The present invention relates to the field of ink jet printing systems.

Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invested. For a survey of the field. reference is made to an article by J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988).

Ink jet printers themselves come in many different types. The utilisation of a continuous stream ink in inkjet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

US Patent 3596275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)

Piezo-electric ink jet printers are also one form of commonly utilized ink jet printing device. Piezo-electric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilises a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezo electric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of picze-clectric operation, Howkins in US Patent No. 4459601 discloses a Piezo electric push mode actuation of the inkjet stream and Fischbeck in US 4584590 which discloses a sheer mode type of piezo-electric 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 US Patent 4490728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilising the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. JP55059972 describes an inkjet nozzle comprising a magnetic piston actuated by a coil. Ink is ejected by passing current through the coil, which urges the piston in a linear motion towards a nozzle opening. The piston functions as a magnetic pole.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.

Many inkjet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handing such precision devices often adds a substantially expense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Patent No. 4,899.181) are often used but again, this limit the amount of mass production throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilized. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S. Patent No. 5,208,604, micro-punching, etc.

The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.

It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.

It is an object of the present invention to provide for an ink jet printing mechanism having a series of ink ejection nozzles, with the nozzles including an internal selective actuator mechanism activated on a nozzle by nozzle basis by the placement of a field around said nozzles. Accordingly the invention provides an apparatus according to claim 1. Advantageous embodiments are provided in the dependent claims.

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

• Fig. 59 is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with an embodiment;
• Fig. 60 is a perspective view, in part in section, of a single ink jet nozzle constructed in accordance with an embodiment;
• Fig. 61 provides a legend of the materials indicated in Fig. 62 to Fig. 78; and
• Fig. 62 to Fig. 78 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.

The preferred embodiments and other embodiments will be discussed under separate headings with the heading including an IJ number for ease of reference. The headings also include a type designator with T indicating thermal, S indicating shutter type and F indicating a field type.

An embodiment of the present invention relies upon the utilisation of a magnetic actuator to "load" a spring, such that, upon deactivation of the magnetic actuator the resultant movement of the spring causes ejection of a drop of ink as the spring returns to its original position.

Turning to Fig. 59, there is illustrated an exploded perspective view of an ink nozzle arrangement 401 constructed in accordance with an embodiment. It would be understood that an embodiment can be constructed as an array of nozzle arrangements 401 so as to together form a line for printing.

The operation of the ink nozzle arrangement 401 of Fig. 59 proceeds by a solenoid 402 being energized by way of a driving circuit 403 when it is desired to print out a ink drop. The energized solenoid 402 induces a magnetic field in a fixed soft magnetic pole 404 and a moveable soft magnetic pole 405. The solenoid power is turned on to a maximum current for long enough to move the moveable pole 405 from its rest position to a stopped position close to the fixed magnetic pole 404. The ink nozzle arrangement 401 of Fig. 59 sits within an ink chamber filled with ink. Therefore, holes 406 are provided in the moveable soft magnetic pole 405 for "squirting" out of ink from around the coil 402 when the plate 405 undergoes movement.

The moveable soft magnetic pole is balanced by a fulcrum 408 with a piston head 409. Movement of the magnetic pole 405 closer to the stationary pole 404 causes the piston head 409 to move away from a nozzle chamber 411 drawing air into the chamber 411 via an ink ejection port 413. The piston 409 is then held open above the nozzle chamber 411 by means of maintaining a low "keeper" current through solenoid 402. The keeper level current through solenoid' 402 being sufficient to maintain the moveable pole 405 against the fixed soft magnetic pole 404. The level of current will be substantially less than the maximum current level because the gap between the two poles 404 and 405 is at a minimum. For example, a keeper level current of 10% of the maximum current level may be suitable. During this phase of operation, the meniscus of ink at the nozzle tip or ink ejection port 413 is a concave hemisphere due to the in flow of air. The surface tension on the meniscus exerts a net force on the ink which results in ink flow from the ink chamber into the nozzle chamber 411. This results in the nozzle chamber refilling, replacing the volume taken up by the piston head 409 which has been withdrawn. This process takes approximately 100 µs.

The current within solenoid 402 is then reversed to half that of the maximum current. The reversal demagnetizes the magnetic poles and initiates a return of the piston 409 to its rest position. The piston 409 is moved to its normal rest position by both the magnetic repulsion and by the energy stored in a stressed torsional spring 416,419 which was put in a state of torsion upon the movement of moveable pole 405.

The forces applied to the piston 409 as a result of the reverse current and spring 416,419 will be greatest at the beginning of the movement of the piston 409 and will decrease as the spring elastic stress falls to zero. As a result, the acceleration of piston 409 is high at the beginning of a reverse stroke and the resultant ink velocity within the chamber 411 becomes uniform during the stroke. This results in an increased operating tolerance before ink flow over the print head surface will occur.

At a predetermined time during the return stroke, the solenoid reverse current is turned off. The current is turned off when the residual magnetism of the movable pole is at a minimum. The piston 409 continues to move towards its original rest position.

The piston 409 will overshoot the quiescent or rest position due to its inertia. Overshoot in the piston movement achieves two things: greater ejected drop volume and velocity, and improved drop break off as the piston returns from overshoot to its quiescent position.

The piston 409 will eventually return from overshoot to the quiescent position. This return is caused by the springs 416, 419 which are now stressed in the opposite direction. The piston return "sucks" some of the ink back into the nozzle chamber 411, causing the ink ligament connecting the ink drop to the ink in the nozzle chamber 411 to thin. The forward velocity of the drop and the backward velocity of the ink in the nozzle chamber 411 are resolved by the ink drop breaking off from the ink in the nozzle chamber 411.

The piston 409 stays in the quiescent position until the next drop ejection cycle.

A liquid ink print head has one ink nozzle arrangement 401 associated with each of the multitude of nozzles. The arrangement 401 has the following major parts:

1. (1) Drive circuitry 403 for driving the solenoid 402.
2. (2) A nozzle tip 413. The radius of the nozzle tip 413 is an important determinant of drop velocity and drop size.
3. (3) A piston 404. This is a cylinder which moves through the nozzle chamber 411 to expel the ink. The piston 409 is connected to one end of the lever arm 417. The piston radius is approximately 1.5 to 2 times the radius of the hole 413. the ink drop volume output is mostly determined by the volume of ink displaced by the piston 409 during the piston return stroke.
4. (4) A nozzle chamber 411. The nozzle chamber 411 is slightly wider than the piston 409. The gap between the piston 409 and the nozzle chamber walls is as small as is required to ensure that the piston does not contact the nozzle chamber during actuation or return. If the print heads are fabricated using 0.5 µm semiconductor lithography, then a 1 µm gap will usually be sufficient. The nozzle chamber is also deep enough so that air ingested through the nozzle tip 413 when the plunger 409 returns to its quiescent state does not extend to the piston 409. If it does, the ingested bubble may form a cylindrical surface instead of a hemispherical surface. If this happens, the nozzle will not refill properly.
5. (5) A solenoid 402. This is a spiral coil of copper. Copper is used for its low resistivity, and high electro-migration resistance.
6. (6) A fixed magnetic pole of ferromagnetic material 404.
7. (7) A moveable magnetic pole of ferromagnetic material 405. To maximize the magnetic force generated, the moveable magnetic pole 405 and fixed magnetic pole 404 surround the solenoid 402 as a torus. Thus little magnetic flux is lost, and the flux is concentrated across the gap between the moveable magnetic pole 405 and the fixed pole 404. The moveable magnetic pole 405 has holes in the surface 406 (Fig. 59) above the solenoid to allow trapped ink to escape. These holes are arranged and shaped so as to minimize their effect on the magnetic force generated between the moveable magnetic pole 405 and the fixed magnetic pole 404.
8. (8) A magnetic gap. The gap between the fixed plate 404 and the moveable magnetic pole 405 is one of the most important "parts" of the print actuator. The size of the gap strongly affects the magnetic force generated, and also limits the travel of the moveable magnetic pole 405. A small gap is desirable to achieve a strong magnetic force. The travel of the piston 409 is related to the travel of the moveable magnetic pole 405 (and therefore the gap) by the lever arm 417.
9. (9) Length of the lever arm 417. The lever arm 417 allows the travel of the piston 409 and the moveable magnetic pole 405 to be independently optimized. At the short end of the lever arm 417 is the moveable magnetic pole 405. At the long end of the lever arm 417 is the piston 409. The spring 416 is at the fulcrum 408. The optimum travel for the moveable magnetic pole 405 is less than 1 micron, so as to minimize the magnetic gap. The optimum travel for the piston 409 is approximately 405 µm for a 1200 dpi printer. The difference in optimum travel is resolved by a lever 417 with a 5:1 or greater ratio in arm length.
10. (10) Springs 416, 419 (Fig. 59). The springs e.g. 416 return the piston to its quiescent position after a deactivation of the actuator. The springs 416 are at the fulcrum 408 of the lever arm.
11. (11) Passivation layers (not shown). Al surfaces are preferably coated with passivation layers, which may be silicon nitride (Si₃N₄), diamond like carbon (DLC), or other chemically inert, highly impermeable layer. The passivation layers are especially important for device lifetime, as the active device is immersed in the ink. As will be evident from the foregoing description there is an advantage in ejecting the drop on deactivation of the solenoid 402. This advantage comes from the rate of acceleration of the moving magnetic pole 405 which is used as a piston or plunger.

The force produced by a moveable magnetic pole by an electromagnetic induced field is approximately proportional to the inverse square of the gap between the moveable 405 and static magnetic poles 404. When the solenoid 402 is off, this gap is at a maximum. When the solenoid 402 is turned on, the moving pole 405 is attracted to the static pole 404. As the gap decreases, the force increases, accelerating the movable pole 405 faster. The velocity increases in a highly non-linear fashion, approximately with the square of time. During the reverse movement of the moving pole 405 upon deactivation the acceleration of the moving pole 405 is greatest at the beginning and then slows as the spring elastic stress falls to zero. As a result, the velocity of the moving pole 405 is more uniform during the reverse stroke movement.

1. (1) The velocity of piston or plunger 409 is much more constant over the duration of the drop ejection stroke.
2. (2) The piston or plunger 409 can readily be entirely removed from the ink chamber during the ink fill stage, and thereby the nozzle filling time can be reduced, allowing faster print head operation.

However, this approach does have some disadvantages over a direct firing type of actuator:

1. (1) The stresses on the spring 416 are relatively large. Careful design is required to ensure that the springs operate at below the yield strength of the materials used.
2. (2) The solenoid 402 must be provided with a "keeper" current for the nozzle fill duration. The keeper current will typically be less than 10% of the solenoid actuation current. However, the nozzle fill duration is typically around 50 times the drop firing duration, so the keeper energy will typically exceed the solenoid actuation energy.
3. (3) The operation of the actuator is more complex due to the requirement for a "keeper" phase.

The print head is fabricated from two silicon wafers. A first wafer is used to fabricate the print nozzles (the print head wafer) and a second wafer (the Ink Channel Wafer) is utilized to fabricate the various ink channels in addition to providing a support means for the first channel. The fabrication process then proceeds as follows:

• (1) Start with a single crystal silicon wafer 420, which has a buried epitaxial layer 422 of silicon which is heavity doped with boron. The boron should be doped to preferably 10²⁰ atoms per cm³ of boron or more, and be approximately 3 µm thick, and be doped in a manner suitable for the active semiconductor device technology chosen. The wafer diameter of the print head wafer should be the same as the ink channel wafer.
• (2) Fabricate the drive transistors and data distribution circuitry 403 according to the process chosen (e.g. CMOS).
• (3) Planarise the wafer 420 using chemical Mechanical Planarisation (CMP).
• (4) Deposit 5 micron of glass (SiO₂) over the second level metal.
• (5) Using a dual damascene process, etch two levels into the top oxide layer. Level 1 is 4 µm deep, and level 2 is 5 µm deep. Level 2 contacts the second level metal. The masks for the static magnetic pole are used.
• (6) Deposit 5 µm of nickel iron alloy (NiFe).
• (7) Planarise the wafer using CMP, until the level of the SiO₂ is reached forming the magnetic pole 404.
• (8) Deposit 0.1 µm of silicon nitride (Si₃N₄).
• (9) Etch the Si₃N₄ for via holes for the connections to the solenoids, and for the nozzle chamber region 411.
• (10) Deposit 4 µm of SiO₂.
• (11) Plasma etch the SiO₂ in using the solenoid and support post mask.
• (12) Deposit a thin diffusion barrier, such as Ti, TiN, or TiW, and an adhesion layer if the diffusion layer chosen has insufficient adhesion.
• (13) Deposit 4 µm of copper for forming the solenoid 402 and spring posts 424. The deposition may be by sputtering, CVD, or electroless plating. As well as lower resistivity than aluminum, copper has significantly higher resistance to electro-migration. The electro-migration resistance is significant, as current densities in the order of 3 x 10⁶ Amps/cm² may be required. Copper films deposited by low energy kinetic ion bias sputtering have been found to have 1,000 to 100,000 times larger electro-migration lifetimes larger than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration lifetimes than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration resistance, while maintaining high electrical conductivity.
• (14) Planarise the wafer using CMP, until the level of the SiO₂ is reached. A damascene process is used for the copper layer due to the difficulty involved in etching copper. However, since the damascene dielectric layer is subsequently removed, processing is actually simpler if a standard deposit/etch cycle is used instead of damascene. However, it should be noted that the aspect ratio of the copper etch would be 8:1 for this design, compared to only 4:1 for a damascene oxide etch. This difference occurs because the copper is 1 µm wide and 4 µm thick, but has only 0.5 µm spacing. Damascene processing also reduces the lithographic difficulty, as the resist is on oxide, not metal.
• (15) Plasma etch the nozzle chamber 411, stopping at the boron doped epitaxial silicon layer 421. This etch will be through around 13 µm of SiO₂, and 8 µm of silicon. The etch should be highly anisotropic, with near vertical sidewalls. The etch stop detection can be on boron in the exhaust gasses. If this etch is selective against NiFe, the masks for this step and the following step can be combined, and the following step can be eliminated. This step also etches the edge of the print head wafer down to the boron layer, for later separation.
• (16) Etch the SiO₂ layer. This need only be removed in the regions above the NiFe fixed magnetic poles, so it can be removed in the precious step if an Si and SiO₂ etch selective against NiFe is used.
• (17) Conformably deposit 0.5 µm of high density Si₃N₄. This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions.
• (18) Deposit a thick sacrificial layer 440. This layer should entirely fill the nozzle chambers, and coat the entire wafer to an added thickness of 8 µm. The sacrificial layer may be SiO₂.
• (19) Etch two depths in the sacrificial layer for a dual damascene process. The deep etch is 8 µm, and the shallow etch is 3 µm. The masks defines the piston 409, the lever arm 417, the springs 416 and the moveable magnetic pole 405.
• (20) Conformably deposit 0.1 µm of high density Si₃N₄. This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions.
• (21) Deposit 8 µm of nickel iron alloy (NiFe).
• (22) Planarise the wafer using CMP, until the level of the SiO₂ is reached.
• (23) Deposit 0.1 µm of silicon nitride (Si₃N₄).
• (24) Etch the Si₃N₄ everywhere except the top of the plungers.
• (25) Open the bond pads.
• (26) Permanently bond the wafer onto a pre-fabricated ink channel wafer. The active side of the print head wafer faces the ink channel wafer. The ink channel wafer is attached to a backing plate, as it has already been etched into separate ink channel chips.
• (27) Etch the print head wafer to entirely remove the backside silicon to the level of the boron doped epitaxial layer 422. This etch can be a batch wet etch in ethylenediamine pyrocatechol (EDP).
• (28) Mask the nozzle rim 414 from the underside of the print head wafer. This mask also includes the chip edges.
• (31) Etch through the boron doped silicon layer 422, thereby creating the nozzle holes. This etch should also etch fairly deeply into the sacrificial material in the nozzle chambers to reduce time required to remove the sacrificial layer.
• (32) Completely etch the sacrificial material. If this material is SiO₂ then a HF etch can be used. The nitride coating on the various layers protects the other glass dielectric layers and other materials in the device from HF etching. Access of the HF to the sacrificial layer material is through the nozzle, and simultaneously through the ink channel chip. The effective depth of the etch is 21 µm.
• (33) Separate the chips from the backing plate. Each chip is now a full print head including ink channels. The two wafers have already been etched through, so the print heads do not need to be diced.
• (34) Test the print heads and TAB bond the good print heads.
• (35) Hydrophobise the front surface of the print heads.
• (36) Perform final testing on the TAB bonded print heads.

Fig. 60 shows a perspective view, in part in section, of a single ink jet nozzle arrangement 401 constructed in accordance with an embodiment.

One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. 1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron.
2. 2. Deposit 10 microns of epitaxial silicon, either p-type or n-type, depending upon the CMOS process used.
3. 3. Complete a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in Fig. 62. For clarity, these diagrams may not be to scale, and may not represent a cross section through any single plane of the nozzle. Fig. 61 is a key to representations of various materials in these manufacturing diagrams.
4. 4. Etch the CMOS oxide layers down to silicon or aluminum using' Mask 1. This mask defines the nozzle chamber, the edges of the print heads chips, and the vias for the contacts from the aluminum electrodes to the two halves of the split fixed magnetic plate.
5. 5. Plasma etch the silicon down to the boron doped buried layer, using oxide from step 4 as a mask. This etch does not substantially etch the aluminum. This step is shown in Fig. 63.
6. 6. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)].
7. 7. Spin on 4 microns of resist, expose with Mask 2, and develop. This mask defines the split fixed magnetic plate and the nozzle chamber wall, for which the resist acts as an electroplating mold. This step is shown in Fig. 64.
8. 8. Electroplate 3 microns of CoNiFe. This step is shown in Fig. 65.
9. 9. Strip the resist and etch the exposed seed layer. This step is shown in Fig. 66.
10. 10. Deposit 0.1 microns of silicon nitride (Si₃N₄).
11. 11. Etch the nitride layer using Mask 3. This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic plate.
12. 12. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities.
13. 13. Spin on 5 microns of resist, expose with Mask 4, and develop. This mask defines the solenoid spiral coil, the nozzle chamber wall and the spring posts, for which the resist acts as an electroplating mold. This step is shown in Fig. 67.
14. 14. Electroplate 4 microns of copper.
15. 15. Strip the resist and etch the exposed copper seed layer. This step is shown in Fig. 68.
16. 16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.
17. 17. Deposit 0.1 microns of silicon nitride.
18. 18. Deposit 1 micron of sacrificial material. This layer determines the magnetic gap.
19. 19. Etch the sacrificial material using Mask 5. This mask defines the spring hosts and the nozzle chamber wall. This step is shown in Fig. 69.
20. 20. Deposit a seed layer of CoNiFe.
21. 21. Spin on 4.5 microns of resist, expose with Mask 6, and develop. Thins mask defines the walls of the magnetic plunger, the lever arm, the nozzle chamber wall and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in Fig. 70.
22. 22. Electroplate 4 microns of CoNiFe. This step is shown in Fig. 71.
23. 23. Deposit a seed layer of CoNiFe.
24. 24. Spin on 4 microns of resist, expose with Mask 7, and develop. This mask defines the roof of the magnetic plunger, the nozzle chamber wall, the lever arm, the springs, and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in Fig. 72.
25. 25. Electroplate 3 microns of CoNiFe. This step is shown in Fig. 73.
26. 26. Mount the wafer on a glass blank and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in Fig. 74.
27. 27. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask 8. This mask defines the nozzle rim. This step is shown in Fig. 75.
28. 28. Plasma back-etch through the boron doped layer using Mask 9. This mask defines the nozzle, and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in Fig. 76.
29. 29. Detach the chips from the glass blank. Strip all adhesive, resist, sacrificial, and exposed seed layers. This step is shown in Fig. 77.
30. 30. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer.
31. 31. Connect the print heads to their interconnect systems.
32. 32. Hydrophobize the front surface of the print heads.
33. 33. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 78.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: colour and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printer, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable colour and monochrome printers, colour and monochrome copiers, colour and monochrome facsimile machines, combined primer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic "minilabs", video printers, PhotoCD printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

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 inkjet 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 inkjet 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 inkjet 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 print head, but is a major impediment to the fabrication of pagewide print heads with 19,200 nozzles.

Ideally, the inkjet 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 inkjet 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 inkjet systems described below with differing levels of difficulty. 45 different inkjet 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.

The inkjet 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 print head is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the inkjet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the print head 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 print head is connected to the camera circuitry by tape automated bonding.

The following table is a guide to cross-referenced patent applications filed concurrently herewith and discussed hereinafter with the reference being utilized in subsequent tables when referring to a particular case: Docket No. Reference Title IJ01US IJ01 Radiant Plunger Ink Jet Printer IJ02US IJ02 Electrostatic Ink Jet Printer IJ03US IJ03 Planar Thermoelastic Bend Actuator Ink Jet IJ04US IJ04 Stacked Electrostatic Ink Jet Printer IJ05US IJ05 Reverse Spring Lever Ink Jet Printer IJ06US IJ06 Paddle Type Ink Jet Printer IJ07US IJ07 Permanent Magnet Electromagnetic Ink Jet Printer IJ08US IJ08 Planar Swing Grill Electromagnetic Ink Jet Printer IJ09US IJ09 Pump Action Refill Ink Jet Printer IJ10US IJ10 Pulsed Magnetic Field Ink Jet Printer IJ11US IJ11 Two Plate Reverse Firing Electromagnetic Ink Jet Printer IJ12US IJ12 Linear Stepper Actuator Ink Jet Printer IJ13US IJ13 Gear Driven Shutter Ink Jet Printer IJ14US IJ14 Tapered Magnetic Pole Electromagnetic Ink Jet Printer IJ15US IJ15 Linear Spring Electromagnetic Grill Ink Jet Printer IJ16US IJ16 Lorenz Diaphragm Electromagnetic Ink Jet Printer IJ17US IJ17 PTFE Surface Shooting Shuttered Oscillating Pressure Ink Jet Printer IJ18US IJ18 Buckle Grip Oscillating Pressure Ink Jet Printer IJ19US IJ19 Shutter Based Ink Jet Printer IJ20US IJ20 Curling Calyx Thermoelastic Ink Jet Printer IJ21US IJ21 Thermal Actuated Ink Jet Printer IJ22US IJ22 Iris Motion Ink Jet Printer IJ23US IJ23 Direct Firing Thermal Bend Actuator Ink Jet Printer IJ24US IJ24 Conductive PTFE Ben Activator Vented Ink Jet Printer IJ25US IJ25 Magnetostrictive Ink Jet Printer IJ26US IJ26 Shape Memory Alloy Ink Jet printer IJ27US IJ27 Buckle Plate Ink Jet Printer IJ28US IJ28 Thermal Elastic Rotary Impeller Ink Jet Printer IJ29US IJ29 Thermoelastic Bend Actuator Ink Jet Printer IJ30US IJ30 Thermoelastic Bend Actuator Using PTFE and Corrugated Copper Ink Jet Printer IJ31US IJ31 Bend Actuator Direct Ink Supply Ink Jet Printer IJ32US IJ32 A High Young's Modulus Thermoelastic Ink Jet Printer IJ33US IJ33 Thermally actuated slotted chamber wall ink jet printer IJ34US IJ34 Ink Jet Printer having a thermal actuator comprising an external coiled spring IJ35US IJ35 Trough Container Ink Jet Printer IJ36US IJ36 Dual Chamber Single Vertical Actuator Ink Jet IJ37US IJ37 Dual Nozzle Single Horizontal Fulcrum Actuator Ink Jet IJ38US IJ38 Dual Nozzle Single Horizontal Actuator Ink Jet IJ39US IJ39 A single bend actuator cupped paddle ink jet printing device IJ40US IJ40 A thermally actuated inkjet printer having a series of thermal actuator units IJ41US IJ41 A thermally actuated ink jet printer including a tapered heater element IJ42US IJ42 Radial Back-Curling Thermoelastic Ink Jet IJ43US IJ43 Inverted Radial Back-Curling Thermoelastic Ink Jet IJ44US IJ44 Surface bend actuator vented ink supply ink jet printer IJ45US IJ45 Coil Actuated Magnetic Plate Ink Jet Printer

Eleven important characteristics of the fundamental operation of individual inkjet 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 inkjet types.

• Actuator mechanism (18 types)
• Basic operation mode (7 types)
• Auxiliary mechanism (8 types)
• Actuator amplification or modification method (17 types)
• Actuator motion (19 types)
• Nozzle refill method (4 types)
• Method of restricting back-flow through inlet (10 types)
• Nozzle clearing method (9 types) .
• Nozzle plate construction (9 types)
• Drop ejection direction (5 types)
• Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of inkjet nozzle. While not all of the possible combinations result in a viable inkjet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain inkjet types have been investigated in detail. These are designated IJ01 to IJ45 above.

Other inkjet configurations can readily be derived from these 45 examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into inkjet print heads with characteristics superior to any currently available inkjet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a printer may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications 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 Description Advantages Disadvantages Examples Thermal bubble An electrothermal heater heats the ink to above boiling point, transferring significant heat to the aqueous ink. A bubble nucleates and quickly forms, expelling the ink.
The efficiency of the process is low, with typically less than 0.05°% of the electrical energy being transformed into kinetic energy of the drop. ◆ Large force generated,
◆ Simple construction
◆ No moving parts
◆ Fast operation
◆ Small chip area required
◆ for actuator ◆ High power
◆ Ink carrier limited to water
◆ Low efficiency
◆ High temperatures required High mechanical stress
◆ Unusual materials required
◆ Large drive transistors
◆ Cavitation causes actuator failure
◆ Kogation reduces bubble formation
◆ Large print heads are difficult to fabricate ◆ Canon Bubblejet 1979 Endo et al GB patent 2,007,162
◆ Xerox heater-in-pit 1990 Hawkins et al USP 4,899,181
◆ Hewlett-Packard TIJ 1982 Vaught et al USP 4,490,728 Piezoelectric A piezoelectric crystal such as lead lanthanum zirconate (PZT) is electrically activated, and either expands, shears, or bends to apply pressure to the ink, ejecting drops. ◆ Low power consumption
◆ Many ink types can be used
◆ Fast operation
◆ High efficiency ◆ Very large area required for actuator
◆ Difficult to integrate with electronics
◆ High voltage drive transistors required
◆ Full pagewidth print heads impractical due to actuator size
◆ Requires electrical poling in high field strengths during manufacture ◆ Kyser et al USP 3,946,398
◆ Zoltan USP 3,683,212
◆ 1973 Stemme USP 3,747,120
◆ Epson Stylus
◆ Tektronix
◆ IJ04 Electro-strictive An electric field is used to activate electrostriction in relaxor materials such as lead lanthanum zirconate titanate (PLZT) or lead magnesium niobate (PMN). ◆ Low power consumption
◆ Many ink types can be used
◆ Low thermal expansion
◆ Electric field strength required (approx. 3.5 V/µm) can be generated without difficulty
◆ Does not require electrical poling ◆ Low maximum strain (approx. 0.01%)
◆ Large area required for actuator due to low strain
◆ Response speed is marginal (~ 10 µs)
◆ High voltage drive transistors required
◆ Full pagewidth print heads impractical due to actuator size ◆ Seiko Epson, Usui et all JP 253401/96
◆ IJ04 Ferroelectric An electric field is used to induce a phase transition between the antiferroelectric (AFE) and ferroelectric (FE) phase.
Perovskite materials such as tin modified lead lanthanum zirconate titanate (PLZSnT) exhibit large strains of up to 1% associated with the AFE to FE phase transition. ◆ Low power consumption
◆ Many ink types can be used
◆ Fast operation (< 1 µs)
◆ Relatively high longitudinal strain
◆ High efficiency Electric field strength of around 3 V/µm can be readily provided ◆ Difficult to integrate with electronics
◆ Unusual materials such as PLZSnT are required
◆ Actuators require a large area ◆ IJ04 Electrostatic: plates Conductive plates are separated by a compressible or fluid dielectric (usually air). Upon application of a voltage, the plates attract each other and displace ink, causing drop ejection. The conductive plates may be in a comb or honeycomb structure, or stacked to increase the surface area and therefore the force. ◆ Low power consumption
◆ Many ink types can be used
◆ Fast operation ◆ Difficult to operate electrostatic devices in an aqueous environment
◆ The electrostatic actuator will normally need to be separated from the ink
◆ Very large area required to achieve high forces
◆ High voltage drive transistors may be required
◆ Full pagewidth print heads are not competitive due to actuator size ◆ IJ02, IJ04 Electrostatic pull on ink A strong electric field is applied to the ink, whereupon electrostatic attraction accelerates the ink towards the print medium. ◆ Low current consumption
◆ Low temperature ◆ High voltage required
◆ May be damaged by sparks due to air breakdown
◆ Required field strength increases as the drop size decreases High voltage drive transistors required
◆ Electrostatic field attracts dust ◆ 1989 Saito et al, USP 4,799,068
◆ 1989 Miura et al, USP 4,810,954
◆ Tone-jet Permanent magnet electro- magnetic An electromagnet directly attracts a permanent magnet, displacing ink and causing drop ejection. Rare earth magnets with a field strength around 1 Tesla can be used. Examples are: Samarium Cobalt (SaCo) and magnetic materials in the neodymium iron boron family (NdFeB, NdDyFeBNb, NdDyFeB, etc) ◆ Low power consumption
◆ Many ink types can be used
◆ Fast operation
◆ High efficiency
◆ Easy extension from single nozzles to pagewidth print heads ◆ Complex fabrication
◆ Permanent magnetic material such as Neodymium Iron Boron (NdFeB) required.
◆ High local currents required
◆ Copper metalization should be used for long electromigration lifetime and low resistivity
◆ Pigmented inks are usually infeasible
◆ Operating temperature limited to the Curie temperature (around 540 K) ◆ IJ07, IJ10 Soft magnetic core electro-magnetic A solenoid induced a magnetic field in a soft magnetic core or yoke fabricated from a ferrous material such as electroplated iron alloys such as CoNiFe [1], CoFe, or NiFe alloys. Typically, the soft magnetic material is in two parts, which are normally held apart by a spring. When the solenoid is actuated, the two parts attract, displacing the ink. ◆ Low power consumption
◆ Many ink types can be used
◆ Fast operation
◆ High efficiency
◆ Easy extension from single nozzles to pagewidth print heads ◆ Complex fabrication
◆ Materials not usually present in a CMOS fab such as NiFe, CoNlFe, or CoFe are required
◆ High local currents required
◆ Copper metalization should be used for long electromigration lifetime and low resistivity
◆ Electroplating is required
◆ High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) ◆ IJ01, IJ05, IJ08, IJ10
◆ IJ12, IJ14, IJ15, IJ17 Magnetic Lorenz force The Lorenz force acting on a current carrying wire in a magnetic field is utilized. This allows the magnetic field to be supplied externally to the print head, for example with rare earth permanent magnets.
Only the current carrying wire need be fabricated on the print-head, simplifying materials requirements. ◆ Low power consumption
◆ Many ink types can be ◆ used
◆ Fast operation
◆ High efficiency
◆ Easy extension from single nozzles to pagewidth print heads ◆ Force acts as a twisting motion
◆ Typically, only a quarter of the solenoid length provides force in a useful direction
◆ High local currents required
◆ Copper metalization should be used for long electromigration lifetime and low resistivity
◆ Pigmented inks are usually infeasible ◆ IJ06, IJ11, IJ13, IJ16 Magneto-striction The actuator uses the giant magnetostrictive effect of materials such as Terfenol-D (an alloy of terbium, dysprosium and iron developed at the Naval Ordnance Laboratory, hence Ter-Fe-NOL). For best efficiency, the actuator should be pre-stressed to approx. 8 MPa. ◆ Many ink types can be used
◆ Fast operation
◆ Easy extension from single nozzles to pagewidth print heads
◆ High force is available ◆ Force acts as a twisting motion
◆ Unusual materials such as Terfenol-D are required
◆ High local currents required
◆ Copper metalization should be used for long electromigration lifetime and low resistivity
◆ Pre-stressing may be required ◆ Fischenbeck, USP 4,032,929
◆ IJ25 Surface tension reduction Ink under positive pressure is held in a nozzle by surface tension. The surface tension of the ink is reduced below the bubble threshold, causing the ink to egress from the nozzle. ◆ Low power consumption
◆ Simple construction
◆ No unusual materials required in fabrication
◆ High efficiency
◆ Easy extension from single nozzles to pagewidth print heads ◆ Requires supplementary force to effect drop separation
◆ Requires special ink surfactants
◆ Speed may be limited by surfactant properties ◆ Silverbrook, EP 0771 658 A2 and related patent applications Viscosity reduction The ink viscosity is locally reduced to select which drops are to be ejected. A viscosity reduction can be achieved electrothermally with most inks, but special inks can be engineered for a 100:1 viscosity reduction. ◆ Simple construction
◆ No unusual materials required in fabrication
◆ Easy extension from single nozzles to pagewidth print heads ◆ Requires supplementary force to effect drop separation
◆ Requires special ink viscosity properties
◆ High speed is difficult to achieve
◆ Requires oscillating ink pressure
◆ A high temperature difference (typically 80 degrees) is required ◆ Silverbrook, EP 0771 658 A2 and related patent applications Acoustic An acoustic wave is generated and focussed upon the drop ejection region. ◆ Can operate without a nozzle plate ◆ Complex drive circuitry
◆ Complex fabrication
◆ Low efficiency
◆ Poor control of drop position
◆ Poor control of drop volume ◆ 1993 Hadimioglu et al, EUP 550,192
◆ 1993 Elrod et al, EUP 572,220 Thermoelastic bend actuator An actuator which relies upon differential thermal expansion upon Joule heating is used. ◆ Low power consumption
◆ Many ink types can be used
◆ Simple planar fabrication
◆ Small chip area required for each actuator
◆ Fast operation
◆ High efficiency
◆ CMOS compatible voltages and currents
◆ Standard MEMS processes can be used
◆ Easy extension from single nozzles to pagewidth print heads ◆ Efficient aqueous operation requires a thermal insulator on the hot side
◆ Corrosion prevention can be difficult
◆ Pigmented inks may be infeasible, as pigment particles may jam the bend actuator ◆ IJ03, IJ09, IJ17, IJ18
◆ IJ19, IJ20, IJ21, IJ22
◆ IJ23, IJ24, IJ27, IJ28
◆ IJ29, IJ30, IJ31, IJ32
◆ IJ33, IJ34, IJ35, IJ36
◆ IJ37, IJ38 ,IJ39, IJ40
◆ IJ41 High CTE thermoelastic actuator A material with a very high coefficient of thermal expansion (CTE) such as polytetrafluoroethylene (PTFE) is used. As high CTE materials are usually non-conductive, a heater fabricated from a conductive material is incorporated. A 50 µm long PTFE bend actuator with polysilicon heater and 15 mW power input can provide 180 µN force and 10 µm deflection. Actuator motions include:
1) Bend
2) Push
3) Buckle
4) Rotate ◆ High force can be generated
◆ PTFE is a candidate for low dielectric constant insulation in ULSI
◆ Very low power consumption
◆ Many ink types can be used
◆ Simple planar fabrication
◆ Small chip area required for each actuator
◆ Fast operation
◆ High efficiency
◆ CMOS compatible voltages and currents
◆ Easy extension from single nozzles to pagewidth print heads ◆ Requires special material (e.g. PTFE)
◆ Requires a PTFE deposition process, which is not yet standard in ULSI fabs
◆ PTFE deposition cannot be followed with high temperature (above 350 °C) processing
◆ Pigmented inks may be infeasible, as pigment particles may jam the bend actuator ◆ IJ09, IJ17, IJ18, IJ20
◆ IJ21, IJ22, IJ23, IJ24
◆ IJ27, IJ28, IJ29, IJ30
◆ IJ31, IJ42, IJ43, IJ44 Conductive polymer thermoelastic actuator A polymer with a high coefficient of thermal expansion (such as PTFE) is doped with conducting substances to increase its conductivity to about 3 orders of magnitude below that of copper. The conducting polymer expands when resistively heated. each Examples of conducting dopants include:
1) Carbon nanotubes
2) Metal fibers
3) Conductive polymers such as doped polythiophene
4) Carbon granules ◆ High force can be generated
◆ Very low power consumption
◆ Many ink types can be used
◆ Simple planar fabrication
◆ Small chip area required for actuator
◆ Fast operation
◆ High efficiency
◆ CMOS compatible voltages and currents
◆ Easy extension from single nozzles to pagewidth print heads ◆ Requires special materials development (High CTE conductive polymer)
◆ Requires a PTFE deposition process, which is not yet standard in ULSI fabs
◆ PTFE deposition cannot be followed with high temperature (above 350 °C) processing
◆ Evaporation and CVD deposition techniques cannot be used
◆ Pigmented inks may be infeasible, as pigment particles may jam the bend actuator ◆ IJ24 Shape memory alloy A shape memory alloy such as TiNi (also known as Nitinol - Nickel Titanium alloy developed at the Naval Ordnance Laboratory) is thermally switched between its weak martensitic state and its high stiffness austenic state. The shape of the actuator in its martensitic state is deformed relative to the austenic shape. The shape change causes ejection of a drop. ◆ High force is available (stresses of hundreds of MPa)
◆ Large strain is available (more than 3%)
◆ High corrosion resistance
◆ Simple construction
◆ Easy extension from single nozzles to pagewidth print heads
◆ Low voltage operation ◆ Fatigue limits maximum number of cycles
◆ Low strain (1%) is required to extend fatigue resistance
◆ Cycle rate limited by heat removal
◆ Requires unusual materials (TiNi)
◆ The latent heat of transformation must be provided
◆ High current operation
◆ Requires pre-stressing to distort the martensitic state ◆ IJ26 Linear Magnetic Actuator Linear magnetic actuators include the Linear Induction Actuator (LIA), Linear Permanent Magnet Synchronous Actuator (LPMSA), Linear Reluctance Synchronous Actuator (LRSA), Linear Switched Reluctance Actuator (LSRA), and the Linear Stepper Actuator (LSA). ◆ Linear Magnetic actuators can be constructed with high thrust, long travel, and high efficiency using planar semiconductor fabrication techniques
◆ Long actuator travel is available
◆ Medium force is available
◆ Low voltage operation ◆ Requires unusual semiconductor materials such as soft magnetic alloys (e.g. CoNiFe [1])
◆ Some varieties also require permanent magnetic materials such as Neodymium iron boron (NdFeB)
◆ Requires complex multi-phase drive circuitry
◆ High current operation ◆ IJ12

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

Auxiliary Mechanism Description Advantages Disadvantages Examples None The actuator directly fires the ink drop, and there is no external field or other mechanism required. ◆ Simplicity of construction
◆ Simplicity of operation
◆ Small physical size ◆ Drop ejection energy must be supplied by individual nozzle actuator ◆ Most inkjets, including piezoelectric and thermal bubble.
◆ IJ01-IJ07, IJ09, IJ11
◆ IJ12, IJ14, IJ20, IJ22
◆ IJ23-IJ45 Oscillating ink pressure (including acoustic stimulation) The ink pressure oscillates, providing much of the drop ejection energy. The actuator selects which drops are to be fired by selectively blocking or enabling nozzles. The ink pressure oscillation may be achieved by vibrating the print head, or preferably by an actuator in the ink supply. ◆ Oscillating ink pressure can provide a refill pulse, allowing higher operating speed
◆ The actuators may operate with much lower energy
◆ Acoustic lenses can be used to focus the sound on the nozzles ◆ Requires external ink pressure oscillator
◆ Ink pressure phase and amplitude must be carefully controlled
◆ Acoustic reflections in the ink chamber must be designed for ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ IJ08, IJ13, IJ15, IJ17
◆ IJ18, IJ19, IJ21 Media proximity The print head is placed in close proximity to the print medium. Selected drops protrude from the print head further than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. ◆ Low power
◆ High accuracy
◆ Simple print head construction ◆ Precision assembly required
◆ Paper fibers may cause problems
◆ Cannot print on rough substrates ◆ Silverbrook, EP 0771 658 A2 and related patent applications Transfer roller Drops are printed to a transfer roller instead of straight to the print medium. A transfer roller can also be used for proximity drop separation. ◆ High accuracy
◆ Wide range of print substrates can be used
◆ Ink can be dried on the transfer roller ◆ Bulky
◆ Expensive
◆ Complex construction ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ Tektronix hot melt piezoelectric inkjet
◆ Any of the IJ series Electrostatic An electric field is used to accelerate selected drops towards the print medium. ◆ Low power
◆ Simple print head construction ◆ Field strength required for separation of small drops is near or above air breakdown ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ Tone-Jet Direct magnetic field A magnetic field is used to accelerate selected drops of magnetic ink towards the print medium. ◆ Low power
◆ Simple print head construction ◆ Requires magnetic ink
◆ Requires strong magnetic field ◆ Silverbrook, EP 0771 658 A2 and related patent applications Cross magnetic field The print head is placed in a constant magnetic field. The Lorenz force in a current carrying wire is used to move the actuator. ◆ Does not require magnetic materials to be integrated in the print head manufacturing process ◆ Requires external magnet
◆ Current densities may be high, resulting in electromigration problems ◆ IJ06, IJ16 Pulsed magnetic field A pulsed magnetic field is used to cyclically attract a paddle, which pushes on the ink. A small actuator moves a catch, which selectively prevents the paddle from moving. ◆ Very low power operation is possible
◆ Small print head size ◆ Complex print head construction
◆ Magnetic materials required in print head ◆ IJ10

Actuator amplification Description Advantages Disadvantages Examples None No actuator mechanical amplification is used. The actuator directly drives the drop ejection process. ◆ Operational simplicity ◆ Many actuator mechanisms have insufficient travel, or insufficient force, to efficiently drive the drop ejection process ◆ Thermal Bubble Inkjet
◆ IJ01, IJ02, IJ06, IJ07
◆ IJ16, IJ25, IJ26 Differential expansion bend actuator An actuator material expands more on one side than on the other. The expansion may be thermal, piezoelectric, magnetostrictive, or other mechanism. ◆ Provides greater travel in a reduced print head area
◆ The bend actuator converts a high force low travel actuator mechanism to high travel, lower force mechanism. ◆ High stresses are involved
◆ Care must be taken that the materials do not delaminate
◆ Residual bend resulting from high temperature or high stress during formation ◆ Piezoelectric
◆ IJ03, IJ09, IJ17-IJ24
◆IJ27, IJ29-IJ39, IJ42,
◆ IJ43, IJ44 Transient bend actuator A trilayer bend actuator where the two outside layers are identical. This cancels bend due to ambient temperature and residual stress. The actuator only responds to transient heating of one side or the other. ◆ Very good temperature stability
◆ High speed, as a new drop can be fired before heat dissipates
◆ Cancels residual stress of formation ◆ High stresses are involved
◆ Care must be taken that the materials do not delaminate ◆ IJ40, IJ41 Actuator stack A series of thin actuators are stacked. This can be appropriate where actuators require high electric field strength, such as electrostatic and piezoelectric actuators. ◆ Increased travel
◆ Reduced drive voltage ◆ Increased fabrication complexity
◆ Increased possibility of short circuits due to pinholes ◆ Some piezoelectric ink jets
◆ IJ04 Multiple actuators Multiple smaller actuators are used simultaneously to move the ink. Each actuator need provide only a portion of the force required. ◆ Increases the force available from an actuator
◆ Multiple actuators can be positioned to control ink flow accurately ◆ Actuator forces may not add linearly, reducing efficiency ◆ IJ12, IJ13, IJ18, IJ20
◆ IJ22, IJ28, IJ42, IJ43 Linear Spring A linear spring is used to transform a motion with small travel and high force into a longer travel, lower force motion. ◆ Matches low travel actuator with higher travel requirements
◆ Non-contact method of motion transformation ◆ Requires print head area for the spring ◆ IJ15 Reverse spring The actuator loads a spring. When the actuator is 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 section. ◆ Better coupling to the ink ◆ Fabrication complexity
◆ High stress in the spring ◆ IJ05, IJ11 Coiled actuator A band actuator is coiled to provide greater travel in a reduced chip area. ◆ Increases travel
◆ Reduces chip area
◆ Planar implementations are relatively easy to fabricate. ◆ Generally restricted to planar implementations due to extreme fabrication difficulty in other orientations. ◆ IJ17, IJ21, IJ34, IJ35 Flexure bend actuator A bend actuator has a small region near the fixture point, which flexes much more readily than the remainder of the actuator.
The actuator flexing is effectively converted from an even coiling to an angular bend, resulting in greater travel of the actuator tip. ◆ Simple means of increasing travel of a bend actuator ◆ Care must be taken not to exceed the elastic limit in the flexure area
◆ Stress distribution is very uneven
◆ Difficult to accurately model with finite element analysis ◆ IJ10, IJ19, IJ33 Gears Gears can be used to increase travel at the expense of duration. Circular gears, rack and pinion, ratchets, and other gearing methods can be used. ◆ Low force, low travel actuators can be used
◆ Can be fabricated using standard surface MEMS processes ◆ Moving parts are required
◆ Several actuator cycles are required
◆ More complex drive electronics
◆ Complex construction
◆ Friction, friction, and wear are possible ◆ IJ13 Catch The actuator controls a small catch. The catch either enables or disables movement of an ink pusher that is controlled in a bulk manner. ◆ Very low actuator energy
◆ Very small actuator size ◆ Complex construction
◆ Requires external force
◆ Unsuitable for pigmented inks ◆ IJ10 Buckle plate A buckle plate can be used to change a slow actuator into a fast motion. It can also convert a high force, low travel actuator into a high travel, medium force motion. ◆ Very fast movement achievable ◆ Must stay within elastic limits of the materials for long device life
◆ High stresses involved
◆ Generally high power ◆ S. Hirata et al, "An Ink-jet Head ...", Proc. IEEE requirement MEMS, Feb. 1996, pp 418- 423.
◆ IJ18, IJ27 Tapered magnetic pole A tapered magnetic pole can increase travel at the expense of force. ◆ Linearizes the magnetic force/distance curve ◆ Complex construction ◆ IJ14 Lever A lever and fulcrum is used to transform a motion with small travel and high force into a motion with longer travel and lower force. The lever can also reverse the direction of travel. ◆ Matches low travel actuator with higher travel requirements
◆ Fulcrum area has no linear movement, and can be used for a fluid seal ◆ High stress around the fulcrum ◆ IJ32, IJ36, IJ37 Rotary impeller The actuator is connected to a rotary impeller. A small angular deflection of the actuator results in a rotation of the impeller vanes, which push the ink against stationary vanes and out of the nozzle. ◆ High mechanical advantage
◆ The ratio of force to travel of the actuator can be matched to the nozzle requirements by varying the number of impeller vanes ◆ Complex construction
◆ Unsuitable for pigmented inks ◆ IJ28 Acoustic lens A refractive or diffractive (e.g. zone plate) acoustic lens is used to concentrate sound waves. ◆ No moving parts ◆ Large area required
◆ Only relevant for acoustic ink jets ◆ 1993 Hadimioglu et al. EUP 550,192
◆ 1993 Elrod et al. EUP 572,220 Sharp conductive points A sharp point is used to concentrate an' electrostatic field. ◆ Simple construction ◆ Difficult to fabricate using standard VLSI processes for a surface ejecting ink-jet
◆ Only relevant for electrostatic ink jets ◆ Tone-jet

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

Nozzle refill method Description Advantages Disadvantages Examples Surface tension After the actuator is energized, it typically returns rapidly to its normal position. This rapld return 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. ◆ Fabrication simplicity
◆ Operational simplicity ◆ Low speed
◆ Surface tension force relatively small compared to actuator force
◆ Long refill time usually dominates the total repetition rate ◆ Thermal inkjet
◆ Piezoelectric inkjet
◆ IJ01-IJ07,IJ10-IJ14
◆ IJ16 IJ20, IJ22-IJ45 Shuttered oscillating ink pressure Ink to the nozzle chamber is provided at a pressure that oscillates at twice the drop ejection frequency. When a drop is to be ejected, the shutter is opened for 3 half cycles: drop ejection, actuator return, and refill. ◆ High speed
◆ Low actuator energy, as the actuator need only open or for close the shutter, instead ofejecting the ink drop ◆ Requires common ink pressure oscillator
◆ May not be suitable pigmented inks ◆ IJ08,IJ13,IJ15,IJ17
◆ IJ18, IJ19, IJ21 Refill actuator After the main actuator has ejected a drop a second (refill) 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. ◆ High speed, as the nozzle is actively refilled ◆ Requires two independent actuator per nozzle ◆ IJ09 Positive ink pressure The ink is held a slight positive pressure. After the ink drop is ejected, the nozzle chamber fills quickly as surface tension and ink pressure both operate to refill the nozzle. ◆ High refill rate, therefore a high drop repetition rate is possible ◆ Surface spill must be prevented
◆ Highly hydrophobic print head surfaces are required ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ Alternative for:
◆ IJ01-IJ07, IJ10-IJ14
◆ IJ16, IJ20, IJ22-IJ45

Inlet back-flow restriction method Description Advantages Disadvantages Examples Long inlet channel The ink inlet channel to the nozzle chamber is made long and relatively narrow, relying on viscous drag to reduce inlet back-flow. ◆ Design simplicity
◆ Operational simplicity
◆ Reduces crosstalk ◆ Restricts refill rate
◆ May result in a relatively large chip area
◆ Only partially effective ◆ Thermal inkjet
◆ Piezoelectric inkjet
◆ IJ42, IJ43 Positive ink pressure The ink is under a positive pressure, so that in the quiescent state some of the ink drop already protrudes from the nozzle.
This reduces the pressure in the nozzle chamber which is required to eject a certain volume of ink. The reduction in chamber pressure results in a reduction in ink pushed out through the ◆ Drop selection and separation forces can be reduced
◆ Fast refill time ◆ Requires a method (such as a nozzle rim or effective hydrophobizing, or both) to prevent flooding of the ejection surface of the print head. ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ Possible operation of the following:
◆ IJ01-IJ07, IJ09- IJ12
◆ IJ14, IJ16, IJ20, IJ22, inlet.
◆ IJ23-IJ34, IJ36-IJ41
◆ IJ44 Baffle One or more baffles are placed in the inlet ink flow. When the actuator is energized, the rapid ink movement creates eddies which restrict the flow through the inlet.
The slower refill process is unrestricted, and does not result in eddies. ◆ The refill rate is not as restricted as the inlet method.
◆ Reduces crosstalk ◆ Design complexity long
◆ May increase fabrication complexity (e.g. Tektronix hot melt Piezoelectric print heads). ◆ HP Thermal Ink Jet
◆ Tektronix piezoelectric ink jet Flexible flap restricts inlet In this method recently disclosed by Canon, the expanding actuator (bubble) pushes on a flexible flap that restricts the inlet^.. ◆ Significantly reduces back-flow for edge-shooter thermal ink jet devices ◆ Not applicable to most inkjet configurations
◆ Increased fabrication complexity
◆ Inelastic deformation of polymer flap results in creep over extended use ◆ Canon Inlet filter A filter is located between the ink inlet and the nozzle chamber. The filter has a multitude of small holes or slots, restricting ink flow. The filter also removes particles which may block the nozzle. ◆ Additional advantage of ink filtration
◆ Ink filter may be fabricated with no additional process steps ◆ Restricts refill rate ◆ May result in complex construction ◆ IJ04, IJ12, IJ24, IJ27
◆ IJ29, IJ30 Small inlet compared to nozzle The ink inlet channel to the nozzle chamber has a substantially smaller cross section than that of the nozzle, resulting in easier ink egress out of the nozzle than out of the inlet. ◆ Design simplicity ◆ Restricts refill rate
◆ May result in a relatively large chip area
◆ Only partially effective ◆ IJ02, IJ37, IJ44 Inlet shutter A secondary actuator controls the position of a shutter, closing off the ink inlet when the main actuator is energized. ◆ Increases speed of the ink-Jet print head operation ◆ Requires separate refill actuator and drive circuit ◆ IJ09 The inlet is located behind the ink-pushing surface The method avoids the problem of inlet back-flow by arranging the ink-pushing surface of the actuator between the inlet and the nozzle. ◆ Back-flow problem is eliminated ◆ Requires careful design to minimize the negative pressure behind the paddle ◆ IJ01, IJ03, IJ05, IJ06
◆ IJ07, IJ10, IJ11, IJ14
◆ IJ16, IJ22, IJ23, IJ25
◆ IJ28, IJ31, IJ32, IJ33
◆ IJ34, IJ35, IJ36, IJ39
◆ IJ40, IJ41 Part of the actuator moves to shut off the inlet The actuator and a wall of the ink chamber are arranged so that the motion of the actuator closes off the inlet. ◆ Significant reductions in back-flow can be achieved
◆ Compact designs possible ◆ Small increase in fabrication complexity ◆ IJ07, IJ20, IJ26, IJ38 Nozzle actuator does not result In Ink back-flow In some configurations of ink jet, there is no expansion or movement of an actuator which may cause ink back-flow through the inlet. ◆ Ink back-flow problem is eliminated ◆ None related to ink back-flow on actuation ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ Valve-jet
◆ Tone-jet
◆ IJ08, IJ13, IJ15, IJ17,
◆ IJ18, IJ19, IJ21

Nozzle Clearing method Description Advantages Disadvantages Examples Normal nozzle firing All of the nozzles are fired periodically, before the ink has a chance to dry. When not in use the nozzles are sealed (capped) against air.
The nozzle firing is usually performed during a special clearing cycle, after first moving the print head to a cleaning station. ◆ No added complexity on the print head ◆ May not be sufficient to displace dried ink ◆ Most ink jet systems
◆ IJ01- IJ07, IJ09-IJ12
◆ IJ14, IJ16, IJ20, IJ22
◆ IJ23- IJ34, IJ36-IJ45 Extra power to ink heater In systems which heat the ink, but do not boil it under normal situations, nozzle clearing can be achieved by over-powering the heater and boiling ink at the nozzle. ◆ Can be highly effective if the heater is adjacent to the nozzle ◆ Requires higher drive voltage for clearing
◆ May require larger drive transistors ◆ Silverbrook, EP 0771 658 A2 and related patent applications Rapid succession of actuator pulses The actuator is fired in rapid succession. In some configurations, this may cause heat build-up at the nozzle which bolls the ink, clearing the nozzle. In other situations, it may cause sufficient vibrations to dislodge clogged nozzles. ◆ Does not require extra drive circuits on the print head
◆ Can be readily controlled and initiated by digital logic ◆ Effectiveness depends substantially upon the configuration of the inkjet nozzle ◆ May be used with:
◆ IJ01-IJ07, IJ09-IJ11
◆ IJ14, IJ16, IJ20, IJ22
◆ IJ23-IJ25, IJ27-U34
◆ IJ36-IJ45 Extra power to ink pushing actuator Where an actuator is not normally driven to the limit of its motion, nozzle clearing may be assisted by providing an enhanced drive signal to the actuator. ◆ A simple solution where applicable Not suitable where there is a hard limit to actuator movement ◆ May be used with:
◆ IJ03, IJ09, IJ16 IJ20
◆ IJ23, IJ24, IJ25, IJ27
◆ IJ29, IJ30, IJ31, IJ32
◆ IJ39, IJ40, IJ41, IJ42
◆ IJ43, IJ44, IJ45 Acoustic resonance An ultrasonic wave is applied to the ink chamber. This wave is ofan appropriate amplitude and frequency to cause sufficient force at the nozzle to clear blockages. This is easiest to achieve if the ultrasonic wave is at a resonant frequency of the ink cavity. ◆ A high nozzle clearing capability can be achieved
◆ May be implemented at very low cost in systems which already include acoustic actuators ◆ High implementation cost if system does not already include an acoustic actuators ◆ IJ08, IJ13, IJ15, IJ17
◆ IJ18, IJ19, IJ21 Nozzle clearing plate A microfabricated plate is pushed against the nozzles. The plate has a post for every nozzle. The array of posts ◆ Can clear severely clogged nozzles ◆ Accurate mechanical alignment is required
◆ Moving parts are required
◆ There is risk of damage to the nozzles
◆ Accurate fabrication is required ◆ Silverbrook, EP 0771 658 A2 and related patent applications Ink pressure pulse The pressure of the ink is temporarily increased so that ink streams from all of the nozzles. This may be used in conjunction with actuator energizing. ◆ May be effective where other methods cannot be used ◆ Requires pressure pump or other pressure actuator
◆ Expensive
◆ Wasteful of ink ◆ May be used with all IJ series ink jets Print head wiper A flexible 'blade' is wiped across the print head surface. The blade is usually fabricated from a flexible polymer, e.g. rubber or synthetic elastomer. ◆ Effective for planar print head surfaces
◆ Low cost ◆ Difficult to use if print head surface is non-planar or very fragile
◆ Requires mechanical parts
◆ Blade can wear out in high volume print systems ◆ Many ink jet systems Separate ink boiling heater A separate heater is provided at the nozzle although the normal drop e-ection mechanism does not require it. The heaters do not require individual drive circuits, as many nozzles can be cleared simultaneously, and no imaging is required. ◆ Can be effective where other nozzle clearing methods cannot be used
◆ Can be implemented at no additional cost in some inkjet configurations ◆ Fabrication complexity ◆ Can be used with many IJseries ink Jets

Nozzle plate construction Description Advantages Disadvantages Examples Electroformed nickel A nozzle plate is separately fabricated from electroformed nickel, and bonded to the print head chip. ◆ Fabrication simplicity ◆ High temperatures and pressures are required to bond nozzle plate
◆ Minimum thickness constraints
◆ Differential thermal expansion ◆ Hewlett Packard Thermal Inkjet Laser ablated or drilled polymer Individual nozzles holes are ablated by an intense UV laser in a nozzle plate, which is typically a polymer such as polyimide or polysulphone ◆ No masks required
◆ Can be quite fast ◆ Some control over nozzle profile is possible
◆ Equipment required is relatively low cost ◆ Each hole must be individually formed
◆ Special equipment required
◆ Slow where there are many thousands of nozzles per print head
◆ May produce thin burrs at exit holes ◆ Canon Bubblejet
◆ 1988 Sercel et al., SPIE, Vol. 998 Excimer Beam Applications, pp 76-83 .
◆ 1993 Watanabe et al., USP 5,208,604 Silicon micro-machined A separate nozzle plate is micromachined from single crystal silicon, and bonded to the print head wafer. ◆ High accuracy is attainable ◆ Two part construction
◆ High cost
◆ Requires precision alignment
◆ Nozzles may be clogged by adhesive ◆ K. Bean, IEEE Transactions on Electron Devices, Vol. ED-25, No. 10, 1978, pp 1185-1195
◆ Xerox 1990 Hawkins et al., USP 4,899,181 Glass capillaries Fine glass capillaries are drawn from glass tubing. This method has been used for macing individual nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. ◆ No expansive equipment required ◆ Simple to make single nozzles ◆ Very small nozzle sizes are difficult to form
◆ Not suited for mass production ◆ 1970 Zoltan USP 3,683,212 Monolithic, surface micro-machined using VLSI lithographic processes The nozzle plate is deposited as a layer using standard VLSI deposition techniques. Nozzles are etched in the nozzle plate using VLSI lithograph and etching. ◆ High accuracy (<1 µm)
◆ Monolithic
◆ Low cost
◆ Existing processes can be used ◆ Requires sacrificial layer under the nozzle plate to form the nozzle chamber
◆ Surface may be fragile to the touch ◆ Silverbrook, EP 0771 658 A2 and related patent applications
◆ IJ01, IJ02, IJ04, IJ11
◆ IJ12, IJ17, IJ18, IJ20
◆ IJ22, IJ24, IJ27, IJ28
◆ IJ29, IJ30, IJ31, IJ32
◆ IJ33, IJ34, IJ36, IJ37
◆ IJ38, IJ39, IJ40, IJ4
◆ IJ42, IJ43, IJ44 Monolithic, etched through substrate The nozzle plate is a buried etch stop in the wafer. Nozzle chambers are etched in the front of the wafer, and the wafer is thinned from the back side. Nozzles are then etched in the etch stop layer. ◆ High accuracy (<1 µm)
◆ Monolithic
◆ Low cost
◆ No differential expansion ◆ Requires long etch times
◆ Requires a support wafer ◆ IJ03, IJ05, IJ06, IJ07
◆ IJ08, IJ09, IJ10, IJ13
◆ IJ14, IJ15, IJ16, IJ19
◆ IJ21, IJ23, IJ25, IJ26 No nozzle plate Various methods have been tried to eliminate the nozzles entirely, to prevent nozzle clogging. These include thermal bubble mechanisms and acoustic lens mechanisms ◆ No nozzles to become clogged ◆ Difficult to control drop position accurately
◆ Crosstalk problems ◆ Ricoh 1995 Seklya et al USP 5,412,413
◆ 1993 Hadimioglu et al EUP 550,192
◆ 1993 Elrod et al EUP 572,220 Trough Each drop ejector has a trough through which a paddle moves. There is no nozzle plate. ◆ Reduced manufacturing complexity
◆ Monolithic ◆ Drop firing direction is sensitive to wicking. ◆ IJ35 Nozzle slit instead of individual nozzles The elimination of nozzle holes and replacement by a slit encompassing many actuator positions reduces nozzle clogging, but increases crosstalk due to ink surface waves ◆ No nozzles to become clogged ◆ Difficult to control drop position accurately
◆ Crosstalk problems ◆ 1989 Saito et al USP 4,799,068

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

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

A large number of new forms of ink jet printers have been developed to facilitate alternative ink jet technologies for the image processing and data distribution system. Various combinations of ink jet devices can be included in printer devices incorporated as part of the present invention.

Further, the present application may utilize advanced semiconductor fabrication techniques in the construction of large arrays of ink jet printers.

Further, the present application may utilize an ink delivery system to the ink jet head.

Further, the present application may utilize advanced semiconductor microelectromechanical techniques in the construction of large arrays of ink jet printers.

Further, the present application may include the utilization of a disposable camera system.

Further, the present application may include the utilization of a data distribution system.

Further, the present application may include the utilization of camera and data processing techniques such as an Artcam type device.

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 embodiment without departing from the scope of the invention as broadly described. The present embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive.