# Patent

## Title
Printhead with a two-dimensional array of reciprocating ink nozzles

## Abstract

A printhead is provided for an inkjet printer. The printhead includes a two-dimensional array of ink nozzle arrangements. Each nozzle arrangement includes a wafer portion defining both a nozzle chamber for storing ink and an ink supply channel in fluid communication with the nozzle chamber. A cover covers the nozzle chamber and defines a nozzle rim from which a plurality of supports extends outwardly. The cover includes a plurality of actuators extending inwardly toward the nozzle rim between respective pairs of adjacent supports and terminates in free ends. The actuators include internal heating elements which can be actuated so that the free ends reciprocate into and out of the nozzle chamber to eject ink out through the nozzle rim.

## Background
CROSS REFERENCES TO RELATED APPLICATIONS
This present application is a Continuation of U.S. Application No. 11/520,577, filed on Sep. 14, 2006, now issued U.S. Pat. No. 7,284,838, which is a Continuation of U.S. Application No. 11/202,332 filed Aug. 12, 2005, now issued U.S. Pat. No. 7,147,303, which is a Continuation of U.S. Application No. 10/636,256 filed Aug. 8, 2003, now issued U.S. Pat. No. 6,959,982, which is a Continuation of U.S. Application No. 09/854,703 filed May 14, 2001, now issued U.S. Pat. No. 6,981,757, which is a Continuation application of U.S. Application No. 09/112,806 filed on Jul. 10, 1998, now issued U.S. Pat. No. 6,247,790, the entire contents of which are herein incorporated by reference.
The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.












U.S. PAT. NO./


CROSS-REFERENCED
PATENT APPLICATION (CLAIMING


AUSTRALIAN
RIGHT OF PRIORITY


PROVISIONAL PATENT
FROM AUSTRALIAN


APPLICATION NO.
PROVISIONAL APPLICATION)







PO7991
6,750,901


PO8505
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PO7988
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PO9395
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PO8017
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PO8014
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PO8025
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PO8032
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PO7999
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PO8030
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PO7997
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PO7979
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PO7978
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PO7982
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PO7989
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PO8019
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PO7980
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PO8018
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PO7938
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PO8016
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PO8024
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PO7939
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PO8501
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PO8500
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PO7987
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PO8022
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PO8497
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PO8020
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PO8504
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PO8000
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PO7934
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PO7990
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PO8499
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PO8502
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PO7981
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PO7986
6,850,274


PO7983
09/113,054


PO8026
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PO8028
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PO9394
6,357,135


PO9397
6,271,931


PO9398
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PO9399
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PO9400
6,665,008


PO9401
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PO9403
6,305,770


PO9405
6,289,262


PP0959
6,315,200


PP1397
6,217,165


PP2370
6,786,420


PO8003
6,350,023


PO8005
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PO8066
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PO8072
6,213,588


PO8040
6,213,589


PO8071
6,231,163


PO8047
6,247,795


PO8035
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PO8044
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PO8063
6,257,704


PO8057
6,416,168


PO8056
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PO8069
6,257,705


PO8049
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PO8036
6,234,610


PO8048
6,247,793


PO8070
6,264,306


PO8067
6,241,342


PO8001
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PO8038
6,264,307


PO8033
6,254,220


PO8002
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PO8068
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PO8062
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PO8034
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PO8039
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PO8041
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PO8004
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PO8037
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PO8043
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PO8042
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PO8064
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PO9389
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PO9391
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PP0888
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PP0891
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PP0890
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PP0873
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PP0993
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PP0890
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PP1398
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PP2592
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PP2593
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PP3991
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PP3987
6,247,790


PP3985
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PP3983
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PO7935
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PO7936
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PO7937
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PO8061
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PO8054
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PO8065
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PO8055
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PO8053
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PO8078
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PO7933
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PO7950
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PO7949
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PO8060
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PO8059
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PO8073
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PO8076
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PO8075
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PO8079
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PO8050
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PO8052
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PO7948
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PO7951
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PO8074
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PO7941
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PO8077
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PO8058
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PO8051
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PO8045
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PO8046
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PO9390
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PO9392
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PP0889
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PP0887
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PP0882
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PP0874
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PP1396
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PP3989
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PP2591
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PP3990
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PP3986
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PP3984
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PP0895
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PP0869
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PO8010
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PO7946
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PP0894
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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
FIELD OF THE INVENTION
The present invention relates to the field of inkjet printing and, in particular, discloses an inverted radial back-curling thermoelastic ink jet printing mechanism.
BACKGROUND OF THE INVENTION
Many different types of printing mechanisms have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles, has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different forms. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including a step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode form of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 which discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclose ink jet printing techniques which rely on the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction and operation, durability and consumables.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention, there is provided a nozzle arrangement for an ink jet printhead, the arrangement comprising: a nozzle chamber defined in a wafer substrate for the storage of ink to be ejected; an ink ejection port having a rim formed on one wall of the chamber; and a series of actuators attached to the wafer substrate, and forming a portion of the wall of the nozzle chamber adjacent the rim, the actuator paddles further being actuated in unison so as to eject ink from the nozzle chamber via the ink ejection nozzle.
The actuators can include a surface which bends inwards away from the centre of the nozzle chamber upon actuation. The actuators are preferably actuated by means of a thermal actuator device. The thermal actuator device may comprise a conductive resistive heating element encased within a material having a high coefficient of thermal expansion. The element can be serpentine to allow for substantially unhindered expansion of the material. The actuators are preferably arranged radially around the nozzle rim.
The actuators can form a membrane between the nozzle chamber and an external atmosphere of the arrangement and the actuators bend away from the external atmosphere to cause an increase in pressure within the nozzle chamber thereby initiating a consequential ejection of ink from the nozzle chamber. The actuators can bend away from a central axis of the nozzle chamber.
The nozzle arrangement can be formed on the wafer substrate utilizing micro-electro mechanical techniques and further can comprise an ink supply channel in communication with the nozzle chamber. The ink supply channel may be etched through the wafer. The nozzle arrangement may include a series of struts which support the nozzle rim.
The arrangement can be formed adjacent to neighbouring arrangements so as to form a pagewidth printhead.



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:
FIGS. 1-3 are schematic sectional views illustrating the operational principles of the preferred embodiment;
FIG. 4(a) and FIG. 4(b) are again schematic sections illustrating the operational principles of the thermal actuator device;
FIG. 5 is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with the preferred embodiments;
FIGS. 6-13 are side perspective views, partly in section, illustrating the manufacturing steps of the preferred embodiments;
FIG. 14 illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of the preferred embodiment;
FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23; and
FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing steps in one form of construction of a nozzle arrangement in accordance with the invention.



DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
In the preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port using a series of radially positioned thermal actuator devices that are arranged about the ink ejection port and are activated to pressurize the ink within the nozzle chamber thereby causing the ejection of ink through the ejection port.
Turning now to FIGS. 1, 2 and 3, there is illustrated the basic operational principles of the preferred embodiment. FIG. 1 illustrates a single nozzle arrangement 1 in its quiescent state. The arrangement 1 includes a nozzle chamber 2 which is normally filled with ink so as to form a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 is formed within a wafer 5. The nozzle chamber 2 is supplied with ink via an ink supply channel 6 which is etched through the wafer 5 with a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom.
A top of the nozzle arrangement 1 includes a series of radially positioned actuators 8, 9. These actuators comprise a polytetrafluoroethylene (PTFE) layer and an internal serpentine copper core 17. Upon heating of the copper core 17, the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuators 8, 9. Hence, when it is desired to eject ink from the ink ejection port 4, a current is passed through the actuators 8, 9 which results in them bending generally downwards as illustrated in FIG. 2. The downward bending movement of the actuators 8, 9 results in a substantial increase in pressure within the nozzle chamber 2. The increase in pressure in the nozzle chamber 2 results in an expansion of the meniscus 3 as illustrated in FIG. 2.
The actuators 8, 9 are activated only briefly and subsequently deactivated. Consequently, the situation is as illustrated in FIG. 3 with the actuators 8, 9 returning to their original positions. This results in a general inflow of ink back into the nozzle chamber 2 and a necking and breaking of the meniscus 3 resulting in the ejection of a drop 12. The necking and breaking of the meniscus 3 is a consequence of the forward momentum of the ink associated with drop 12 and the backward pressure experienced as a result of the return of the actuators 8, 9 to their original positions. The return of the actuators 8,9 also results in a general inflow of ink from the channel 6 as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in FIG. 1.
FIGS. 4(a) and 4(b) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material 14 having a high coefficient of thermal expansion. Embedded within the material 14 are a series of heater elements 15 which can be a series of conductive elements designed to carry a current. The conductive elements 15 are heated by passing a current through the elements 15 with the heating resulting in a general increase in temperature in the area around the heating elements 15. The position of the elements 15 is such that uneven heating of the material 14 occurs. The uneven increase in temperature causes a corresponding uneven expansion of the material 14. Hence, as illustrated in FIG. 4(b), the PTFE is bent generally in the direction shown.
In FIG. 5, there is illustrated a side perspective view of one embodiment of a nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber 2 is formed with an isotropic surface etch of the wafer 5. The wafer 5 can include a CMOS layer including all the required power and drive circuits. Further, the actuators 8, 9 each have a leaf or petal formation which extends towards a nozzle rim 28 defining the ejection port 4. The normally inner end of each leaf or petal formation is displaceable with respect to the nozzle rim 28. Each activator 8, 9 has an internal copper core 17 defining the element 15. The core 17 winds in a serpentine manner to provide for substantially unhindered expansion of the actuators 8, 9. The operation of the actuators 8, 9 is as illustrated in FIG. 4(a) and FIG. 4(b) such that, upon activation, the actuators 8 bend as previously described resulting in a displacement of each petal formation away from the nozzle rim 28 and into the nozzle chamber 2. The ink supply channel 6 can be created via a deep silicon back edge of the wafer 5 utilizing a plasma etcher or the like. The copper or aluminium core 17 can provide a complete circuit. A central arm 18 which can include both metal and PTFE portions provides the main structural support for the actuators 8, 9.
Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzle arrangement 1 in accordance with the principles of the preferred embodiment is shown. The nozzle arrangement 1 is preferably manufactured using microelectromechanical (MEMS) techniques and can include the following construction techniques:
As shown initially in FIG. 6, the initial processing starting material is a standard semi-conductor wafer 20 having a complete CMOS level 21 to a first level of metal. The first level of metal includes portions 22 which are utilized for providing power to the thermal actuators 8, 9.
The first step, as illustrated in FIG. 7, is to etch a nozzle region down to the silicon wafer 20 utilizing an appropriate mask.
Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to define vias 24 for interconnecting multiple levels.
Next, as illustrated in FIG. 9, the second level metal layer is deposited, masked and etched to define a heater structure 25. The heater structure 25 includes via 26 interconnected with a lower aluminium layer.
Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE is deposited and etched to the depth of 1 μm utilizing a nozzle rim mask to define the nozzle rim 28 in addition to ink flow guide rails 29 which generally restrain any wicking along the surface of the PTFE layer. The guide rails 29 surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation.
Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzle and actuator mask to define a port portion 30 and slots 31 and 32.
Next, as illustrated in FIG. 12, the wafer is crystallographically etched on a <111> plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber 33, directly below the port portion 30.
In FIG. 13, the ink supply channel 34 can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of United Kingdom. An array of ink jet nozzles can be formed simultaneously with a portion of an array 36 being illustrated in FIG. 14. A portion of the printhead is formed simultaneously and diced by the STS etching process. The array 36 shown provides for four column printing with each separate column attached to a different colour ink supply channel being supplied from the back of the wafer. Bond pads 37 provide for electrical control of the ejection mechanism.
In this manner, large pagewidth printheads can be fabricated so as to provide for a drop-on-demand ink ejection mechanism.
One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:
1. Using a double-sided polished wafer 60, complete a 0.5 micron, one poly, 2 metal CMOS process 61. This step is shown in FIG. 16. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 15 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Etch the CMOS oxide layers down to silicon or second level metal using Mask 1. This mask defines the nozzle cavity and the edge of the chips. This step is shown in FIG. 16.
3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence.
4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.
5. Etch the PTFE and CMOS oxide layers to second level metal using Mask 2. This mask defines the contact vias for the heater electrodes. This step is shown in FIG. 17.
6. Deposit and pattern 0.5 microns of gold 63 using a lift-off process using Mask 3. This mask defines the heater pattern. This step is shown in FIG. 18.
7. Deposit 1.5 microns of PTFE 64.
8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim 65 and the rim at the edge 66 of the nozzle chamber. This step is shown in FIG. 19.
9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask 5. This mask defines a gap 67 at inner edges of the actuators, and the edge of the chips. It also forms the mask for a subsequent crystallographic etch. This step is shown in FIG. 20.
10. Crystallographically etch the exposed silicon using KOH. This etch stops on <111> crystallographic planes 68, forming an inverted square pyramid with sidewall angles of 54.74 degrees. This step is shown in FIG. 21.
11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 6. This mask defines the ink inlets 69 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 22.
12. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets 69 at the back of the wafer.
13. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
14. Fill the completed print heads with ink 70 and test them. A filled nozzle is shown in FIG. 23.
The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.
It would 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 embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.
Ink Jet Technologies
The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. 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 (<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 below 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 above which matches the docket numbers in the table under the heading Cross References to Related Applications.
Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.
Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.
Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.
The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.










ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)












Description
Advantages
Disadvantages
Examples















Thermal
An electrothermal
Large force
High power
Canon


bubble
heater heats the
generated
Ink carrier
Bubblejet 1979



ink to above
Simple
limited to water
Endo et al GB



boiling point,
construction
Low
patent 2,007,162



transferring
No moving
efficiency
Xerox heater-



significant heat to
parts
High
in-pit 1990



the aqueous ink. A
Fast operation
temperatures
Hawkins et al



bubble nucleates
Small chip
required
U.S. Pat. No. 4,899,181



and quickly forms,
area required for
High
Hewlett-



expelling the ink.
actuator
mechanical
Packard TIJ



The efficiency of

stress
1982 Vaught et



the process is low,

Unusual
al U.S. Pat. No.



with typically less

materials
4,490,728



than 0.05% of the

required



electrical energy

Large drive



being transformed

transistors



into kinetic energy

Cavitation



of the drop.

causes actuator





failure





Kogation





reduces bubble





formation





Large print





heads are





difficult to





fabricate


Piezoelectric
A piezoelectric
Low power
Very large
Kyser et al



crystal such as
consumption
area required for
U.S. Pat. No. 3,946,398



lead lanthanum
Many ink
actuator
Zoltan U.S. Pat. No.



zirconate (PZT) is
types can be
Difficult to
3,683,212



electrically
used
integrate with
1973 Stemme



activated, and
Fast operation
electronics
U.S. Pat. No. 3,747,120



either expands,
High
High voltage
Epson Stylus



shears, or bends to
efficiency
drive transistors
Tektronix



apply pressure to

required
IJ04



the ink, ejecting

Full



drops.

pagewidth print





heads





impractical due





to actuator size





Requires





electrical poling





in high field





strengths during





manufacture


Electrostrictive
An electric field is
Low power
Low
Seiko Epson,



used to activate
consumption
maximum strain
Usui et all JP



electrostriction in
Many ink
(approx. 0.01%)
253401/96



relaxor materials
types can be
Large area
IJ04



such as lead
used
required for



lanthanum
Low thermal
actuator due to



zirconate titanate
expansion
low strain



(PLZT) or lead
Electric field
Response



magnesium
strength required
speed is



niobate (PMN).
(approx. 3.5 V/μm)
marginal (~10 μs)




can be
High voltage




generated
drive transistors




without
required




difficulty
Full




Does not
pagewidth print




require electrical
heads




poling
impractical due





to actuator size


Ferroelectric
An electric field is
Low power
Difficult to
IJ04



used to induce a
consumption
integrate with



phase transition
Many ink
electronics



between the
types can be
Unusual



antiferroelectric
used
materials such as



(AFE) and
Fast operation
PLZSnT are



ferroelectric (FE)
(<1 μs)
required



phase. Perovskite
Relatively
Actuators



materials such as
high longitudinal
require a large



tin modified lead
strain
area



lanthanum
High



zirconate titanate
efficiency



(PLZSnT) exhibit
Electric field



large strains of up
strength of



to 1% associated
around 3 V/μm



with the AFE to
can be readily



FE phase
provided



transition.


Electrostatic
Conductive plates
Low power
Difficult to
IJ02, IJ04


plates
are separated by a
consumption
operate



compressible or
Many ink
electrostatic



fluid dielectric
types can be
devices in an



(usually air). Upon
used
aqueous



application of a
Fast operation
environment



voltage, the plates

The



attract each other

electrostatic



and displace ink,

actuator will



causing drop

normally need to



ejection. The

be separated



conductive plates

from the ink



may be in a comb

Very large



or honeycomb

area required to



structure, or

achieve high



stacked to increase

forces



the surface area

High voltage



and therefore the

drive transistors



force.

may be required





Full





pagewidth print





heads are not





competitive due





to actuator size


Electrostatic
A strong electric
Low current
High voltage
1989 Saito et


pull
field is applied to
consumption
required
al, U.S. Pat. No.


on ink
the ink, whereupon
Low
May be
4,799,068



electrostatic
temperature
damaged by
1989 Miura et



attraction

sparks due to air
al, U.S. Pat. No.



accelerates the ink

breakdown
4,810,954



towards the print

Required field
Tone-jet



medium.

strength





increases as the





drop size





decreases





High voltage





drive transistors





required





Electrostatic





field attracts dust


Permanent
An electromagnet
Low power
Complex
IJ07, IJ10


magnet
directly attracts a
consumption
fabrication


electromagnetic
permanent magnet,
Many ink
Permanent



displacing ink and
types can be
magnetic



causing drop
used
material such as



ejection. Rare
Fast operation
Neodymium Iron



earth magnets with
High
Boron (NdFeB)



a field strength
efficiency
required.



around 1 Tesla can
Easy
High local



be used. Examples
extension from
currents required



are: Samarium
single nozzles to
Copper



Cobalt (SaCo) and
pagewidth print
metalization



magnetic materials
heads
should be used



in the neodymium

for long



iron boron family

electromigration



(NdFeB,

lifetime and low



NdDyFeBNb,

resistivity



NdDyFeB, etc)

Pigmented





inks are usually





infeasible





Operating





temperature





limited to the





Curie





temperature





(around 540 K)


Soft
A solenoid
Low power
Complex
IJ01, IJ05,


magnetic
induced a
consumption
fabrication
IJ08, IJ10, IJ12,


core
magnetic field in a
Many ink
Materials not
IJ14, IJ15, IJ17


electromagnetic
soft magnetic core
types can be
usually present



or yoke fabricated
used
in a CMOS fab



from a ferrous
Fast operation
such as NiFe,



material such as
High
CoNiFe, or CoFe



electroplated iron
efficiency
are required



alloys such as
Easy
High local



CoNiFe [1], CoFe,
extension from
currents required



or NiFe alloys.
single nozzles to
Copper



Typically, the soft
pagewidth print
metalization



magnetic material
heads
should be used



is in two parts,

for long



which are

electromigration



normally held

lifetime and low



apart by a spring.

resistivity



When the solenoid

Electroplating



is actuated, the two

is required



parts attract,

High



displacing the ink.

saturation flux





density is





required (2.0-2.1





T is achievable





with CoNiFe





[1])


Lorenz
The Lorenz force
Low power
Force acts as a
IJ06, IJ11,


force
acting on a current
consumption
twisting motion
IJ13, IJ16



carrying wire in a
Many ink
Typically,



magnetic field is
types can be
only a quarter of



utilized.
used
the solenoid



This allows the
Fast operation
length provides



magnetic field to
High
force in a useful



be supplied
efficiency
direction



externally to the
Easy
High local



print head, for
extension from
currents required



example with rare
single nozzles to
Copper



earth permanent
pagewidth print
metalization



magnets.
heads
should be used



Only the current

for long



carrying wire need

electromigration



be fabricated on

lifetime and low



the print-head,

resistivity



simplifying

Pigmented



materials

inks are usually



requirements.

infeasible


Magnetostriction
The actuator uses
Many ink
Force acts as a
Fischenbeck,



the giant
types can be
twisting motion
U.S. Pat. No. 4,032,929



magnetostrictive
used
Unusual
IJ25



effect of materials
Fast operation
materials such as



such as Terfenol-D
Easy
Terfenol-D are



(an alloy of
extension from
required



terbium,
single nozzles to
High local



dysprosium and
pagewidth print
currents required



iron developed at
heads
Copper



the Naval
High force is
metalization



Ordnance
available
should be used



Laboratory, hence

for long



Ter-Fe-NOL). For

electromigration



best efficiency, the

lifetime and low



actuator should be

resistivity



pre-stressed to

Pre-stressing



approx. 8 MPa.

may be required


Surface
Ink under positive
Low power
Requires
Silverbrook,


tension
pressure is held in
consumption
supplementary
EP 0771 658 A2


reduction
a nozzle by surface
Simple
force to effect
and related



tension. The
construction
drop separation
patent



surface tension of
No unusual
Requires
applications



the ink is reduced
materials
special ink



below the bubble
required in
surfactants



threshold, causing
fabrication
Speed may be



the ink to egress
High
limited by



from the nozzle.
efficiency
surfactant




Easy
properties




extension from




single nozzles to




pagewidth print




heads


Viscosity
The ink viscosity
Simple
Requires
Silverbrook,


reduction
is locally reduced
construction
supplementary
EP 0771 658 A2



to select which
No unusual
force to effect
and related



drops are to be
materials
drop separation
patent



ejected. A
required in
Requires
applications



viscosity reduction
fabrication
special ink



can be achieved
Easy
viscosity



electrothermally
extension from
properties



with most inks, but
single nozzles to
High speed is



special inks can be
pagewidth print
difficult to



engineered for a
heads
achieve



100:1 viscosity

Requires



reduction.

oscillating ink





pressure





A high





temperature





difference





(typically 80





degrees) is





required


Acoustic
An acoustic wave
Can operate
Complex
1993



is generated and
without a nozzle
drive circuitry
Hadimioglu et



focussed upon the
plate
Complex
al, EUP 550,192



drop ejection

fabrication
1993 Elrod et



region.

Low
al, EUP 572,220





efficiency





Poor control





of drop position





Poor control





of drop volume


Thermo-
An actuator which
Low power
Efficient
IJ03, IJ09,


elastic
relies upon
consumption
aqueous
IJ17, IJ18, IJ19,


bend
differential
Many ink
operation
IJ20, IJ21, IJ22,


actuator
thermal expansion
types can be
requires a
IJ23, IJ24, IJ27,



upon Joule heating
used
thermal insulator
IJ28, IJ29, IJ30,



is used.
Simple planar
on the hot side
IJ31, IJ32, IJ33,




fabrication
Corrosion
IJ34, IJ35, IJ36,




Small chip
prevention can
IJ37, IJ38, IJ39,




area required for
be difficult
IJ40, IJ41




each actuator
Pigmented




Fast operation
inks may be




High
infeasible, as




efficiency
pigment particles




CMOS
may jam the




compatible
bend actuator




voltages and




currents




Standard




MEMS




processes can be




used




Easy




extension from




single nozzles to




pagewidth print




heads


High CTE
A material with a
High force
Requires
IJ09, IJ17,


thermo-
very high
can be generated
special material
IJ18, IJ20, IJ21,


elastic
coefficient of
Three
(e.g. PTFE)
IJ22, IJ23, IJ24,


actuator
thermal expansion
methods of
Requires a
IJ27, IJ28, IJ29,



(CTE) such as
PTFE deposition
PTFE deposition
IJ30, IJ31, IJ42,



polytetrafluoroethylene
are under
process, which is
IJ43, IJ44



(PTFE) is
development:
not yet standard



used. As high CTE
chemical vapor
in ULSI fabs



materials are
deposition
PTFE



usually non-
(CVD), spin
deposition



conductive, a
coating, and
cannot be



heater fabricated
evaporation
followed with



from a conductive
PTFE is a
high temperature



material is
candidate for
(above 350° C.)



incorporated. A 50 μm
low dielectric
processing



long PTFE
constant
Pigmented



bend actuator with
insulation in
inks may be



polysilicon heater
ULSI
infeasible, as



and 15 mW power
Very low
pigment particles



input can provide
power
may jam the



180 μN force and
consumption
bend actuator



10 μm deflection.
Many ink



Actuator motions
types can be



include:
used



Bend
Simple planar



Push
fabrication



Buckle
Small chip



Rotate
area required for




each actuator




Fast operation




High




efficiency




CMOS




compatible




voltages and




currents




Easy




extension from




single nozzles to




pagewidth print




heads


Conductive
A polymer with a
High force
Requires
IJ24


polymer
high coefficient of
can be generated
special materials


thermo-
thermal expansion
Very low
development


elastic
(such as PTFE) is
power
(High CTE


actuator
doped with
consumption
conductive



conducting
Many ink
polymer)



substances to
types can be
Requires a



increase its
used
PTFE deposition



conductivity to
Simple planar
process, which is



about 3 orders of
fabrication
not yet standard



magnitude below
Small chip
in ULSI fabs



that of copper. The
area required for
PTFE



conducting
each actuator
deposition



polymer expands
Fast operation
cannot be



when resistively
High
followed with



heated.
efficiency
high temperature



Examples of
CMOS
(above 350° C.)



conducting
compatible
processing



dopants include:
voltages and
Evaporation



Carbon nanotubes
currents
and CVD



Metal fibers
Easy
deposition



Conductive
extension from
techniques



polymers such as
single nozzles to
cannot be used



doped
pagewidth print
Pigmented



polythiophene
heads
inks may be



Carbon granules

infeasible, as





pigment particles





may jam the





bend actuator


Shape
A shape memory
High force is
Fatigue limits
IJ26


memory
alloy such as TiNi
available
maximum


alloy
(also known as
(stresses of
number of cycles



Nitinol - Nickel
hundreds of
Low strain



Titanium alloy
MPa)
(1%) is required



developed at the
Large strain is
to extend fatigue



Naval Ordnance
available (more
resistance



Laboratory) is
than 3%)
Cycle rate



thermally switched
High
limited by heat



between its weak
corrosion
removal



martensitic state
resistance
Requires



and its high
Simple
unusual



stiffness austenic
construction
materials (TiNi)



state. The shape of
Easy
The latent



the actuator in its
extension from
heat of



martensitic state is
single nozzles to
transformation



deformed relative
pagewidth print
must be



to the austenic
heads
provided



shape. The shape
Low voltage
High current



change causes
operation
operation



ejection of a drop.

Requires pre-





stressing to





distort the





martensitic state


Linear
Linear magnetic
Linear
Requires
IJ12


Magnetic
actuators include
Magnetic
unusual


Actuator
the Linear
actuators can be
semiconductor



Induction Actuator
constructed with
materials such as



(LIA), Linear
high thrust, long
soft magnetic



Permanent Magnet
travel, and high
alloys (e.g.



Synchronous
efficiency using
CoNiFe)



Actuator
planar
Some varieties



(LPMSA), Linear
semiconductor
also require



Reluctance
fabrication
permanent



Synchronous
techniques
magnetic



Actuator (LRSA),
Long actuator
materials such as



Linear Switched
travel is
Neodymium iron



Reluctance
available
boron (NdFeB)



Actuator (LSRA),
Medium force
Requires



and the Linear
is available
complex multi-



Stepper Actuator
Low voltage
phase drive



(LSA).
operation
circuitry





High current





operation

























Description
Advantages
Disadvantages
Examples
















BASIC OPERATION MODE











Actuator
This is the
Simple
Drop
Thermal ink


directly
simplest mode of
operation
repetition rate is
jet


pushes
operation: the
No external
usually limited
Piezoelectric


ink
actuator directly
fields required
to around 10 kHz.
ink jet



supplies sufficient
Satellite drops
However,
IJ01, IJ02,



kinetic energy to
can be avoided if
this is not
IJ03, IJ04, IJ05,



expel the drop.
drop velocity is
fundamental to
IJ06, IJ07, IJ09,



The drop must
less than 4 m/s
the method, but
IJ11, IJ12, IJ14,



have a sufficient
Can be
is related to the
IJ16, IJ20, IJ22,



velocity to
efficient,
refill method
IJ23, IJ24, IJ25,



overcome the
depending upon
normally used
IJ26, IJ27, IJ28,



surface tension.
the actuator used
All of the drop
IJ29, IJ30, IJ31,





kinetic energy
IJ32, IJ33, IJ34,





must be
IJ35, IJ36, IJ37,





provided by the
IJ38, IJ39, IJ40,





actuator
IJ41, IJ42, IJ43,





Satellite drops
IJ44





usually form if





drop velocity is





greater than 4.5 m/s


Proximity
The drops to be
Very simple
Requires close
Silverbrook,



printed are
print head
proximity
EP 0771 658 A2



selected by some
fabrication can
between the
and related



manner (e.g.
be used
print head and
patent



thermally induced
The drop
the print media
applications



surface tension
selection means
or transfer roller



reduction of
does not need to
May require



pressurized ink).
provide the
two print heads



Selected drops are
energy required
printing alternate



separated from the
to separate the
rows of the



ink in the nozzle
drop from the
image



by contact with the
nozzle
Monolithic



print medium or a

color print heads



transfer roller.

are difficult


Electrostatic
The drops to be
Very simple
Requires very
Silverbrook,


pull
printed are
print head
high electrostatic
EP 0771 658 A2


on ink
selected by some
fabrication can
field
and related



manner (e.g.
be used
Electrostatic
patent



thermally induced
The drop
field for small
applications



surface tension
selection means
nozzle sizes is
Tone-Jet



reduction of
does not need to
above air



pressurized ink).
provide the
breakdown



Selected drops are
energy required
Electrostatic



separated from the
to separate the
field may attract



ink in the nozzle
drop from the
dust



by a strong electric
nozzle



field.


Magnetic
The drops to be
Very simple
Requires
Silverbrook,


pull on
printed are
print head
magnetic ink
EP 0771 658 A2


ink
selected by some
fabrication can
Ink colors
and related



manner (e.g.
be used
other than black
patent



thermally induced
The drop
are difficult
applications



surface tension
selection means
Requires very



reduction of
does not need to
high magnetic



pressurized ink).
provide the
fields



Selected drops are
energy required



separated from the
to separate the



ink in the nozzle
drop from the



by a strong
nozzle



magnetic field



acting on the



magnetic ink.


Shutter
The actuator
High speed
Moving parts
IJ13, IJ17,



moves a shutter to
(>50 kHz)
are required
IJ21



block ink flow to
operation can be
Requires ink



the nozzle. The ink
achieved due to
pressure



pressure is pulsed
reduced refill
modulator



at a multiple of the
time
Friction and



drop ejection
Drop timing
wear must be



frequency.
can be very
considered




accurate
Stiction is




The actuator
possible




energy can be




very low


Shuttered
The actuator
Actuators with
Moving parts
IJ08, IJ15,


grill
moves a shutter to
small travel can
are required
IJ18, IJ19



block ink flow
be used
Requires ink



through a grill to
Actuators with
pressure



the nozzle. The
small force can
modulator



shutter movement
be used
Friction and



need only be equal
High speed
wear must be



to the width of the
(>50 kHz)
considered



grill holes.
operation can be
Stiction is




achieved
possible


Pulsed
A pulsed magnetic
Extremely low
Requires an
IJ10


magnetic
field attracts an
energy operation
external pulsed


pull on
‘ink pusher’ at the
is possible
magnetic field


ink
drop ejection
No heat
Requires


pusher
frequency. An
dissipation
special materials



actuator controls a
problems
for both the



catch, which

actuator and the



prevents the ink

ink pusher



pusher from

Complex



moving when a

construction



drop is not to be



ejected.







AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)











None
The actuator
Simplicity of
Drop ejection
Most ink jets,



directly fires the
construction
energy must be
including



ink drop, and there
Simplicity of
supplied by
piezoelectric and



is no external field
operation
individual nozzle
thermal bubble.



or other
Small physical
actuator
IJ01, IJ02,



mechanism
size

IJ03, IJ04, IJ05,



required.


IJ07, IJ09, IJ11,






IJ12, IJ14, IJ20,






IJ22, IJ23, IJ24,






IJ25, IJ26, IJ27,






IJ28, IJ29, IJ30,






IJ31, IJ32, IJ33,






IJ34, IJ35, IJ36,






IJ37, IJ38, IJ39,






IJ40, IJ41, IJ42,






IJ43, IJ44







BASIC OPERATION MODE











Oscillating
The ink pressure
Oscillating ink
Requires
Silverbrook,


ink
oscillates,
pressure can
external ink
EP 0771 658 A2


pressure
providing much of
provide a refill
pressure
and related


(including
the drop ejection
pulse, allowing
oscillator
patent


acoustic
energy. The
higher operating
Ink pressure
applications


stimulation)
actuator selects
speed
phase and
IJ08, IJ13,



which drops are to
The actuators
amplitude must
IJ15, IJ17, IJ18,



be fired by
may operate
be carefully
IJ19, IJ21



selectively
with much lower
controlled



blocking or
energy
Acoustic



enabling nozzles.
Acoustic
reflections in the



The ink pressure
lenses can be
ink chamber



oscillation may be
used to focus the
must be



achieved by
sound on the
designed for



vibrating the print
nozzles



head, or preferably



by an actuator in



the ink supply.


Media
The print head is
Low power
Precision
Silverbrook,


proximity
placed in close
High accuracy
assembly
EP 0771 658 A2



proximity to the
Simple print
required
and related



print medium.
head
Paper fibers
patent



Selected drops
construction
may cause
applications



protrude from the

problems



print head further

Cannot print



than unselected

on rough



drops, and contact

substrates



the print medium.



The drop soaks



into the medium



fast enough to



cause drop



separation.


Transfer
Drops are printed
High accuracy
Bulky
Silverbrook,


roller
to a transfer roller
Wide range of
Expensive
EP 0771 658 A2



instead of straight
print substrates
Complex
and related



to the print
can be used
construction
patent



medium. A
Ink can be

applications



transfer roller can
dried on the

Tektronix hot



also be used for
transfer roller

melt



proximity drop


piezoelectric ink



separation.


jet






Any of the IJ






series


Electrostatic
An electric field is
Low power
Field strength
Silverbrook,



used to accelerate
Simple print
required for
EP 0771 658 A2



selected drops
head
separation of
and related



towards the print
construction
small drops is
patent



medium.

near or above air
applications





breakdown
Tone-Jet


Direct
A magnetic field is
Low power
Requires
Silverbrook,


magnetic
used to accelerate
Simple print
magnetic ink
EP 0771 658 A2


field
selected drops of
head
Requires
and related



magnetic ink
construction
strong magnetic
patent



towards the print

field
applications



medium.


Cross
The print head is
Does not
Requires
IJ06, IJ16


magnetic
placed in a
require magnetic
external magnet


field
constant magnetic
materials to be
Current



field. The Lorenz
integrated in the
densities may be



force in a current
print head
high, resulting in



carrying wire is
manufacturing
electromigration



used to move the
process
problems



actuator.


Pulsed
A pulsed magnetic
Very low
Complex print
IJ10


magnetic
field is used to
power operation
head


field
cyclically attract a
is possible
construction



paddle, which
Small print
Magnetic



pushes on the ink.
head size
materials



A small actuator

required in print



moves a catch,

head



which selectively



prevents the



paddle from



moving.



















ACTUATOR AMPLIFICATION OR MODIFICATION METHOD












Description
Advantages
Disadvantages
Examples















None
No actuator
Operational
Many actuator
Thermal



mechanical
simplicity
mechanisms
Bubble Ink jet



amplification is

have insufficient
IJ01, IJ02,



used. The actuator

travel, or
IJ06, IJ07, IJ16,



directly drives the

insufficient
IJ25, IJ26



drop ejection

force, to



process.

efficiently drive





the drop ejection





process


Differential
An actuator
Provides
High stresses
Piezoelectric


expansion
material expands
greater travel in
are involved
IJ03, IJ09,


bend
more on one side
a reduced print
Care must be
IJ17, IJ18, IJ19,


actuator
than on the other.
head area
taken that the
IJ20, IJ21, IJ22,



The expansion

materials do not
IJ23, IJ24, IJ27,



may be thermal,

delaminate
IJ29, IJ30, IJ31,



piezoelectric,

Residual bend
IJ32, IJ33, IJ34,



magnetostrictive,

resulting from
IJ35, IJ36, IJ37,



or other

high temperature
IJ38, IJ39, IJ42,



mechanism. The

or high stress
IJ43, IJ44



bend actuator

during formation



converts a high



force low travel



actuator



mechanism to high



travel, lower force



mechanism.


Transient
A trilayer bend
Very good
High stresses
IJ40, IJ41


bend
actuator where the
temperature
are involved


actuator
two outside layers
stability
Care must be



are identical. This
High speed, as
taken that the



cancels bend due
a new drop can
materials do not



to ambient
be fired before
delaminate



temperature and
heat dissipates



residual stress. The
Cancels



actuator only
residual stress of



responds to
formation



transient heating of



one side or the



other.


Reverse
The actuator loads
Better
Fabrication
IJ05, IJ11


spring
a spring. When the
coupling to the
complexity



actuator is turned
ink
High stress in



off, the spring

the spring



releases. This can



reverse the



force/distance



curve of the



actuator to make it



compatible with



the force/time



requirements of



the drop ejection.


Actuator
A series of thin
Increased
Increased
Some


stack
actuators are
travel
fabrication
piezoelectric ink



stacked. This can
Reduced drive
complexity
jets



be appropriate
voltage
Increased
IJ04



where actuators

possibility of



require high

short circuits due



electric field

to pinholes



strength, such as



electrostatic and



piezoelectric



actuators.


Multiple
Multiple smaller
Increases the
Actuator
IJ12, IJ13,


actuators
actuators are used
force available
forces may not
IJ18, IJ20, IJ22,



simultaneously to
from an actuator
add linearly,
IJ28, IJ42, IJ43



move the ink. Each
Multiple
reducing



actuator need
actuators can be
efficiency



provide only a
positioned to



portion of the
control ink flow



force required.
accurately


Linear
A linear spring is
Matches low
Requires print
IJ15


Spring
used to transform a
travel actuator
head area for the



motion with small
with higher
spring



travel and high
travel



force into a longer
requirements



travel, lower force
Non-contact



motion.
method of




motion




transformation


Coiled
A bend actuator is
Increases
Generally
IJ17, IJ21,


actuator
coiled to provide
travel
restricted to
IJ34, IJ35



greater travel in a
Reduces chip
planar



reduced chip area.
area
implementations




Planar
due to extreme




implementations
fabrication




are relatively
difficulty in




easy to fabricate.
other





orientations.


Flexure
A bend actuator
Simple means
Care must be
IJ10, IJ19,


bend
has a small region
of increasing
taken not to
IJ33


actuator
near the fixture
travel of a bend
exceed the



point, which flexes
actuator
elastic limit in



much more readily

the flexure area



than the remainder

Stress



of the actuator.

distribution is



The actuator

very uneven



flexing is

Difficult to



effectively

accurately model



converted from an

with finite



even coiling to an

element analysis



angular bend,



resulting in greater



travel of the



actuator tip.


Catch
The actuator
Very low
Complex
IJ10



controls a small
actuator energy
construction



catch. The catch
Very small
Requires



either enables or
actuator size
external force



disables movement

Unsuitable for



of an ink pusher

pigmented inks



that is controlled



in a bulk manner.


Gears
Gears can be used
Low force,
Moving parts
IJ13



to increase travel
low travel
are required



at the expense of
actuators can be
Several



duration. Circular
used
actuator cycles



gears, rack and
Can be
are required



pinion, ratchets,
fabricated using
More complex



and other gearing
standard surface
drive electronics



methods can be
MEMS
Complex



used.
processes
construction





Friction,





friction, and





wear are





possible


Buckle
A buckle plate can
Very fast
Must stay
S. Hirata et al,


plate
be used to change
movement
within elastic
“An Ink-jet



a slow actuator
achievable
limits of the
Head Using



into a fast motion.

materials for
Diaphragm



It can also convert

long device life
Microactuator”



a high force, low

High stresses
Proc. IEEE



travel actuator into

involved
MEMS, February



a high travel,

Generally
1996, pp 418-423.



medium force

high power
IJ18, IJ27



motion.

requirement


Tapered
A tapered
Linearizes the
Complex
IJ14


magnetic
magnetic pole can
magnetic
construction


pole
increase travel at
force/distance



the expense of
curve



force.


Lever
A lever and
Matches low
High stress
IJ32, IJ36,



fulcrum is used to
travel actuator
around the
IJ37



transform a motion
with higher
fulcrum



with small travel
travel



and high force into
requirements



a motion with
Fulcrum area



longer travel and
has no linear



lower force. The
movement, and



lever can also
can be used for a



reverse the
fluid seal



direction of travel.


Rotary
The actuator is
High
Complex
IJ28


impeller
connected to a
mechanical
construction



rotary impeller. A
advantage
Unsuitable for



small angular
The ratio of
pigmented inks



deflection of the
force to travel of



actuator results in
the actuator can



a rotation of the
be matched to



impeller vanes,
the nozzle



which push the ink
requirements by



against stationary
varying the



vanes and out of
number of



the nozzle.
impeller vanes


Acoustic
A refractive or
No moving
Large area
1993


lens
diffractive (e.g.
parts
required
Hadimioglu et



zone plate)

Only relevant
al, EUP 550,192



acoustic lens is

for acoustic ink
1993 Elrod et



used to concentrate

jets
al, EUP 572,220



sound waves.


Sharp
A sharp point is
Simple
Difficult to
Tone-jet


conductive
used to concentrate
construction
fabricate using


point
an electrostatic

standard VLSI



field.

processes for a





surface ejecting





ink-jet





Only relevant





for electrostatic





ink jets



















ACTUATOR MOTION












Description
Advantages
Disadvantages
Examples















Volume
The volume of the
Simple
High energy is
Hewlett-


expansion
actuator changes,
construction in
typically
Packard Thermal



pushing the ink in
the case of
required to
Ink jet



all directions.
thermal ink jet
achieve volume
Canon





expansion. This
Bubblejet





leads to thermal





stress, cavitation,





and kogation in





thermal ink jet





implementations


Linear,
The actuator
Efficient
High
IJ01, IJ02,


normal to
moves in a
coupling to ink
fabrication
IJ04, IJ07, IJ11,


chip
direction normal to
drops ejected
complexity may
IJ14


surface
the print head
normal to the
be required to



surface. The
surface
achieve



nozzle is typically

perpendicular



in the line of

motion



movement.


Parallel to
The actuator
Suitable for
Fabrication
IJ12, IJ13,


chip
moves parallel to
planar
complexity
IJ15, IJ33,, IJ34,


surface
the print head
fabrication
Friction
IJ35, IJ36



surface. Drop

Stiction



ejection may still



be normal to the



surface.


Membrane
An actuator with a
The effective
Fabrication
1982 Howkins


push
high force but
area of the
complexity
U.S. Pat. No. 4,459,601



small area is used
actuator
Actuator size



to push a stiff
becomes the
Difficulty of



membrane that is
membrane area
integration in a



in contact with the

VLSI process



ink.


Rotary
The actuator
Rotary levers
Device
IJ05, IJ08,



causes the rotation
may be used to
complexity
IJ13, IJ28



of some element,
increase travel
May have



such a grill or
Small chip
friction at a pivot



impeller
area
point




requirements


Bend
The actuator bends
A very small
Requires the
1970 Kyser et



when energized.
change in
actuator to be
al U.S. Pat. No.



This may be due to
dimensions can
made from at
3,946,398



differential
be converted to a
least two distinct
1973 Stemme



thermal expansion,
large motion.
layers, or to have
U.S. Pat. No. 3,747,120



piezoelectric

a thermal
IJ03, IJ09,



expansion,

difference across
IJ10, IJ19, IJ23,



magnetostriction,

the actuator
IJ24, IJ25, IJ29,



or other form of


IJ30, IJ31, IJ33,



relative


IJ34, IJ35



dimensional



change.


Swivel
The actuator
Allows
Inefficient
IJ06



swivels around a
operation where
coupling to the



central pivot. This
the net linear
ink motion



motion is suitable
force on the



where there are
paddle is zero



opposite forces
Small chip



applied to opposite
area



sides of the paddle,
requirements



e.g. Lorenz force.


Straighten
The actuator is
Can be used
Requires
IJ26, IJ32



normally bent, and
with shape
careful balance



straightens when
memory alloys
of stresses to



energized.
where the
ensure that the




austenic phase is
quiescent bend is




planar
accurate


Double
The actuator bends
One actuator
Difficult to
IJ36, IJ37,


bend
in one direction
can be used to
make the drops
IJ38



when one element
power two
ejected by both



is energized, and
nozzles.
bend directions



bends the other
Reduced chip
identical.



way when another
size.
A small



element is
Not sensitive
efficiency loss



energized.
to ambient
compared to




temperature
equivalent single





bend actuators.


Shear
Energizing the
Can increase
Not readily
1985 Fishbeck



actuator causes a
the effective
applicable to
U.S. Pat. No. 4,584,590



shear motion in the
travel of
other actuator



actuator material.
piezoelectric
mechanisms




actuators


Radial
The actuator
Relatively
High force
1970 Zoltan


constriction
squeezes an ink
easy to fabricate
required
U.S. Pat. No. 3,683,212



reservoir, forcing
single nozzles
Inefficient



ink from a
from glass
Difficult to



constricted nozzle.
tubing as
integrate with




macroscopic
VLSI processes




structures


Coil/
A coiled actuator
Easy to
Difficult to
IJ17, IJ21,


uncoil
uncoils or coils
fabricate as a
fabricate for
IJ34, IJ35



more tightly. The
planar VLSI
non-planar



motion of the free
process
devices



end of the actuator
Small area
Poor out-of-



ejects the ink.
required,
plane stiffness




therefore low




cost


Bow
The actuator bows
Can increase
Maximum
IJ16, IJ18,



(or buckles) in the
the speed of
travel is
IJ27



middle when
travel
constrained



energized.
Mechanically
High force




rigid
required


Push-Pull
Two actuators
The structure
Not readily
IJ18



control a shutter.
is pinned at both
suitable for ink



One actuator pulls
ends, so has a
jets which



the shutter, and the
high out-of-
directly push the



other pushes it.
plane rigidity
ink


Curl
A set of actuators
Good fluid
Design
IJ20, IJ42


inwards
curl inwards to
flow to the
complexity



reduce the volume
region behind



of ink that they
the actuator



enclose.
increases




efficiency


Curl
A set of actuators
Relatively
Relatively
IJ43


outwards
curl outwards,
simple
large chip area



pressurizing ink in
construction



a chamber



surrounding the



actuators, and



expelling ink from



a nozzle in the



chamber.


Iris
Multiple vanes
High
High
IJ22



enclose a volume
efficiency
fabrication



of ink. These
Small chip
complexity



simultaneously
area
Not suitable



rotate, reducing

for pigmented



the volume

inks



between the vanes.


Acoustic
The actuator
The actuator
Large area
1993


vibration
vibrates at a high
can be
required for
Hadimioglu et



frequency.
physically
efficient
al, EUP 550,192




distant from the
operation at
1993 Elrod et




ink
useful
al, EUP 572,220





frequencies





Acoustic





coupling and





crosstalk





Complex





drive circuitry





Poor control





of drop volume





and position


None
In various ink jet
No moving
Various other
Silverbrook,



designs the
parts
tradeoffs are
EP 0771 658 A2



actuator does not

required to
and related



move.

eliminate
patent





moving parts
applications






Tone-jet



















NOZZLE REFILL METHOD












Description
Advantages
Disadvantages
Examples















Surface
This is the normal
Fabrication
Low speed
Thermal ink


tension
way that ink jets
simplicity
Surface
jet



are refilled. After
Operational
tension force
Piezoelectric



the actuator is
simplicity
relatively small
ink jet



energized, it

compared to
IJ01-IJ07,



typically returns

actuator force
IJ10-IJ14, IJ16,



rapidly to its

Long refill
IJ20, IJ22-IJ45



normal position.

time usually



This rapid return

dominates the



sucks in air

total repetition



through the nozzle

rate



opening. The ink



surface tension at



the nozzle then



exerts a small



force restoring the



meniscus to a



minimum area.



This force refills



the nozzle.


Shuttered
Ink to the nozzle
High speed
Requires
IJ08, IJ13,


oscillating
chamber is
Low actuator
common ink
IJ15, IJ17, IJ18,


ink
provided at a
energy, as the
pressure
IJ19, IJ21


pressure
pressure that
actuator need
oscillator



oscillates at twice
only open or
May not be



the drop ejection
close the shutter,
suitable for



frequency. When a
instead of
pigmented inks



drop is to be
ejecting the ink



ejected, the shutter
drop



is opened for 3



half cycles: drop



ejection, actuator



return, and refill.



The shutter is then



closed to prevent



the nozzle



chamber emptying



during the next



negative pressure



cycle.


Refill
After the main
High speed, as
Requires two
IJ09


actuator
actuator has
the nozzle is
independent



ejected a drop a
actively refilled
actuators per



second (refill)

nozzle



actuator is



energized. The



refill actuator



pushes ink into the



nozzle chamber.



The refill actuator



returns slowly, to



prevent its return



from emptying the



chamber again.


Positive
The ink is held a
High refill
Surface spill
Silverbrook,


ink
slight positive
rate, therefore a
must be
EP 0771 658 A2


pressure
pressure. After the
high drop
prevented
and related



ink drop is ejected,
repetition rate is
Highly
patent



the nozzle
possible
hydrophobic
applications



chamber fills

print head
Alternative



quickly as surface

surfaces are
for:, IJ01-IJ07,



tension and ink

required
IJ10-IJ14, IJ16,



pressure both


IJ20, IJ22-IJ45



operate to refill the



nozzle.



















METHOD OF RESTRICTING BACK-FLOW THROUGH INLET












Description
Advantages
Disadvantages
Examples















Long inlet
The ink inlet
Design
Restricts refill
Thermal ink


channel
channel to the
simplicity
rate
jet



nozzle chamber is
Operational
May result in
Piezoelectric



made long and
simplicity
a relatively large
ink jet



relatively narrow,
Reduces
chip area
IJ42, IJ43



relying on viscous
crosstalk
Only partially



drag to reduce

effective



inlet back-flow.


Positive
The ink is under a
Drop selection
Requires a
Silverbrook,


ink
positive pressure,
and separation
method (such as
EP 0771 658 A2


pressure
so that in the
forces can be
a nozzle rim or
and related



quiescent state
reduced
effective
patent



some of the ink
Fast refill time
hydrophobizing,
applications



drop already

or both) to
Possible



protrudes from the

prevent flooding
operation of the



nozzle.

of the ejection
following: IJ01-IJ07,



This reduces the

surface of the
IJ09-IJ12,



pressure in the

print head.
IJ14, IJ16, IJ20,



nozzle chamber


IJ22,, IJ23-IJ34,



which is required


IJ36-IJ41, IJ44



to eject a certain



volume of ink. The



reduction in



chamber pressure



results in a



reduction in ink



pushed out through



the inlet.


Baffle
One or more
The refill rate
Design
HP Thermal



baffles are placed
is not as
complexity
Ink Jet



in the inlet ink
restricted as the
May increase
Tektronix



flow. When the
long inlet
fabrication
piezoelectric ink



actuator is
method.
complexity (e.g.
jet



energized, the
Reduces
Tektronix hot



rapid ink
crosstalk
melt



movement creates

Piezoelectric



eddies which

print heads).



restrict the flow



through the inlet.



The slower refill



process is



unrestricted, and



does not result in



eddies.


Flexible
In this method
Significantly
Not applicable
Canon


flap
recently disclosed
reduces back-
to most ink jet


restricts
by Canon, the
flow for edge-
configurations


inlet
expanding actuator
shooter thermal
Increased



(bubble) pushes on
ink jet devices
fabrication



a flexible flap that

complexity



restricts the inlet.

Inelastic





deformation of





polymer flap





results in creep





over extended





use


Inlet filter
A filter is located
Additional
Restricts refill
IJ04, IJ12,



between the ink
advantage of ink
rate
IJ24, IJ27, IJ29,



inlet and the
filtration
May result in
IJ30



nozzle chamber.
Ink filter may
complex



The filter has a
be fabricated
construction



multitude of small
with no



holes or slots,
additional



restricting ink
process steps



flow. The filter



also removes



particles which



may block the



nozzle.


Small
The ink inlet
Design
Restricts refill
IJ02, IJ37,


inlet
channel to the
simplicity
rate
IJ44


compared
nozzle chamber

May result in


to nozzle
has a substantially

a relatively large



smaller cross

chip area



section than that of

Only partially



the nozzle,

effective



resulting in easier



ink egress out of



the nozzle than out



of the inlet.


Inlet
A secondary
Increases
Requires
IJ09


shutter
actuator controls
speed of the ink-
separate refill



the position of a
jet print head
actuator and



shutter, closing off
operation
drive circuit



the ink inlet when



the main actuator



is energized.


The inlet
The method avoids
Back-flow
Requires
IJ01, IJ03,


is located
the problem of
problem is
careful design to
IJ05, IJ06, IJ07,


behind
inlet back-flow by
eliminated
minimize the
IJ10, IJ11, IJ14,


the ink-
arranging the ink-

negative
IJ16, IJ22, IJ23,


pushing
pushing surface of

pressure behind
IJ25, IJ28, IJ31,


surface
the actuator

the paddle
IJ32, IJ33, IJ34,



between the inlet


IJ35, IJ36, IJ39,



and the nozzle.


IJ40, IJ41


Part of
The actuator and a
Significant
Small increase
IJ07, IJ20,


the
wall of the ink
reductions in
in fabrication
IJ26, IJ38


actuator
chamber are
back-flow can be
complexity


moves to
arranged so that
achieved


shut off
the motion of the
Compact


the inlet
actuator closes off
designs possible



the inlet.


Nozzle
In some
Ink back-flow
None related
Silverbrook,


actuator
configurations of
problem is
to ink back-flow
EP 0771 658 A2


does not
ink jet, there is no
eliminated
on actuation
and related


result in
expansion or


patent


ink back-
movement of an


applications


flow
actuator which


Valve-jet



may cause ink


Tone-jet



back-flow through



the inlet.

























Description
Advantages
Disadvantages
Examples
















NOZZLE CLEARING METHOD











Normal
All of the nozzles
No added
May not be
Most ink jet


nozzle
are fired
complexity on
sufficient to
systems


firing
periodically,
the print head
displace dried
IJ01, IJ02,



before the ink has

ink
IJ03, IJ04, IJ05,



a chance to dry.


IJ06, IJ07, IJ09,



When not in use


IJ10, IJ11, IJ12,



the nozzles are


IJ14, IJ16, IJ20,



sealed (capped)


IJ22, IJ23, IJ24,



against air.


IJ25, IJ26, IJ27,



The nozzle firing


IJ28, IJ29, IJ30,



is usually


IJ31, IJ32, IJ33,



performed during a


IJ34, IJ36, IJ37,



special clearing


IJ38, IJ39, IJ40,,



cycle, after first


IJ41, IJ42, IJ43,



moving the print


IJ44,, IJ45



head to a cleaning



station.


Extra
In systems which
Can be highly
Requires
Silverbrook,


power to
heat the ink, but do
effective if the
higher drive
EP 0771 658 A2


ink heater
not boil it under
heater is
voltage for
and related



normal situations,
adjacent to the
clearing
patent



nozzle clearing can
nozzle
May require
applications



be achieved by

larger drive



over-powering the

transistors



heater and boiling



ink at the nozzle.


Rapid
The actuator is
Does not
Effectiveness
May be used


succession
fired in rapid
require extra
depends
with: IJ01, IJ02,


of
succession. In
drive circuits on
substantially
IJ03, IJ04, IJ05,


actuator
some
the print head
upon the
IJ06, IJ07, IJ09,


pulses
configurations, this
Can be readily
configuration of
IJ10, IJ11, IJ14,



may cause heat
controlled and
the ink jet nozzle
IJ16, IJ20, IJ22,



build-up at the
initiated by

IJ23, IJ24, IJ25,



nozzle which boils
digital logic

IJ27, IJ28, IJ29,



the ink, clearing


IJ30, IJ31, IJ32,



the nozzle. In other


IJ33, IJ34, IJ36,



situations, it may


IJ37, IJ38, IJ39,



cause sufficient


IJ40, IJ41, IJ42,



vibrations to


IJ43, IJ44, IJ45



dislodge clogged



nozzles.


Extra
Where an actuator
A simple
Not suitable
May be used


power to
is not normally
solution where
where there is a
with: IJ03, IJ09,


ink
driven to the limit
applicable
hard limit to
IJ16, IJ20, IJ23,


pushing
of its motion,

actuator
IJ24, IJ25, IJ27,


actuator
nozzle clearing

movement
IJ29, IJ30, IJ31,



may be assisted by


IJ32, IJ39, IJ40,



providing an


IJ41, IJ42, IJ43,



enhanced drive


IJ44, IJ45



signal to the



actuator.


Acoustic
An ultrasonic
A high nozzle
High
IJ08, IJ13,


resonance
wave is applied to
clearing
implementation
IJ15, IJ17, IJ18,



the ink chamber.
capability can be
cost if system
IJ19, IJ21



This wave is of an
achieved
does not already



appropriate
May be
include an



amplitude and
implemented at
acoustic actuator



frequency to cause
very low cost in



sufficient force at
systems which



the nozzle to clear
already include



blockages. This is
acoustic



easiest to achieve
actuators



if the ultrasonic



wave is at a



resonant frequency



of the ink cavity.


Nozzle
A microfabricated
Can clear
Accurate
Silverbrook,


clearing
plate is pushed
severely clogged
mechanical
EP 0771 658 A2


plate
against the
nozzles
alignment is
and related



nozzles. The plate

required
patent



has a post for

Moving parts
applications



every nozzle. A

are required



post moves

There is risk



through each

of damage to the



nozzle, displacing

nozzles



dried ink.

Accurate





fabrication is





required


Ink
The pressure of the
May be
Requires
May be used


pressure
ink is temporarily
effective where
pressure pump
with all IJ series


pulse
increased so that
other methods
or other pressure
ink jets



ink streams from
cannot be used
actuator



all of the nozzles.

Expensive



This may be used

Wasteful of



in conjunction

ink



with actuator



energizing.


Print
A flexible ‘blade’
Effective for
Difficult to
Many ink jet


head
is wiped across the
planar print head
use if print head
systems


wiper
print head surface.
surfaces
surface is non-



The blade is
Low cost
planar or very



usually fabricated

fragile



from a flexible

Requires



polymer, e.g.

mechanical parts



rubber or synthetic

Blade can



elastomer.

wear out in high





volume print





systems


Separate
A separate heater
Can be
Fabrication
Can be used


ink
is provided at the
effective where
complexity
with many IJ


boiling
nozzle although
other nozzle

series ink jets


heater
the normal drop e-
clearing methods



ection mechanism
cannot be used



does not require it.
Can be



The heaters do not
implemented at



require individual
no additional



drive circuits, as
cost in some ink



many nozzles can
jet



be cleared
configurations



simultaneously,



and no imaging is



required.







NOZZLE PLATE CONSTRUCTION











Electroformed
A nozzle plate is
Fabrication
High
Hewlett


nickel
separately
simplicity
temperatures and
Packard Thermal



fabricated from

pressures are
Ink jet



electroformed

required to bond



nickel, and bonded

nozzle plate



to the print head

Minimum



chip.

thickness





constraints





Differential





thermal





expansion


Laser
Individual nozzle
No masks
Each hole
Canon


ablated or
holes are ablated
required
must be
Bubblejet


drilled
by an intense UV
Can be quite
individually
1988 Sercel et


polymer
laser in a nozzle
fast
formed
al., SPIE, Vol.



plate, which is
Some control
Special
998 Excimer



typically a
over nozzle
equipment
Beam



polymer such as
profile is
required
Applications, pp.



polyimide or
possible
Slow where
76-83



polysulphone
Equipment
there are many
1993




required is
thousands of
Watanabe et al.,




relatively low
nozzles per print
U.S. Pat. No. 5,208,604




cost
head





May produce





thin burrs at exit





holes


Silicon
A separate nozzle
High accuracy
Two part
K. Bean,


micromachined
plate is
is attainable
construction
IEEE



micromachined

High cost
Transactions on



from single crystal

Requires
Electron



silicon, and

precision
Devices, Vol.



bonded to the print

alignment
ED-25, No. 10,



head wafer.

Nozzles may
1978, pp 1185-1195





be clogged by
Xerox 1990





adhesive
Hawkins et al.,






U.S. Pat. No. 4,899,181


Glass
Fine glass
No expensive
Very small
1970 Zoltan


capillaries
capillaries are
equipment
nozzle sizes are
U.S. Pat. No. 3,683,212



drawn from glass
required
difficult to form



tubing. This
Simple to
Not suited for



method has been
make single
mass production



used for making
nozzles



individual nozzles,



but is difficult to



use for bulk



manufacturing of



print heads with



thousands of



nozzles.


Monolithic,
The nozzle plate is
High accuracy
Requires
Silverbrook,


surface
deposited as a
(<1 μm)
sacrificial layer
EP 0771 658 A2


micromachined
layer using
Monolithic
under the nozzle
and related


using
standard VLSI
Low cost
plate to form the
patent


VLSI
deposition
Existing
nozzle chamber
applications


lithographic
techniques.
processes can be
Surface may
IJ01, IJ02,


processes
Nozzles are etched
used
be fragile to the
IJ04, IJ11, IJ12,



in the nozzle plate

touch
IJ17, IJ18, IJ20,



using VLSI


IJ22, IJ24, IJ27,



lithography and


IJ28, IJ29, IJ30,



etching.


IJ31, IJ32, IJ33,






IJ34, IJ36, IJ37,






IJ38, IJ39, IJ40,






IJ41, IJ42, IJ43,






IJ44


Monolithic,
The nozzle plate is
High accuracy
Requires long
IJ03, IJ05,


etched
a buried etch stop
(<1 μm)
etch times
IJ06, IJ07, IJ08,


through
in the wafer.
Monolithic
Requires a
IJ09, IJ10, IJ13,


substrate
Nozzle chambers
Low cost
support wafer
IJ14, IJ15, IJ16,



are etched in the
No differential

IJ19, IJ21, IJ23,



front of the wafer,
expansion

IJ25, IJ26



and the wafer is



thinned from the



back side. Nozzles



are then etched in



the etch stop layer.


No nozzle
Various methods
No nozzles to
Difficult to
Ricoh 1995


plate
have been tried to
become clogged
control drop
Sekiya et al U.S. Pat. No.



eliminate the

position
5,412,413



nozzles entirely, to

accurately
1993



prevent nozzle

Crosstalk
Hadimioglu et al



clogging. These

problems
EUP 550,192



include thermal


1993 Elrod et



bubble


al EUP 572,220



mechanisms and



acoustic lens



mechanisms


Trough
Each drop ejector
Reduced
Drop firing
IJ35



has a trough
manufacturing
direction is



through which a
complexity
sensitive to



paddle moves.
Monolithic
wicking.



There is no nozzle



plate.


Nozzle slit
The elimination of
No nozzles to
Difficult to
1989 Saito et


instead of
nozzle holes and
become clogged
control drop
al U.S. Pat. No.


individual
replacement by a

position
4,799,068


nozzles
slit encompassing

accurately



many actuator

Crosstalk



positions reduces

problems



nozzle clogging,



but increases



crosstalk due to



ink surface waves



















DROP EJECTION DIRECTION












Description
Advantages
Disadvantages
Examples















Edge
Ink flow is along
Simple
Nozzles
Canon


(‘edge
the surface of the
construction
limited to edge
Bubblejet 1979


shooter’)
chip, and ink drops
No silicon
High
Endo et al GB



are ejected from
etching required
resolution is
patent 2,007,162



the chip edge.
Good heat
difficult
Xerox heater-




sinking via
Fast color
in-pit 1990




substrate
printing requires
Hawkins et al




Mechanically
one print head
U.S. Pat. No. 4,899,181




strong
per color
Tone-jet




Ease of chip




handing


Surface
Ink flow is along
No bulk
Maximum ink
Hewlett-


(‘roof
the surface of the
silicon etching
flow is severely
Packard TIJ


shooter’)
chip, and ink drops
required
restricted
1982 Vaught et



are ejected from
Silicon can

al U.S. Pat. No.



the chip surface,
make an

4,490,728



normal to the
effective heat

IJ02, IJ11,



plane of the chip.
sink

IJ12, IJ20, IJ22




Mechanical




strength


Through
Ink flow is through
High ink flow
Requires bulk
Silverbrook,


chip,
the chip, and ink
Suitable for
silicon etching
EP 0771 658 A2


forward
drops are ejected
pagewidth print

and related


(‘up
from the front
heads

patent


shooter’)
surface of the chip.
High nozzle

applications




packing density

IJ04, IJ17,




therefore low

IJ18, IJ24, IJ27-IJ45




manufacturing




cost


Through
Ink flow is through
High ink flow
Requires
IJ01, IJ03,


chip,
the chip, and ink
Suitable for
wafer thinning
IJ05, IJ06, IJ07,


reverse
drops are ejected
pagewidth print
Requires
IJ08, IJ09, IJ10,


(‘down
from the rear
heads
special handling
IJ13, IJ14, IJ15,


shooter’)
surface of the chip.
High nozzle
during
IJ16, IJ19, IJ21,




packing density
manufacture
IJ23, IJ25, IJ26




therefore low




manufacturing




cost


Through
Ink flow is through
Suitable for
Pagewidth
Epson Stylus


actuator
the actuator, which
piezoelectric
print heads
Tektronix hot



is not fabricated as
print heads
require several
melt



part of the same

thousand
piezoelectric ink



substrate as the

connections to
jets



drive transistors.

drive circuits





Cannot be





manufactured in





standard CMOS





fabs





Complex





assembly





required



















INK TYPE












Description
Advantages
Disadvantages
Examples















Aqueous,
Water based ink
Environmentally
Slow drying
Most existing


dye
which typically
friendly
Corrosive
ink jets



contains: water,
No odor
Bleeds on
All IJ series



dye, surfactant,

paper
ink jets



humectant, and

May
Silverbrook,



biocide.

strikethrough
EP 0771 658 A2



Modern ink dyes

Cockles paper
and related



have high water-


patent



fastness, light


applications



fastness


Aqueous,
Water based ink
Environmentally
Slow drying
IJ02, IJ04,


pigment
which typically
friendly
Corrosive
IJ21, IJ26, IJ27,



contains: water,
No odor
Pigment may
IJ30



pigment,
Reduced bleed
clog nozzles
Silverbrook,



surfactant,
Reduced
Pigment may
EP 0771 658 A2



humectant, and
wicking
clog actuator
and related



biocide.
Reduced
mechanisms
patent



Pigments have an
strikethrough
Cockles paper
applications



advantage in


Piezoelectric



reduced bleed,


ink-jets



wicking and


Thermal ink



strikethrough.


jets (with






significant






restrictions)


Methyl
MEK is a highly
Very fast
Odorous
All IJ series


Ethyl
volatile solvent
drying
Flammable
ink jets


Ketone
used for industrial
Prints on


(MEK)
printing on
various



difficult surfaces
substrates such



such as aluminum
as metals and



cans.
plastics


Alcohol
Alcohol based inks
Fast drying
Slight odor
All IJ series


(ethanol,
can be used where
Operates at
Flammable
ink jets


2-butanol,
the printer must
sub-freezing


and
operate at
temperatures


others)
temperatures
Reduced



below the freezing
paper cockle



point of water. An
Low cost



example of this is



in-camera



consumer



photographic



printing.


Phase
The ink is solid at
No drying
High viscosity
Tektronix hot


change
room temperature,
time-ink
Printed ink
melt


(hot melt)
and is melted in
instantly freezes
typically has a
piezoelectric ink



the print head
on the print
‘waxy’ feel
jets



before jetting. Hot
medium
Printed pages
1989 Nowak



melt inks are
Almost any
may ‘block’
U.S. Pat. No. 4,820,346



usually wax based,
print medium
Ink
All IJ series



with a melting
can be used
temperature may
ink jets



point around 80° C.
No paper
be above the



After jetting
cockle occurs
curie point of



the ink freezes
No wicking
permanent



almost instantly
occurs
magnets



upon contacting
No bleed
Ink heaters



the print medium
occurs
consume power



or a transfer roller.
No
Long warm-




strikethrough
up time




occurs


Oil
Oil based inks are
High
High
All IJ series



extensively used in
solubility
viscosity: this is
ink jets



offset printing,
medium for
a significant



They have
some dyes
limitation for use



advantages in
Does not
in ink jets, which



improved
cockle paper
usually require a



characteristics on
Does not wick
low viscosity.



paper (especially
through paper
Some short



no wicking or

chain and multi-



cockle). Oil

branched oils



soluble dies and

have a



pigments are

sufficiently low



required.

viscosity.





Slow drying


Microemulsion
A microemulsion
Stops ink
Viscosity
All IJ series



is a stable, self
bleed
higher than
ink jets



forming emulsion
High dye
water



of oil, water, and
solubility
Cost is



surfactant. The
Water, oil,
slightly higher



characteristic drop
and amphiphilic
than water based



size is less than
soluble dies can
ink



100 nm, and is
be used
High



determined by the
Can stabilize
surfactant



preferred curvature
pigment
concentration



of the surfactant.
suspensions
required (around





5%)

## Claims

1. A printhead for an inkjet printer, the printhead comprising a two-dimensional array of inkjet nozzle arrangements, each nozzle arrangement comprising:
a wafer portion defining both a nozzle chamber for storing ink and an ink supply channel in fluid communication with the nozzle chamber; and
a cover which covers the nozzle chamber and defines a nozzle rim from which a plurality of supports extends outwardly, the cover having a plurality of actuators extending inwardly toward the nozzle rim between respective pairs of adjacent supports and terminating in free ends, the actuators having internal heating elements which can be actuated so that the free ends reciprocate into and out of the nozzle chamber to eject ink out through the nozzle rim.

2. A printhead as claimed in claim 1, wherein the heating elements are serpentine.

3. A printhead as claimed in claim 2, wherein the heating elements are serially connected together.

4. A printhead as claimed in claim 1, wherein each nozzle chamber tapers inwardly towards the ink supply channel.

5. A printhead as claimed in claim 1, wherein each actuator has a polytetrafluoroethylene (PTFE) layer and an associated heater element embedded in the (PTFE) layer.

6. A printhead as claimed in claim 1, wherein each actuator has a petal formation extending toward the nozzle rim.

7. A printhead as claimed in claim 1, wherein the ink supply channel is in alignment with the nozzle rim.