Fluid ejection chip that incorporates wall-mounted actuators

Description

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation application U.S. application Ser. No. 09/855,093 filed May 14, 2001, now U.S. Pat. No. 6,505,912, which is a Continuation Application of U.S. application Ser. No. 09/112,806, filed Jul. 10, 1998, now granted U.S. Pat. No. 6,247,790.

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patents/patent applications identified by their US patent/patent application serial numbers are listed alongside the Australian applications from which the US patents/patent applications claim the right of priority.

Cross-	U.S. Patent/
Referenced	Patent Application
Australian	(Claiming Right
Provisional	of Priority from
Patent	Australian Provisional
Application No.	Application)	Docket No.

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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 fluid ejection and, in particular, discloses a fluid ejection chip.

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. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilizing the electro-thermal actuator.

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.

Applicant has developed a substantial amount of technology in the field of micro-electromechanical inkjet printing. The parent application is indeed directed to a particular aspect in this field. In this application, the Applicant has applied the technology to the more general field of fluid ejection.

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 center 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-electromechanical 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.

In this application, the invention extends to a fluid ejection chip that comprises

a substrate; and

a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising

• • a nozzle chamber defining structure which defines a nozzle chamber and which includes a wall in which a fluid ejection port is defined; and
  • at least one actuator for ejecting fluid from the nozzle chamber through the fluid ejection port, the, or each, actuator being displaceable with respect to the substrate on receipt of an electrical signal, wherein
  • the, or each, actuator is formed in said wall of the nozzle chamber defining structure, so that displacement of the, or each, actuator results in a change in volume of the nozzle chamber so that fluid is ejected from the fluid ejection port.

Each nozzle arrangement may include a plurality of actuators, each actuator including an actuating portion and a paddle positioned on the actuating portion, the actuating portion being anchored to the substrate and being displaceable on receipt of an electrical signal to displace the paddle, in turn, the paddles and the wall being substantially coplanar and the actuating portions being configured so that, upon receipt of said electrical signal, the actuating portions displace the paddles into the nozzle chamber to reduce a volume of the nozzle chamber, thereby ejecting fluid from the fluid ejection port.

A periphery of each paddle may be shaped to define a fluidic seal when the nozzle chamber is filled with fluid.

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 following description, reference is made to the ejection of ink for application to ink jet printing. However, it will readily be appreciated that the present application can be applied to any situation where fluid ejection is required.

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 aluminum 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 micro-electromechanical (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 aluminum 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 color 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 is set out in the following tables.

	Description	Advantages	Disadvantages	Examples

ACTUATOR MECHANISM

(APPLIED ONLY TO SELECTED INK DROPS)

Thermal	An electro-	Large force	High power	Canon
bubble	thermal heater	generated	Ink carrier	Bubblejet
	heats the ink to	Simple	limited to water	1979 Endo
	above boiling	construction	Low efficiency	et al GB
	point,	No moving	High	patent
	transferring	parts	temperatures	2,007,162
	significant heat	Fast	required	Xerox
	to the aqueous	operation	High	heater-in-pit
	ink. A bubble	Small chip	mechanical	1990
	nucleates and	area required	stress	Hawkins
	quickly forms,	for actuator	Unusual	et al
	expelling the		materials	U.S. Pat No.
	ink.		required	4,899,181
	The efficiency		Large drive	Hewlett-
	of the process		transistors	Packard TIJ
	is low, with		Cavitation	1982 Vaught
	typically less		causes actuator	et al
	than 0.05% of		failure	U.S. Pat No.
	the electrical		Kogation	4,490,728
	energy being		reduces
	transformed		bubble
	into kinetic		formation
	energy of the		Large print
	drop.		heads are
			difficult to
			fabricate
Piezo-	A piezoelectric	Low power	Very large area	Kyser et al
electric	crystal such as	consumption	required for	U.S. Pat No.
	lead lanthanum	Many ink	actuator	3,946,398
	zirconate (PZT)	types can be	Difficult to	Zoltan
	is electrically	used	integrate with	U.S. Pat No.
	activated, and	Fast	electronics	3,683,212
	either expands,	operation	High voltage	1973
	shears, or	High	drive	Stemme
	bends to apply	efficiency	transistors	U.S. Pat No.
	pressure to the		required	3,747,120
	ink, ejecting		Full pagewidth	Epson Stylus
	drops.		print heads	Tektronix
			to actuator size	IJ04
			Requires
			electrical
			poling in high
			field strengths
			during
			manufacture
			Requires
			electrical
			poling in high
			field strengths
			during
			manufacture
Electro-	An electric	Low power	Low maximum	Seiko Epson,
strictive	field is used to	consumption	strain (approx.	Usui et all JP
	activate	Many ink	0.01%)	253401/96
	electrostriction	types can	Large area	IJ04
	in relaxor	be used	required for
	materials such	Low thermal	actuator due to
	as lead	expansion	low strain
	lanthanum	Electric field	Response speed
	zirconate	strength	is marginal
	titanate (PLZT)	required	(~10 μs)
	or lead	(approx.	High voltage
	magnesium	3.5 V/μm)	drive
	niobate (PMN).	can be	transistors
		generated	required
		without	Full pagewidth
		difficulty	print heads
		Does not	impractical due
		require	to actuator size
		electrical
		poling
Ferro-	An electric	Low power	Difficult to	IJ04
electric	field is used to	consumption	integrate with
	induce a phase	Many ink	electronics
	transition	types can	Unusual
	between the	be used	materials such
	antiferroelectric	Fast	as PLZSnT are
	(AFE) and	operation	required
	ferroelectric	(<1 μs)	Actuators
	(FE) phase.	Relatively	require a
	Perovskite	high	large area
	materials such	longitudinal
	as tin modified	strain
	lead lanthanum	High
	zirconate	efficiency
	titanate	Electric
	(PLZSnT)	field
	exhibit large	strength of
	strains of up to	around 3
	1% associated	V/μm can
	with the AFE	be readily
	to FE phase	provided
	transition.
Electro-	Conductive	Low power	Difficult to	IJ02, IJ04
static	plates are	consumption	operate
plates	separated by a	Many ink	electrostatic
	compressible or	types can	devices in an
	fluid dielectric	be used	aqueous
	(usually air).	Fast	environment
	Upon	operation	The electro-
	application of a		static actuator
	voltage, the		will normally
	plates attract		need to be
	each other and		separated from
	displace ink,		the ink
	causing drop		Very large area
	ejection. The		required to
	conductive		achieve high
	plates may be		forces
	in a comb or		High voltage
	honeycomb		drive
	structure, or		transistors may
	stacked to		be required
	increase the		Full pagewidth
	surface area		print heads are
	and therefore		not competitive
	the force.		due to actuator
			size
Electro-	A strong	Low current	High voltage	1989 Saito
static	electric field is	consumption	required	et al,
pull on	applied to the	Low	May be	U.S. Pat No.
ink	ink, whereupon	temperature	damaged by	4,799,068
	electrostatic		sparks due to	1989 Miura
	attraction		air breakdown	et al,
	accelerates the		Required field	U.S. Pat No.
	ink towards the		strength	4,810,954
	print medium.		increases as the	Tone-jet
			drop size
			decreases
			High voltage
			drive
			transistors
			required
			Electrostatic
			field attracts
			dust
Permanent	An electro-	Low power	Complex	IJ07, IJ10
magnet	magnet directly	consumption	fabrication
electro-	attracts a	Many ink	Permanent
magnetic	permanent	types can	magnetic
	magnet,	be used	material such
	displacing ink	Fast	as Neodymium
	and causing	operation	Iron Boron
	drop ejection.	High	(NdFeB)
	Rare earth	efficiency	required.
	magnets with a	Easy	High local
	field strength	extension	currents
	around 1 Tesla	from single	required
	can be used.	nozzles to	Copper
	Examples are:	pagewidth	metalization
	Samarium	print heads	should be used
	Cobalt (SaCo)		for long
	and magnetic		electro-
	materials in the		migration
	neodymium		lifetime and
	iron boron		low resistivity
	family (NdFeB,		Pigmented inks
	NdDyFeBNb,		are usually
	NdDyFeB, etc)		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,
core	magnetic field	Many ink	Materials not	IJ12, IJ14,
electro-	in a soft	types can	usually present	IJ15, IJ17
magnetic	magnetic core	be used	in a CMOS fab
	or yoke	Fast	such as NiFe,
	fabricated from	operation	CoNiFe, or
	a ferrous	High	CoFe are
	material such	efficiency	required
	as electroplated	Easy	High local
	iron alloys such	extension	currents
	as CoNiFe [1],	from single	required
	CoFe, or NiFe	nozzles to	Copper
	alloys.	pagewidth	metalization
	Typically, the	print heads	should be used
	soft magnetic		for long
	material is in		electro-
	two parts,		migration
	which are		lifetime and
	normally held		low resistivity
	apart by a		Electroplating
	spring.		is required
	When the		High saturation
	solenoid is		flux density is
	actuated, the		required
	two parts		(2.0-2.1 T is
	attract,		achievable with
	displacing the		CoNiFe [1])
	ink.
Lorenz	The Lorenz	Low power	Force acts as a	IJ06, IJ11,
force	force acting on	consumption	twisting motion	IJ13, IJ16
	a current	Many ink	Typically, only
	carrying wire	types can	a quarter of the
	in a magnetic	be used	solenoid length
	field is utilized.	Fast	provides force
	This allows the	operation	in a useful
	magnetic field	High	direction
	to be supplied	efficiency	High local
	externally to	Easy	currents
	the print head,	extension	required
	for example	from single	Copper
	with rare earth	nozzles to	metalization
	permanent	pagewidth	should be used
	magnets.	print heads	for long
	Only the		electro-
	current		migration
	carrying wire		lifetime and
	need be		low resistivity
	fabricated on		Pigmented inks
	the print head,		are usually
	simplifying		infeasible
	materials
	requirements.
Magneto-	The actuator	Many ink	Force acts as a	Fischenbeck,
striction	uses the giant	types can	twisting motion	U.S. Pat No.
	magneto-	be used	Unusual	4,032,929
	strictive effect	Fast	materials such	IJ25
	of materials	operation	as Terfenol-D
	such as	Easy	are required
	Terfenol-D (an	extension	High local
	alloy of	from single	currents
	terbium,	nozzles to	required
	dysprosium and	pagewidth	Copper
	iron developed	print heads	metalization
	at the Naval	High force is	should be used
	Ordnance	available	for long
	Laboratory,		electro-
	hence		migration
	Ter-Fe-NOL).		lifetime and
	For best		low resistivity
	efficiency, the		Pre-stressing
	actuator should		may be
	be pre-stressed		required
	to approx.
	8 MPa.
Surface	Ink under	Low power	Requires	Silverbrook,
tension	positive	consumption	supplementary	EP 0771 658
reduction	pressure is held	Simple	force to effect	A2 and
	in a nozzle by	construction	drop separation	related
	surface tension.	No unusual	Requires	patent
	The surface	materials	special ink	applications
	tension of the	required in	surfactants
	ink is reduced	fabrication	Speed may be
	below the	High	limited by
	bubble	efficiency	surfactant
	threshold,	Easy	properties
	causing the ink	extension
	to egress from	from single
	the nozzle.	nozzles to
		pagewidth
		print heads
Viscosity	The ink	Simple	Requires	Silverbrook,
reduction	viscosity is	construction	supplementary	EP 0771 658
	locally reduced	No unusual	force to effect	A2 and
	to select which	materials	drop separation	related
	drops are to be	required in	Requires	patent
	ejected. A	fabrication	special ink	applications
	viscosity	Easy	viscosity
	reduction can	extension	properties
	be achieved	from single	High speed is
	electro-	nozzles to	difficult to
	thermally with	pagewidth	achieve
	most inks, but	print heads	Requires
	special inks can		oscillating
	be engineered		ink pressure
	for a 100:1		A high
	viscosity		temperature
	reduction.		difference
			(typically
			80 degrees) is
			required
Acoustic	An acoustic	Can operate	Complex drive	1993
	wave is	without a	circuitry	Hadimioglu
	generated and	nozzle plate	Complex	et al, EUP
	focussed upon		fabrication	550,192
	the drop		Low	1993 Elrod
	ejection region.		efficiency	et al, EUP
			Poor control of	572,220
			drop position
			Poor control of
			drop volume
Thermo-	An actuator	Low power	Efficient	IJ03, IJ09,
elastic	which relies	consumption	aqueous	IJ17, IJ18,
bend	upon	Many ink	operation	IJ19, IJ20,
actuator	differential	types can	requires a	IJ21, IJ22,
	thermal	be used	thermal	IJ23, IJ24,
	expansion upon	Simple	insulator on the	IJ27, IJ28,
	Joule heating	planar	hot side	IJ29, IJ30,
	is used.	fabrication	Corrosion	IJ31, IJ32,
		Small chip	prevention can	IJ33, IJ34,
		area required	be difficult	IJ35, IJ36,
		for each	Pigmented inks	IJ37, IJ38,
		actuator	may be	IJ39, IJ40,
		Fast	infeasible, as	IJ41
		operation	pigment
		High	particles may
		efficiency	jam the bend
		CMOS	actuator
		compatible
		voltages and
		currents
		Standard
		MEMS
		processes
		can be
		used
		Easy
		extension
		from single
		nozzles to
		pagewidth
		print heads
High CTE	A material with	High force	Requires	IJ09, IJ17,
thermo-	a very high	can be	special material	IJ18, IJ20,
elastic	coefficient of	generated	(e.g. PTFE)	IJ21, IJ22,
actuator	thermal	Three	Requires a	IJ23, IJ24,
	expansion	methods of	PTFE	IJ27, IJ28,
	(CTE) such as	PTFE	deposition	IJ29, IJ30,
	polytetra-	deposition	process, which	IJ31, IJ42,
	fluoroethylene	are under	is not yet	IJ43, IJ44
	(PTFE) is used.	develop-	standard in
	As high CTE	ment:	ULSI fabs
	materials are	chemical	PTFE
	usually non-	vapor	deposition
	conductive, a	deposition	cannot be
	heater	(CVD),	followed with
	fabricated from	spin coating,	high
	a conductive	and	temperature
	material is	evaporation	(above
	incorporated. A	PTFE is a	350° C.)
	50 μm long	candidate	processing
	PTFE bend	for low	Pigmented inks
	actuator with	dielectric	may be
	polysilicon	constant	infeasible, as
	heater and 15	insulation	pigment
	mW power in-	in ULSI	particles may
	put can provide	Very low	jam the bend
	180 μN force	power	actuator
	and 10 μm	consumption
	deflection.	Many ink
	Actuator	types can be
	motions	used
	include:	Simple
	Bend	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
Con-	A polymer	High force	Requires	IJ24
ductive	with a high	can be	special
polymer	coefficient of	generated	materials
thermo-	thermal	Very low	development
elastic	expansion	power	(High CTE
actuator	(such as PTFE)	consumption	conductive
	is doped with	Many ink	polymer)
	conducting	types can	Requires a
	substances to	be used	PTFE
	increase its	Simple	deposition
	conductivity to	planar	process, which
	about 3 orders	fabrication	is not yet
	of magnitude	Small chip	standard in
	below that of	area	ULSI fabs
	copper. The	required for	PTFE
	conducting	each actuator	deposition
	polymer	Fast	cannot be
	expands when	operation	followed
	resistively	High	with high
	heated.	efficiency	temperature
	Examples of	CMOS	(above
	conducting	compatible	350° C.)
	dopants	voltages and	processing
	include:	currents	Evaporation
	Carbon	Easy	and CVD
	nanotubes	extension	deposition
	Metal fibers	from single	techniques
	Conductive	nozzles to	cannot
	polymers such	pagewidth	be used
	as doped	print heads	Pigmented
	polythiophene		inks may be
	Carbon		infeasible, as
	granules		pigment
			particles may
			jam the bend
			actuator
Shape	A shape	High force is	Fatigue limits	IJ26
memory	memory alloy	available	maximum
alloy	such as TiNi	(stresses	number of
	(also known as	of hundreds	cycles
	Nitinol -	of MPa)	Low strain
	Nickel	Large strain	(1%) is
	Titanium alloy	is available	required to
	developed at	(more than	extend fatigue
	the Naval	3%)	resistance
	Ordnance	High	Cycle rate
	Laboratory) is	corrosion	limited by
	thermally	resistance	heat removal
	switched	Simple	Requires
	between its	construction	unusual
	weak	Easy	materials
	martensitic	extension	(TiNi)
	state and its	from single	The latent
	high stiffness	nozzles to	heat of
	austenitic state.	pagewidth	transformation
	The shape of	print heads	must be
	the actuator in	Low voltage	provided
	its martensitic	operation	High current
	state is		operation
	deformed		Requires pre-
	relative to		stressing to
	the austenitic		distort the
	shape.		martensitic
	The shape		state
	change causes
	ejection of a
	drop.
Linear	Linear	Linear	Requires	IJ12
Magnetic	magnetic	Magnetic	unusual semi-
Actuator	actuators	actuators	conductor
	include the	can be	materials such
	Linear	constructed	as soft
	Induction	with high	magnetic alloys
	Actuator (LIA),	thrust, long	(e.g. CoNiFe)
	Linear	travel, and	Some varieties
	Permanent	high	also require
	Magnet	efficiency	permanent
	Synchronous	using planar	magnetic
	Actuator	semi-	materials
	(LPMSA),	conductor	such as
	Linear	fabrication	Neodymium
	Reluctance	techniques	iron boron
	Synchronous	Long	(NdFeB)
	Actuator	actuator	Requires
	(LRSA),	travel is	complex
	Linear	available	multi-phase
	Switched	Medium	drive circuitry
	Reluctance	force is	High current
	Actuator	available	operation
	(LSRA), and	Low voltage
	the Linear	operation
	Stepper
	Actuator
	(LSA).

BASIC OPERATION MODE

Actuator	This is the	Simple	Drop repetition	Thermal
directly	simplest mode	operation	rate is usually	ink jet
pushes	of operation:	No external	limited to	Piezoelectric
	the ink actuator	fields	around 10 kHz.	ink jet
	directly	required	However, this	IJ01, IJ02,
	supplies	Satellite	is not	IJ03, IJ04,
	sufficient	drops can be	fundamental to	IJ05, IJ06,
	kinetic energy	avoided if	the method, but	IJ07, IJ09,
	to expel the	drop velocity	is related to the	IJ11, IJ12,
	drop. The drop	is less than	refill method	IJ14, IJ16,
	must have a	4 m/s	normally used	IJ20, IJ22,
	sufficient	Can be	All of the drop	IJ23, IJ24,
	velocity to	efficient,	kinetic energy	IJ25, IJ26,
	overcome the	depending	must be	IJ27, IJ28,
	surface tension.	upon the	provided by the	IJ29, IJ30,
		actuator used	actuator	IJ31, IJ32,
			Satellite drops	IJ33, IJ34,
			usually form if	IJ35, IJ36,
			drop velocity is	IJ37, IJ38,
			greater than	IJ39, IJ40,
			4.5 m/s	IJ41, IJ42,
				IJ43, IJ44
Proximity	The drops to be	Very simple	Requires close	Silverbrook,
	printed are	print head	proximity	EP 0771 658
	selected by	fabrication	between the	A2 and
	some manner	can be used	print head and	related
	(e.g. thermally	The drop	the print media	patent
	induced surface	selection	or transfer	applications
	tension	means does	roller
	reduction of	not need to	May require
	pressurized	provide the	two print heads
	ink). Selected	energy	printing
	drops are	required to	alternate rows
	separated from	separate the	of the image
	the ink in the	drop from	Monolithic
	nozzle by	the nozzle	color print
	contact with		heads are
	the print		difficult
	medium or a
	transfer roller.
Electro-	The drops to be	Very simple	Requires very	Silverbrook,
static	printed are	print head	high electro-	EP 0771 658
pull on	selected by	fabrication	static field	A2 and
ink	some manner	can be used	Electrostatic	related
	(e.g. thermally	The drop	field for small	patent
	induced surface	selection	nozzle sizes is	applications
	tension	means does	above air	Tone-Jet
	reduction of	not need to	breakdown
	pressurized	provide the	Electrostatic
	ink). Selected	energy	field may
	drops are	required to	attract dust
	separated from	separate the
	the ink in the	drop from
	nozzle by a	the nozzle
	strong electric
	field.
Magnetic	The drops to be	Very simple	Requires	Silverbrook,
pull on	printed are	print head	magnetic ink	EP 0771 658
ink	selected by	fabrication	Ink colors other	A2 and
	some manner	can be used	than black are	related
	(e.g. thermally	The drop	difficult	patent
	induced surface	selection	Requires very	applications
	tension	means does	high magnetic
	reduction of	not need	fields
	pressurized	to provide
	ink). Selected	the energy
	drops are	required to
	separated from	separate the
	the ink in	drop from
	the nozzle by	the nozzle
	a strong
	magnetic field
	acting on the
	magnetic ink.
Shutter	The actuator	High speed	Moving parts	IJ13, IJ17,
	moves a shutter	(>50 kHz)	are required	IJ21
	to block ink	operation	Requires ink
	flow to the	can be	pressure
	nozzle. The ink	achieved due	modulator
	pressure is	to reduced	Friction and
	pulsed at a	refill time	wear must be
	multiple of the	Drop timing	considered
	drop ejection	can be very	Stiction is
	frequency.	accurate	possible
		The actuator
		energy can
		be very low
Shuttered	The actuator	Actuators	Moving parts	IJ08, IJ15,
grill	moves a shutter	with small	are required	IJ18, IJ19
	to block ink	travel can	Requires ink
	flow through a	be used	pressure
	grill to the	Actuators	modulator
	nozzle. The	with small	Friction and
	shutter	force can be	wear must be
	movement need	used	considered
	only be equal	High speed	Stiction is
	to the width of	(>50 kHz)	possible
	the grill holes.	operation
		can be
		achieved
Pulsed	A pulsed	Extremely	Requires an	IJ10
magnetic	magnetic field	low energy	external pulsed
pull on	attracts an ‘ink	operation is	magnetic field
ink	pusher’ at the	possible	Requires
pusher	drop ejection	No heat	special
	frequency. An	dissipation	materials for
	actuator	problems	both the
	controls a		actuator and
	catch, which		the ink pusher
	prevents the		Complex
	ink pusher		construction
	from moving
	when a drop is
	not to be
	ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)

None	The actuator	Simplicity of	Drop ejection	Most ink
	directly fires	construction	energy must be	jets,
	the ink drop,	Simplicity of	supplied by	including
	and there is no	operation	individual	piezoelectric
	external field	Small	nozzle actuator	and thermal
	or other	physical size		bubble.
	mechanism			IJ01, IJ02,
	required.			IJ03, IJ04,
				IJ05, IJ07,
				IJ09, IJ11,
				IJ12, IJ14,
				IJ20, IJ22,
				IJ23, IJ24,
				IJ25, IJ26,
				IJ27, IJ28,
				IJ29, IJ30,
				IJ31, IJ32,
				IJ33, IJ34,
				IJ35, IJ36,
				IJ37, IJ38,
				IJ39, IJ40,
				IJ41, IJ42,
				IJ43, IJ44
Oscillating	The ink	Oscillating	Requires	Silverbrook,
ink	pressure	ink pressure	external ink	EP 0771 658
pressure	oscillates,	can provide	pressure	A2 and
(including	providing much	a refill pulse,	oscillator	related
acoustic	of the drop	allowing	Ink pressure	patent
stim-	ejection	higher	phase and	applications
ulation)	energy. The	operating	amplitude	IJ08, IJ13,
	actuator selects	speed	must be	IJ15, IJ17,
	which drops	The	carefully	IJ18, IJ19,
	are to be fired	actuators	controlled	IJ21
	by selectively	may operate	Acoustic
	blocking or	with much	reflections
	enabling	lower energy	in the ink
	nozzles. The	Acoustic	chamber
	ink pressure	lenses can	must be
	oscillation may	be used to	designed
	be achieved by	focus the	for
	vibrating the	sound on the
	print head, or	nozzles
	preferably by
	an actuator in
	the ink supply.
Media	The print head	Low power	Precision	Silverbrook,
proximity	is placed in	High	assembly	EP 0771 658
	close proximity	accuracy	required	A2 and
	to the print	Simple	Paper fibers	related
	medium.	print head	may cause	patent
	Selected drops	construction	problems	applications
	protrude from		Cannot print
	the print head		on rough
	further than		substrates
	unselected
	drops, and
	contact the
	print medium.
	The drop soaks
	into the
	medium fast
	enough to
	cause drop
	separation.
Transfer	Drops are	High	Bulky	Silverbrook,
roller	printed to a	accuracy	Expensive	EP 0771 658
	transfer roller	Wide range	Complex	A2 and
	instead of	of print	construction	related
	straight to the	substrates		patent
	print medium.	can be used		applications
	A transfer	Ink can be		Tektronix
	roller can also	dried on		hot melt
	be used for	the transfer		piezoelectric
	proximity drop	roller		ink jet
	separation.			Any of the
				IJ series
Electro-	An electric	Low power	Field strength	Silverbrook,
static	field is used to	Simple	required for	EP 0771 658
	accelerate	print head	separation of	A2 and
	selected drops	construction	small drops is	related
	towards the		near or above	patent
	print medium.		air breakdown	applications
				Tone-Jet
Direct	A magnetic	Low power	Requires	Silverbrook,
magnetic	field is used to	Simple	magnetic ink	EP 0771 658
field	accelerate	print head	Requires strong	A2 and
	selected drops	construction	magnetic field	related
	of magnetic ink			patent
	towards the			applications
	print medium.
Cross	The print head	Does not	Requires	IJ06, IJ16
magnetic	is placed in a	require	external
field	constant	magnetic	magnet
	magnetic field.	materials	Current
	The Lorenz	to be	densities may
	force in a	integrated	be high,
	current	in the	resulting in
	carrying wire	print head	electro-
	is used to move	manu-	migration
	the actuator.	facturing	problems
		process
Pulsed	A pulsed	Very low	Complex	IJ10
magnetic	magnetic field	power	print head
field	is used to	operation is	construction
	cyclically	possible	Magnetic
	attract a	Small print	materials
	paddle, which	head size	required in
	pushes on the		print head
	ink. A small
	actuator moves
	a catch, which
	selectively
	prevents
	the paddle from
	moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD

None	No actuator	Operational	Many actuator	Thermal
	mechanical	simplicity	mechanisms	Bubble
	amplification		have	Ink jet
	is used. The		insufficient	IJ01, IJ02,
	actuator		travel, or	IJ06, IJ07,
	directly drives		insufficient	IJ16, IJ25,
	the drop		force, to	IJ26
	ejection		efficiently
	process.		drive the drop
			ejection
			process
Differ-	An actuator	Provides	High stresses	Piezoelectric
ential	material	greater	are involved	IJ03, IJ09,
expansion	expands more	travel in	Care must be	IJ17, IJ18,
bend	on one side	a reduced	taken that the	IJ19, IJ20,
actuator	than on the	print head	materials do	IJ21, IJ22,
	other. The	area	not delaminate	IJ23, IJ24,
	expansion may		Residual bend	IJ27, IJ29,
	be thermal,		resulting from	IJ30, IJ31,
	piezoelectric,		high	IJ32, IJ33,
	magneto-		temperature or	IJ34, IJ35,
	strictive, or		high stress	IJ36, IJ37,
	other		during	IJ38, IJ39,
	mechanism.		formation	IJ42, IJ43,
	The bend			IJ44
	actuator
	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	temperature	are involved
actuator	the two outside	stability	Care must be
	layers are	High speed,	taken that the
	identical. This	as a new	materials do
	cancels bend	drop can be	not delaminate
	due to ambient	fired before
	temperature	heat
	and residual	dissipates
	stress. The	Cancels
	actuator only	residual
	responds to	stress of
	transient	formation
	heating of one
	side or the
	other.
Reverse	The actuator	Better	Fabrication	IJ05, IJ11
spring	loads a spring.	coupling to	complexity
	When the	the ink	High stress in
	actuator is		the spring
	turned off, 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
	stacked. This	Reduced	complexity	ink jets
	can be	drive	Increased	IJ04
	appropriate	voltage	possibility of
	where actuators		short circuits
	require high		due to pinholes
	electric field
	strength, such
	as electrostatic
	and piezo-
	electric
	actuators.
Multiple	Multiple	Increases	Actuator forces	IJ12, IJ13,
actuators	smaller	the force	may not add	IJ18, IJ20,
	actuators	available	linearly,	IJ22, IJ28,
	are used	from an	reducing	IJ42, IJ43
	simultaneously	actuator	efficiency
	to move the	Multiple
	ink. Each	actuators
	actuator need	can be
	provide only a	positioned
	portion of the	to control
	force required.	ink flow
		accurately
Linear	A linear spring	Matches low	Requires print	IJ15
Spring	is used to	travel	head area for
	transform a	actuator with	the spring
	motion with	higher travel
	small travel	requirements
	and high force	Non-contact
	into a longer	method of
	travel, lower	motion
	force motion.	trans-
		formation
Coiled	A bend	Increases	Generally	IJ17, IJ21,
actuator	actuator is	travel	restricted to	IJ34, IJ35
	coiled to	Reduces chip	planar imple-
	provide greater	area	mentations due
	travel in a	Planar	to extreme
	reduced chip	implemen-	fabrication
	area.	tations are	difficulty
		relatively	in other
		easy to	orientations.
		fabricate.
Flexure	A bend	Simple	Care must be	IJ10, IJ19,
bend	actuator has a	means of	taken not to	IJ33
actuator	small region	increasing	exceed the
	near the fixture	travel of	elastic limit in
	point, which	a bend	the flexure area
	flexes much	actuator	Stress
	more readily		distribution is
	than the		very uneven
	remainder of		Difficult to
	the actuator.		accurately
	The actuator		model with
	flexing is		finite element
	effectively		analysis
	converted from
	an even coiling
	to an angular
	bend, resulting
	in greater travel
	of the actuator
	tip.
Catch	The actuator	Very low	Complex	IJ10
	controls a small	actuator	construction
	catch. The	energy	Requires
	catch either	Very small	external force
	enables or	actuator	Unsuitable for
	disables	size	pigmented inks
	movement of
	an ink pusher
	that is
	controlled in a
	bulk manner.
Gears	Gears can be	Low force,	Moving parts	IJ13
	used to	low travel	are required
	increase travel	actuators can	Several
	at the expense	be used	actuator cycles
	of duration.	Can be	are required
	Circular gears,	fabricated	More complex
	rack and	using	drive
	pinion,	standard	electronics
	ratchets, and	surface	Complex
	other gearing	MEMS	construction
	methods can be	processes	Friction,
	used.		friction, and
			wear are
			possible
Buckle	A buckle plate	Very fast	Must stay	S. Hirata
plate	can be used to	movement	within elastic	et al, “An
	change a slow	achievable	limits of the	Ink-jet Head
	actuator into a		materials for	Using
	fast motion. It		long device life	Diaphragm
	can also		High stresses	Micro-
	convert a high		involved	actuator”,
	force, low		Generally high	Proc. IEEE
	travel actuator		power	MEMS,
	into a high		requirement	Feb. 1996,
	travel, medium			pp 418-423.
	force motion.			IJ18, IJ27
Tapered	A tapered	Linearizes	Complex	IJ14
magnetic	magnetic pole	the magnetic	construction
pole	can increase	force/
	travel at the	distance
	expense of	curve
	force.
Lever	A lever and	Matches low	High stress	IJ32, IJ36,
	fulcrum is used	travel	around the	IJ37
	to transform a	actuator with	fulcrum
	motion with	higher travel
	small travel	requirements
	and high force	Fulcrum area
	into a motion	has no
	with longer	linear
	travel and	movement,
	lower force.	and can be
	The lever can	used for
	also reverse the	a fluid seal
	direction of
	travel.
Rotary	The actuator is	High	Complex	IJ28
impeller	connected to a	mechanical	construction
	rotary impeller.	advantage	Unsuitable for
	A small	The ratio of	pigmented inks
	angular	force to
	deflection of	travel of the
	the actuator	actuator can
	results in a	be matched
	rotation of the	to the nozzle
	impeller vanes,	requirements
	which push the	by varying
	ink against	the number
	stationary	of impeller
	vanes and out	vanes
	of the nozzle.
Acoustic	A refractive or	No moving	Large area	1993
lens	diffractive (e.g.	parts	required	Hadimioglu
	zone plate)		Only relevant	et al, EUP
	acoustic lens is		for acoustic ink	550,192
	used to		jets	1993 Elrod
	concentrate			et al, EUP
	sound waves.			572,220
Sharp	A sharp point	Simple	Difficult to	Tone-jet
conductive	is used to	construction	fabricate using
point	concentrate an		standard VLSI
	electrostatic		processes for a
	field.		surface ejecting
			inkjet
			Only relevant
			for electrostatic
			ink jets

ACTUATOR MOTION

Volume	The volume of	Simple	High energy is	Hewlett-
expansion	the actuator	construction	typically	Packard
	changes,	in the case	required to	Thermal
	pushing the	of thermal	achieve volume	Ink jet
	ink in all	ink jet	expansion. This	Canon
	directions.		leads to	Bubblejet
			thermal stress,
			cavitation, and
			kogation in
			thermal ink jet
			implemen-
			tations
Linear,	The actuator	Efficient	High	IJ01, IJ02,
normal	moves in a	coupling to	fabrication	IJ04, IJ07,
to chip	direction	ink drops	complexity	IJ11, IJ14
surface	normal to the	ejected	may be
	print head	normal to	required to
	surface. The	the surface	achieve
	nozzle is		perpendicular
	typically in		motion
	the line of
	movement.
Parallel	The actuator	Suitable for	Fabrication	IJ12, IJ13,
to chip	moves parallel	planar	complexity	IJ15, IJ33,
surface	to the print	fabrication	Friction	IJ34, IJ35,
	head surface.		Stiction	IJ36
	Drop ejection
	may still be
	normal to the
	surface.
Membrane	An actuator	The effective	Fabrication	1982
push	with a high	area of the	complexity	Howkins
	force but small	actuator	Actuator size	U.S. Pat No.
	area is used to	becomes the	Difficulty of	4,459,601
	push a stiff	membrane	integration in a
	membrane that	area	VLSI process
	is in contact
	with the ink.
Rotary	The actuator	Rotary levers	Device	IJ05, IJ08,
	causes the	may be used	complexity	IJ13, IJ28
	rotation of	to increase	May have
	some element,	travel	friction at a
	such a grill	Small chip	pivot point
	or impeller	area
		requirements
Bend	The actuator	A very small	Requires the	1970 Kyser
	bends when	change in	actuator to be	et al
	energized. This	dimensions	made from at	U.S. Pat No.
	may be due to	can be	least two	3,946,398
	differential	converted to	distinct layers,	1973
	thermal	a large	or to have a	Stemme
	expansion,	motion.	thermal	U.S. Pat No.
	piezoelectric		difference	3,747,120
	expansion,		across the	IJ03, IJ09,
	magneto-		actuator	IJ10, IJ19,
	striction, or			IJ23, IJ24,
	other form of			IJ25, IJ29,
	relative			IJ30, IJ31,
	dimensional			IJ33, IJ34,
	change.			IJ35
Swivel	The actuator	Allows	Inefficient	IJ06
	swivels around	operation	coupling to the
	a central pivot,	where the	ink motion
	This motion is	net linear
	suitable where	force on
	there are	the paddle
	opposite forces	is zero
	applied to	Small chip
	opposite sides	area
	of the paddle,	requirements
	e.g. Lorenz
	force.
Straighten	The actuator is	Can be used	Requires	IJ26, IJ32
	normally bent,	with shape	careful balance
	and straightens	memory	of stresses to
	when	alloys	ensure that the
	energized.	where the	quiescent bend
		austenitic	is accurate
		phase is
		planar
Double	The actuator	One actuator	Difficult to	IJ36, IJ37,
bend	bends in one	can be used	make the drops	IJ38
	direction when	to power two	ejected by both
	one element is	nozzles.	bend directions
	energized, and	Reduced	identical.
	bends the other	chip size.	A small
	way when	Not sensitive	efficiency loss
	another	to ambient	compared to
	element is	temperature	equivalent
	energized.		single bend
			actuators.
Shear	Energizing the	Can increase	Not readily	1985
	actuator causes	the effective	applicable to	Fishbeck
	a shear motion	travel of	other actuator	U.S. Pat No.
	in the actuator	piezoelectric	mechanisms	4,584,590
	material.	actuators
Radial	The actuator	Relatively	High force	1970 Zoltan
con-	squeezes an	easy to	required	U.S. Pat No.
striction	ink reservoir,	fabricate	Inefficient	3,683,212
	forcing ink	single	Difficult to
	from a	nozzles	integrate with
	constricted	from glass	VLSI
	nozzle.	tubing as	processes
		macroscopic
		structures
Coil/	A coiled	Easy to	Difficult to	IJ17, IJ21,
uncoil	actuator uncoils	fabricate	fabricate for	IJ34, IJ35
	or coils more	as a planar	non-planar
	tightly. The	VLSI	devices
	motion of the	process	Poor out-of-
	free end of the	Small area	plane stiffness
	actuator ejects	required,
	the ink.	therefore
		low cost
Bow	The actuator	Can increase	Maximum	IJ16, IJ18,
	bows (or	the speed	travel is	IJ27
	buckles) in the	of travel	constrained
	middle when	Mechan-	High force
	energized.	ically	required
		rigid
Push-Pull	Two actuators	The structure	Not readily	IJ18
	control a	is pinned at	suitable for ink
	shutter. One	both ends,	jets which
	actuator pulls	so has a high	directly push
	the shutter,	out-of-plane	the ink
	and the other	rigidity
	pushes it.
Curl	A set of	Good fluid	Design	IJ20, IJ42
inwards	actuators curl	flow to the	complexity
	inwards to	region
	reduce the	behind the
	volume of ink	actuator
	that they	increases
	enclose.	efficiency
Curl	A set of	Relatively	Relatively large	IJ43
outwards	actuators curl	simple	chip area
	outwards,	construction
	pressurizing
	ink in a
	chamber
	surrounding the
	actuators, and
	expelling ink
	from a nozzle
	in the chamber.
Iris	Multiple vanes	High	High	IJ22
	enclose a	efficiency	fabrication
	volume of ink.	Small chip	complexity
	These	area	Not suitable for
	simultaneously		pigmented inks
	rotate, reducing
	the volume
	between the
	vanes.
Acoustic	The actuator	The actuator	Large area	1993
vibration	vibrates at a	can be	required for	Hadimioglu
	high frequency.	physically	efficient	et al, EUP
		distant	operation at	550,192
		from the ink	useful	1993 Elrod
			frequencies	et al, EUP
			Acoustic	572,220
			coupling and
			crosstalk
			Complex drive
			circuitry
			Poor control of
			drop volume
			and position
None	In various ink	No moving	Various other	Silverbrook,
	jet designs the	parts	tradeoffs are	EP 0771 658
	actuator does		required to	A2 and
	not move.		eliminate	related
			moving parts	patent
				applications
				Tone-jet

NOZZLE REFILL METHOD

Surface	This is the	Fabrication	Low speed	Thermal
tension	normal way	simplicity	Surface tension	ink jet
	that ink jets are	Operational	force relatively	Piezoelectric
	refilled. After	simplicity	small compared	inkjet
	the actuator is		to actuator	IJ01-IJ07,
	energized, it		force	IJ10-IJ14,
	typically		Long refill	IJ16, IJ20,
	returns rapidly		time usually	IJ22-IJ45
	to its normal		dominates the
	position. This		total repetition
	rapid return		rate
	sucks in air
	through the
	nozzle 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	High speed	Requires	IJ08, IJ13,
oscillating	nozzle chamber	Low actuator	common ink	IJ15, IJ17,
ink	is provided at	energy, as	pressure	IJ18, IJ19,
pressure	a pressure that	the actuator	oscillator	IJ21
	oscillates at	need only	May not be
	twice the drop	open or close	suitable for
	ejection	the shutter,	pigmented inks
	frequency.	instead of
	When a drop is	ejecting the
	to be ejected,	ink drop
	the shutter 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,	Requires two	IJ09
actuator	actuator has	as the	independent
	ejected a drop a	nozzle is	actuators per
	second (refill)	actively	nozzle
	actuator is	refilled
	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	High refill	Surface spill	Silverbrook,
ink	a slight positive	rate,	must be	EP 0771 658
pressure	pressure. After	therefore a	prevented	A2 and
	the ink drop is	high drop	Highly hydro-	related
	ejected, the	repetition	phobic print	patent
	nozzle chamber	rate is	head surfaces	applications
	fills quickly as	possible	are required	Alternative
	surface tension			for:,
	and ink			IJ01-IJ07,
	pressure both			IJ10-IJ14,
	operate to refill			IJ16, IJ20,
	the nozzle.			IJ22-IJ45

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET

Long inlet	The ink inlet	Design	Restricts refill	Thermal
channel	channel to the	simplicity	rate	ink jet
	nozzle chamber	Operational	May result in a	Piezoelectric
	is made long	simplicity	relatively large	ink jet
	and relatively	Reduces	chip area	IJ42, IJ43
	narrow, relying	crosstalk	Only partially
	on viscous drag		effective
	to reduce inlet
	back-flow.
Positive	The ink is	Drop	Requires a	Silverbrook,
ink	under a	selection and	method (such	EP 0771 658
pressure	positive	separation	as a nozzle rim	A2 and
	pressure, so	forces	or effective	related
	that in the	can be	hydro-	patent
	quiescent state	reduced	phobizing, or	applications
	some of the ink	Fast refill	both) to	Possible
	drop already	time	prevent	operation
	protrudes from		flooding of the	of the
	the nozzle.		ejection surface	following:
	This reduces		of the print	IJ01-IJ07,
	the pressure in		head.	IJ09-IJ12,
	the nozzle			IJ14, IJ16,
	chamber which			IJ20, IJ22,
	is required to			IJ23-IJ34,
	eject a certain			IJ36-IJ41,
	volume of ink.			IJ44
	The reduction
	in chamber
	pressure results
	in a reduction
	in ink pushed
	out through the
	inlet.
Baffle	One or more	The refill	Design	TIP Thermal
	baffles are	rate is not	complexity	Ink Jet
	placed in the	as restricted	May increase	Tektronix
	inlet ink flow.	as the long	fabrication	piezoelectric
	When the	inlet method.	complexity	ink jet
	actuator is	Reduces	(e.g. Tektronix
	energized, the	crosstalk	hot melt
	rapid ink		Piezoelectric
	movement		print heads).
	creates eddies
	which 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	reduces	to most ink jet
restricts	disclosed by	back-flow	configurations
inlet	Canon, the	for edge-	Increased
	expanding	shooter	fabrication
	actuator	thermal	complexity
	(bubble) pushes	ink jet	Inelastic
	on a flexible	devices	deformation of
	flap that		polymer flap
	restricts the		results in creep
	inlet.		over extended
			use
Inlet	A filter is	Additional	Restricts refill	IJ04, IJ12,
filter	located	advantage	rate	IJ24, IJ27,
	between the ink	of ink	May result	IJ29, IJ30
	inlet and the	filtration	in complex
	nozzle	Ink filter	construction
	chamber. The	may be
	filter has a	fabricated
	multitude of	with no
	small holes or	additional
	slots,	process
	restricting ink	steps
	flow. The filter
	also removes
	particles which
	may block the
	nozzle.
Small inlet	The ink inlet	Design	Restricts refill	IJ02, IJ37,
compared	channel to the	simplicity	rate	IJ44
to nozzle	nozzle chamber		May result in a
	has a		relatively large
	substantially		chip area
	smaller cross		Only partially
	section than		effective
	that of the
	nozzle,
	resulting in
	easier ink
	egress out of
	the nozzle than
	out of the inlet.
Inlet	A secondary	Increases	Requires	IJ09
shutter	actuator	speed of	separate refill
	controls the	the ink-jet	actuator and
	position of a	print head	drive circuit
	shutter, closing	operation
	off the ink
	inlet when the
	main actuator
	is energized.
The inlet	The method	Back-flow	Requires	IJ01, IJ03,
is located	avoids the	problem is	careful design	IJ05, IJ06,
behind	problem of	eliminated	to minimize the	IJ07, IJ10,
the ink-	inlet back-flow		negative	IJ11, IJ14,
pushing	by arranging		pressure behind	IJ16, IJ22,
surface	the ink-pushing		the paddle	IJ23, IJ25,
	surface of the			IJ28, IJ31,
	actuator			IJ32, IJ33,
	between the			IJ34, IJ35,
	inlet and the			IJ36, IJ39,
	nozzle.			IJ40, IJ41
Part of the	The actuator	Significant	Small increase	IJ07, IJ20,
actuator	and a wall of	reductions	in fabrication	IJ26, IJ38
moves to	the ink	in back-	complexity
shut off	chamber are	flow can be
the inlet	arranged so	achieved
	that the motion	Compact
	of the actuator	designs
	closes off the	possible
	inlet.
Nozzle	In some	Ink	None related to	Silverbrook,
actuator	configurations	back-flow	ink back-flow	EP 0771 658
does not	of ink jet, there	problem is	on actuation	A2 and
result	is no expansion	eliminated		related
in ink	or movement			patent
back-flow	of an actuator			applications
	which may			Valve-jet
	cause ink			Tone-jet
	back-flow
	through the
	inlet.

NOZZLE CLEARING METHOD

Normal	All of the	No added	May not be	Most ink
nozzle	nozzles are	complexity	sufficient to	jet systems
firing	fired	on the	displace dried	IJ01, IJ02,
	periodically,	print head	ink	IJ03, IJ04,
	before the ink			IJ05, IJ06,
	has a chance to			IJ07, IJ09,
	dry. When not			IJ10, IJ11,
	in use the			IJ12, IJ14,
	nozzles are			IJ16, IJ20,
	sealed (capped)			IJ22, IJ23,
	against air.			IJ24, IJ25,
	The nozzle			IJ26, IJ27,
	firing is			IJ28, IJ29,
	usually			IJ30, IJ31,
	performed			IJ32, IJ33,
	during a special			IJ34, IJ36,
	clearing cycle,			IJ37, IJ38,
	after first			IJ39, IJ40,
	moving the			IJ41, IJ42,
	print head to			IJ43, IJ44,
	a cleaning			IJ45
	station.
Extra	In systems	Can be	Requires higher	Silverbrook,
power	which heat the	highly	drive voltage	EP 0771 658
to ink	ink, but do not	effective	for clearing	A2 and
heater	boil it under	if the	May require	related
	normal	heater is	larger drive	patent
	situations,	adjacent to	transistors	applications
	nozzle clearing	the nozzle
	can be
	achieved by
	overpowering
	the heater
	and boiling ink
	at the nozzle.
Rapid	The actuator is	Does not	Effectiveness	May be
succession	fired in rapid	require	depends	used with:
of actuator	succession.	extra drive	substantially	IJ01, IJ02,
pulses	In some	circuits	upon the	IJ03, IJ04,
	configurations,	on the	configuration	IJ05, IJ06,
	this may cause	print head	of the ink jet	IJ07, IJ09,
	heat build-up at	Can be	nozzle	IJ10, IJ11,
	the nozzle	readily		IJ14, IJ16,
	which boils the	controlled		IJ20, IJ22,
	ink, clearing	and		IJ23, IJ24,
	the nozzle.	initiated		IJ25, IJ27,
	In other	by digital		IJ28, IJ29,
	situations, it	logic		IJ30, IJ31,
	may cause			IJ32, IJ33,
	sufficient			IJ34, IJ36,
	vibrations to			IJ37, IJ38,
	dislodge			IJ39, IJ40,
	clogged			IJ41, IJ42,
	nozzles.			IJ43, IJ44,
				IJ45
Extra	Where an	A simple	Not suitable	May be
power to	actuator is	solution	where there is	used with:
ink	not normally	where	a hard limit to	IJ03, IJ09,
pushing	driven to the	applicable	actuator	IJ16, IJ20,
actuator	limit of its		movement	IJ23, IJ24,
	motion, nozzle			IJ25, IJ27,
	clearing may			IJ29, IJ30,
	be assisted by			IJ31, IJ32,
	providing an			IJ39, IJ40,
	enhanced drive			IJ41, IJ42,
	signal to the			IJ43, IJ44,
	actuator.			IJ45
Acoustic	An ultrasonic	A high	High	IJ08, IJ13,
resonance	wave is applied	nozzle	implementation	IJ15, IJ17,
	to the ink	clearing	cost if system	IJ18, IJ19,
	chamber. This	capability	does not	IJ21
	wave is of an	can be	already include
	appropriate	achieved	an acoustic
	amplitude and	May be	actuator
	frequency to	implemented
	cause sufficient	at very
	force at the	low cost
	nozzle to clear	in systems
	blockages. This	which
	is easiest to	already
	achieve if the	include
	ultrasonic wave	acoustic
	is at a resonant	actuators
	frequency of
	the ink cavity.
Nozzle	A micro-	Can clear	Accurate	Silverbrook,
clearing	fabricated plate	severely	mechanical	EP 0771 658
plate	is pushed	clogged	alignment is	A2 and
	against the	nozzles	required	related
	nozzles. The		Moving parts	patent
	plate has a post		are required	applications
	for every		There is risk of
	nozzle. A post		damage to the
	moves through		nozzles
	each nozzle,		Accurate
	displacing		fabrication
	dried ink.		is required
Ink	The pressure of	May be	Requires	May be
pressure	the ink is	effective	pressure pump	used with
pulse	temporarily	where	or other	all IJ
	increased so	other	pressure	series
	that ink streams	methods	actuator	ink jets
	from all of the	cannot	Expensive
	nozzles. This	be used	Wasteful of ink
	may be used in
	conjunction
	with actuator
	energizing.
Print	A flexible	Effective	Difficult to use	Many
head	‘blade’ is	for planar	if print head	ink jet
wiper	wiped across	print head	surface is non-	systems
	the print head	surfaces	planar or very
	surface. The	Low cost	fragile
	blade is usually		Requires
	fabricated from		mechanical
	a flexible		parts
	polymer, e.g.		Blade can wear
	rubber or		out in high
	synthetic		volume print
	elastomer.		systems
Separate	A separate	Can be	Fabrication	Can be used
ink	heater is	effective	complexity	with many IJ
boiling	provided at the	where other		series ink
heater	nozzle although	nozzle		jets
	the normal	clearing
	drop ejection	methods
	mechanism	cannot
	does not	be used
	require it. The	Can be
	heaters do not	implemented
	require	at no
	individual drive	additional
	circuits, as	cost in
	many nozzles	some ink
	can be cleared	jet con-
	simultaneously,	figurations
	and no imaging
	is required.

NOZZLE PLATE CONSTRUCTION

Electro-	A nozzle plate	Fabrication	High	Hewlett
formed	is separately	simplicity	temperatures	Packard
nickel	fabricated from		and pressures	Thermal
	electroformed		are required to	Ink jet
	nickel, and		bond nozzle
	bonded to the		plate
	print head chip.		Minimum
			thickness
			constraints
			Differential
			thermal
			expansion
Laser	Individual	No masks	Each hole must	Canon
ablated or	nozzle holes	required	be individually	Bubblejet
drilled	are ablated by	Can be	formed	1988 Sercel
polymer	an intense UV	quite fast	Special	et al., SPIE,
	laser in a	Some	equipment	Vol. 998
	nozzle plate,	control	required	Excimer
	which is	over	Slow where	Beam
	typically a	nozzle	there are many	Applications,
	polymer such	profile is	thousands of	pp. 76-83
	as polyimide or	possible	nozzles per	1993
	polysulphone	Equipment	print head	Watanabe
		required is	May produce	et al.,
		relatively	thin burrs at	U.S. Pat No.
		low cost	exit holes	5,208,604
Silicon	A separate	High	Two part	K. Bean,
micro-	nozzle plate is	accuracy is	construction	IEEE Trans-
machined	micromachined	attainable	High cost	actions on
	from single		Requires	Electron
	crystal silicon,		precision	Devices,
	and bonded to		alignment	Vol. ED-25,
	the print head		Nozzles may	No. 10,
	wafer.		be clogged by	1978, pp
			adhesive	1185-1195
				Xerox 1990
				Hawkins
				et al.,
				U.S. Pat No.
				4,899,181
Glass	Fine glass	No	Very small	1970 Zoltan
capillaries	capillaries are	expensive	nozzle sizes are	U.S. Pat No.
	drawn from	equipment	difficult to	3,683,212
	glass tubing.	required	form
	This method	Simple	Not suited
	has been used	to make	for mass
	for making	single	production
	individual	nozzles
	nozzles, but is
	difficult to use
	for bulk
	manufacturing
	of print heads
	with thousands
	of nozzles.
Mono-	The nozzle	High	Requires	Silverbrook,
lithic,	plate is	accuracy	sacrificial layer	EP 0771 658
surface	deposited as a	(<1 μm)	under the	A2 and
micro-	layer using	Monolithic	nozzle plate to	related
machined	standard VLSI	Low cost	form the nozzle	patent
using	deposition	Existing	chamber	applications
VLSI	techniques.	processes	Surface may be	IJ01, IJ02,
litho-	Nozzles are	can be	fragile to the	IJ04, IJ11,
graphic	etched in the	used	touch	IJ12, IJ17,
processes	nozzle plate			IJ18, IJ20,
	using VLSI			IJ22, IJ24,
	lithography and			IJ27, IJ28,
	etching.			IJ29, IJ30,
				IJ31, IJ32,
				IJ33, IJ34,
				IJ36, IJ37,
				IJ38, IJ39,
				IJ40, IJ41,
				IJ42, IJ43,
				IJ44
Mono-	The nozzle	High	Requires long	IJ03, IJ05,
lithic,	plate is a	accuracy	etch times	IJ06, IJ07,
etched	buried etch	(<1 μm)	Requires a	IJ08, IJ09,
through	stop in the	Monolithic	support wafer	IJ10, IJ13,
substrate	wafer. Nozzle	Low cost		IJ14, IJ15,
	chambers are	No		IJ16, IJ19,
	etched in the	differential		IJ21, IJ23,
	front of the	expansion		IJ25, IJ26
	wafer, and the
	wafer is
	thinned from
	the backside.
	Nozzles are
	then etched in
	the etch
	stop layer.
No nozzle	Various	No nozzles	Difficult to	Ricoh 1995
plate	methods have	to become	control drop	Sekiya
	been tried to	clogged	position	et al USP
	eliminate the		accurately	U.S. Pat No.
	nozzles		Crosstalk	5,412,413
	entirely, to		problems	1993
	prevent nozzle			Hadimioglu
	clogging.			et al EUP
	These include			550,192
	thermal bubble			1993 Elrod
	mechanisms			et al EUP
	and acoustic			572,220
	lens
	mechanisms
Trough	Each drop	Reduced	Drop firing	IJ35
	ejector has a	manu-	direction is
	trough through	facturing	sensitive to
	which a paddle	complexity	wicking.
	moves. There	Monolithic
	is no nozzle
	plate.
Nozzle slit	The elimination	No nozzles	Difficult to	1989 Saito
instead of	of nozzle holes	to become	control drop	et al
individual	and replace-	clogged	position	U.S. Pat No.
nozzles	ment by a slit		accurately	4,799,068
	encompassing		Crosstalk
	many actuator		problems
	positions
	reduces nozzle
	clogging, but
	increases
	crosstalk due to
	ink surface
	waves

DROP EJECTION DIRECTION

Edge	Ink flow is	Simple	Nozzles limited	Canon
(‘edge	along the	construction	to edge	Bubblejet
shooter’)	surface of the	No silicon	High resolution	1979 Endo
	chip, and ink	etching	is difficult	et al GB
	drops are	required	Fast color	patent
	ejected from	Good heat	printing	2,007,162
	the chip edge.	sinking	requires one	Xerox
		via substrate	print head per	heater-in-pit
		Mechanic-	color	1990
		ally strong		Hawkins
		Ease of		et al
		chip		U.S. Pat No.
		handing		4,899,181
				Tone-jet
Surface	Ink flow is	No bulk	Maximum ink	Hewlett-
(‘roof	along the	silicon	flow is severely	Packard TIJ
shooter’)	surface of the	etching	restricted	1982 Vaught
	chip, and ink	required		et al
	drops are	Silicon can		U.S. Pat No.
	ejected from	make an		4,490,728
	the chip	effective		IJ02, IJ11,
	surface, normal	heat sink		IJ12, IJ20,
	to the plane of	Mechanical		IJ22
	the chip.	strength
Through	Ink flow is	High ink	Requires bulk	Silverbrook,
chip,	through the	flow	silicon etching	EP 0771 658
forward	chip, and ink	Suitable for		A2 and
(‘up	drops are	pagewidth		related
shooter’)	ejected from	print heads		patent
	the front	High nozzle		applications
	surface of	packing		IJ04, IJ17,
	the chip.	density		IJ18, IJ24,
		therefore		IJ27-IJ45
		low manu-
		facturing
		cost
Through	Ink flow is	High ink	Requires wafer	IJ01, IJ03,
chip,	through the	flow	thinning	IJ05, IJ06,
reverse	chip, and ink	Suitable for	Requires	IJ07, IJ08,
(‘down	drops are	pagewidth	special	IJ09, IJ10,
shooter’)	ejected from	print heads	handling during	IJ13, IJ14,
	the rear	High nozzle	manufacture	IJ15, IJ16,
	surface of	packing		IJ19, IJ21,
	the chip.	density		IJ23, IJ25,
		therefore		IJ26
		low manu-
		facturing
		cost
Through	Ink flow is	Suitable for	Pagewidth print	Epson
actuator	through the	piezoelectric	heads require	Stylus
	actuator, which	print heads	several	Tektronix
	is not		thousand	hot melt
	fabricated as		connections to	piezoelectric
	part of the		drive circuits	ink jets
	same substrate		Cannot be
	as the drive		manufactured
	transistors.		in standard
			CMOS fabs
			Complex
			assembly
			required

INK TYPE

Aqueous,	Water based	Environ-	Slow drying	Most
dye	ink which	mentally	Corrosive	existing
	typically	friendly	Bleeds on	ink jets
	contains: water,	No odor	paper	All IJ series
	dye, surfactant,		May strike-	ink jets
	humectant, and		through	Silverbrook,
	biocide.		Cockles paper	EP 0771 658
	Modern ink			A2 and
	dyes have high			related
	water-fastness,			patent
	light fastness			applications
Aqueous,	Water based	Environ-	Slow drying	IJ02, IJ04,
pigment	ink which	mentally	Corrosive	IJ21, IJ26,
	typically	friendly	Pigment may	IJ27, IJ30
	contains: water,	No odor	clog nozzles	Silverbrook,
	pigment,	Reduced	Pigment may	EP 0771 658
	surfactant,	bleed	clog actuator	A2 and
	humectant, and	Reduced	mechanisms	related
	biocide.	wicking	Cockles paper	patent
	Pigments have	Reduced		applications
	an advantage in	strike-		Piezoelectric
	reduced bleed,	through		inkjets
	wicking and			Thermal
	strikethrough.			ink jets
				(with
				significant
				restrictions)
Methyl	MEK is a	Very fast	Odorous	All IJ series
Ethyl	highly volatile	drying	Flammable	ink jets
Ketone	solvent used	Prints on
(MEK)	for industrial	various
	printing on	substrates
	difficult	such as
	surfaces such	metals and
	as aluminum	plastics
	cans.
Alcohol	Alcohol based	Fast drying	Slight odor	All IJ series
(ethanol,	inks can be	Operates at	Flammable	ink jets
2-butanol,	used where the	subfreezing
and	printer must	temperatures
others)	operate at	Reduced
	temperatures	paper cockle
	below the	Low cost
	freezing point
	of water. An
	example of this
	is in-camera
	consumer
	photographic
	printing.
Phase	The ink is solid	No drying	High viscosity	Tektronix
change	at room	time - ink	Printed ink	hot melt
(hot melt)	temperature,	instantly	typically has a	piezoelectric
	and is melted	freezes on	‘waxy’ feel	ink jets
	in the print	the print	Printed pages	1989 Nowak
	head before	medium	may ‘block’	U.S. Pat No.
	jetting. Hot	Almost	Ink temperature	4,820,346
	melt inks are	any print	may be above	All IJ series
	usually wax	medium can	the curie point	ink jets
	based, with a	be used	of permanent
	melting point	No paper	magnets
	around 80° C.	cockle	Ink heaters
	After jetting	occurs	consume power
	the ink freezes	No wicking	Long warm-up
	almost instantly	occurs	time
	upon	No bleed
	contacting the	occurs
	print medium	No strike-
	or a transfer	through
	roller.	occurs
Oil	Oil based inks	High	High viscosity:	All IJ series
	are extensively	solubility	this is a	ink jets
	used in offset	medium for	significant
	printing.	some dyes	limitation for
	They have	Does not	use in ink jets,
	advantages in	cockle	which usually
	improved	paper	require a low
	characteristics	Does not	viscosity. Some
	on paper	wick	short chain and
	(especially no	through	multi-branched
	wicking or	paper	oils have a
	cockle). Oil		sufficiently
	soluble dies		low viscosity.
	and pigments		Slow drying
	are required.
Micro-	A micro-	Stops ink	Viscosity	All IJ series
emulsion	emulsion is a	bleed	higher than	ink jets
	stable, self	High dye	water
	forming	solubility	Cost is slightly
	emulsion of oil,	Water, oil,	higher than
	water, and	and	water based ink
	surfactant. The	amphiphilic	High surfactant
	characteristic	soluble	concentration
	drop size is	dies can	required
	less than	be used	(around 5%)
	100 nm, and is	Can
	determined by	stabilize
	the preferred	pigment
	curvature of	suspensions
	the surfactant.