge 
                 Canon Bubblejet 1979 Endo 
               
               
                 shooter’) 
                 of the chip, and ink drops are 
                 No silicon etching required 
                 High resolution is difficult 
                 et al GB patent 2,007,162 
               
               
                   
                 ejected from the chip edge. 
                 Good heat sinking via substrate 
                 Fast color printing requires 
                 Xerox heater-in-pit 1990 
               
               
                   
                   
                 Mechanically strong 
                 one print head per color 
                 Hawkins et al U.S. Pat. No. 
               
               
                   
                   
                 Ease of chip handling 
                   
                 4,899,181 
               
               
                   
                   
                   
                   
                 Tone-jet 
               
               
                 Surface (‘roof 
                 Ink flow is along the surface 
                 No bulk silicon etching required 
                 Maximum ink flow is severely 
                 Hewlett-Packard TIJ 1982 
               
               
                 shooter’) 
                 of the chip, and ink drops are 
                 Silicon can make an effective 
                 restricted 
                 Vaught et al U.S. Pat. No. 
               
               
                   
                 ejected from the chip surface, 
                 heat sink 
                   
                 4,490,728 
               
               
                   
                 normal to the plane of the chip. 
                 Mechanical strength 
                   
                 IJ02, IJ11, IJ12, IJ20, IJ22 
               
               
                 Through chip, 
                 Ink flow is through the chip, and 
                 High ink flow 
                 Requires bulking silicon etching 
                 Silverbrook, EP 0771 658 A2 
               
               
                 forward (‘up 
                 ink drops are ejected from the 
                 Suitable for pagewidth print 
                   
                 and related patent applications 
               
               
                 shooter’) 
                 front surface of the chip. 
                 heads 
                   
                 IJ04, IJ17, IJ18, IJ24, IJ27-IJ25 
               
               
                   
                   
                 High nozzle packing density 
               
               
                   
                   
                 therefore low manufacturing cost 
               
               
                 Through chip, 
                 Ink flow is through the chip, and 
                 High ink flow 
                 Requires wafer thinning 
                 IJ01, IJ03, IJ05, IJ06, IJ07, IJ08, 
               
               
                 reverse (‘down 
                 ink drops are ejected from the 
                 Suitable for pagewidth print 
                 Requires special handling during 
                 IJ09, IJ10, IJ13, IJ14, IJ15, IJ16, 
               
               
                 shooter’) 
                 rear surface of the chip. 
                 heads 
                 manufacture 
                 IJ19, IJ21, IJ23, IJ25, IJ26 
               
               
                   
                   
                 High nozzle packing density 
               
               
                   
                   
                 therefore low manufacturing 
               
               
                   
                   
                 cost 
               
               
                 Through 
                 Ink flow is through the actuator, 
                 Suitable for piezoelectric print 
                 Pagewidth print heads require 
                 Epson Stylus 
               
               
                   
                 which is not fabricated as part of 
                 heads 
                 several thousand connections to 
                 Tektronix hot melt piezoelectric 
               
               
                   
                 the same substrate as the drive 
                   
                 drive circuits 
                 ink jets 
               
               
                   
                 transistors. 
                   
                 Cannot be manufactured in 
               
               
                   
                   
                   
                 standard CMOS fabs 
               
               
                   
                   
                   
                 Complex assembly required 
               
            
           
           
               
            
               
                 INK TYPE 
               
            
           
           
               
               
               
               
               
            
               
                 Aqueous, dye 
                 Water based ink which typically 
                 Environmentally friendly 
                 Slow drying 
                 Most existing ink jets 
               
               
                   
                 contains: water, dye, surfactant, 
                 No odor 
                 Corrosive 
                 All IJ series ink jets 
               
               
                   
                 humectant, and biocide. Modern 
                   
                 Bleeds on paper 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 ink dyes have high water- 
                   
                 May strikethrough 
                 and related patent applications 
               
               
                   
                 fastness, light fastness 
                   
                 Cockles paper 
               
               
                 Aqueous, 
                 Water based ink which typically 
                 Environmentally friendly 
                 Slow drying 
                 IJ02, IJ04, IJ21, IJ26, IJ27, IJ30 
               
               
                 pigment 
                 contains: water, pigment, 
                 No odor 
                 Corrosive 
                 Silverbrook, EP 0771 658 A2 
               
               
                   
                 surfactant, humectant, and 
                 Reduced bleed 
                 Pigment may clog nozzles 
                 and related patent applications 
               
               
                   
                 biocide. Pigments have an 
                 Reduced wicking 
                 Pigment may clog actuator 
                 Piezoelectric ink-jets 
               
               
                   
                 advantage in reduced bleed, 
                 Reduced strikethrough 
                 mechanisms 
                 Thermal ink jets (with signifi- 
               
               
                   
                 wicking and strikethrough. 
                   
                 Cockles paper 
                 cant restrictions) 
               
               
                 Methyl Ethyl 
                 MEK is a highly volatile solvent 
                 Very fast drying 
                 Odorous 
                 All IJ series ink jets 
               
               
                 Ketone (MEK) 
                 used for industrial printing on 
                 Prints on various substrates 
                 Flammable 
               
               
                   
                 difficult surfaces such as 
                 such as metals and plastics 
               
               
                   
                 aluminum cans. 
               
               
                 Alcohol 
                 Alcohol based inks can be used 
                 Fast drying 
                 Slight odor 
                 All IJ series ink jets 
               
               
                 (ethanol, 2- 
                 where the printer must operate 
                 Operates at sub-freezing temper- 
                 Flammable 
               
               
                 butanol, and 
                 at temperatures below the 
                 atures 
               
               
                 others) 
                 freezing point of water. An 
                 Reduced paper cockle 
               
               
                   
                 example of this is in-camera 
                 Low cost 
               
               
                   
                 consumer photographic printing. 
               
               
                 Phase change 
                 The ink is solid at room temper- 
                 No drying time-ink instantly 
                 High viscosity 
                 Tektronix hot melt piezoelectric 
               
               
                 (hot melt) 
                 ature, and is melted in the print 
                 freezes on the print medium 
                 Printed ink typically has a 
                 ink jets 
               
               
                   
                 head before jetting. Hot melt 
                 Almost any print medium can be 
                 ‘waxy’ feel 
                 1989 Nowak U.S. Pat. No. 
               
               
                   
                 inks are usually wax based, with 
                 used 
                 Printed pages may ‘block’ 
                 4,820,346 
               
               
                   
                 a melting point around 80° C.. 
                 No paper cockle occurs 
                 Ink temperature may be above 
                 All IJ series ink jets 
               
               
                   
                 After jetting the ink freezes 
                 No wicking occurs 
                 the curie point of permanent 
               
               
                   
                 almost instantly upon contacting 
                 No bleed occurs 
                 magnets 
               
               
                   
                 the print medium or a transfer 
                 No strikethrough occurs 
                 Ink heaters consume power 
               
               
                   
                 roller. 
                   
                 Long warm-up time 
               
               
                 Oil 
                 Oil based inks are extensively 
                 High solubility medium for 
                 High viscosity: this is a signifi- 
                 All IJ series ink jets 
               
               
                   
                 used in offset printing. They 
                 some dyes 
                 cant limitation for use in ink 
               
               
                   
                 have advantages in improved 
                 Does not cockle paper 
                 jets, which usually require a low 
               
               
                   
                 characteristics on paper 
                 Does not wick through paper 
                 viscosity. Some short chain and 
               
               
                   
                 (especially no wicking or 
                   
                 multi-branched oils have a 
               
               
                   
                 cockle). Oil soluble dies and 
                   
                 sufficiently low viscosity. 
               
               
                   
                 pigments are required. 
                   
                 Slow drying 
               
               
                 Microemulsion 
                 A microemulsion is a stable, 
                 Stops ink bleed 
                 Viscosity higher than water 
                 All IJ series ink jets 
               
               
                   
                 self forming emulsion of oil, 
                 High dye solubility 
                 Cost is slightly higher than water 
               
               
                   
                 water, and surfactant. The 
                 Water, oil, and amphiphilic 
                 based ink 
               
               
                   
                 characteristic drop size is less 
                 soluble dies can be used 
                 High surfactant concentration 
               
               
                   
                 than 100 nm, and is determined 
                 Can stabilize pigment 
                 required (around 5%) 
               
               
                   
                 by the preferred curvature of the 
                 suspensions 
               
               
                   
                 surfactant.