AU2005329726B2

AU2005329726B2 - Inkjet printhead having isolated nozzles

Info

Publication number: AU2005329726B2
Application number: AU2005329726A
Authority: AU
Inventors: Gregory John Mcavoy; Kia Silverbrook
Original assignee: Memjet Technology Ltd
Current assignee: Memjet Technology Ltd
Priority date: 2005-03-21
Filing date: 2005-03-21
Publication date: 2009-05-07
Anticipated expiration: 2025-03-21
Also published as: JP4473314B2; CA2592267C; WO2006099652A1; EP1861256A1; KR100973614B1; KR20070110449A; JP2008529848A; EP1861256A4; CA2592267A1; AU2005329726A1

Description

WO 2006/099652 PCT/AU2005/000392 1 INKJET PRINTHEAD HAVING ISOLATED NOZZLES CROSS REFERENCES TO RELATED APPLICATIONS The following patents or patent applications filed by the applicant or assignee of the 5 present invention are hereby incorporated by cross-reference. 6795215 10/884881 PECO1NP 09/575109 10/296535 09/575110 6805419 09/607985 6398332 6394573 6622923 6747760 10/189459 10/943941 10/949294 10/727181 10/727162 10/727163 10/727245 10/727204 10/727233 10/727280 10/727157 10/727178 10/727210 10/727257 10/727238 10/727251 10/727159 10/727180 10/727179 10/727192 10/727274 10/727164 10/727161 10/727198 10/727158 10/754536 10/754938 10/727227 10/727160 10/934720 10/854521 10/854522 10/854488 10/854487 10/854503 10/854504 10/854509 10/854510 10/854496 10/854497 10/854495 10/854498 10/854511 10/854512 10/854525 10/854526 10/854516 10/854508 10/854507 10/854515 10/854506 10/854505 10/854493 10/854494 10/85489 10/854490 10/854492 10/854491 10/854528 10/854523 10/854527 10/854524 10/854520 10/854514 10/854519 PLT036US 10/854499 10/854501 10/854500 10/854502 10/854518 10/854517 PLTO43US 10/728804 10/728952 10/728806 10/728834 10/729790 10/728884 10/728970 10/728784 10/728783 10/728925 10/728842 10/728803 10/728780 10/728779 10/773189 10/773204 10/773198 10/773199 10/773190 10/773201 10/773191 10/773183 10/773195 10/773196 10/773186 10/773200 10/773185 10/773192 10/773197 10/773203 10/773187 10/773202 10/773188 10/773194 10/773193 10/773184 10/760272 10/760273 10/760187 10/760182 10/760188 10/760218 10/760217 10/760216 10/760233 10/760246 10/760212 10/760243 10/760201 10/760185 10/760253 10/760255 10/760209 10/760208 10/760194 10/760238 10/760234 10/760235 10/760183 10/760189 10/760262 10/760232 10/760231 10/760200 10/760190 10/760191 10/760227 10/760207 10/760181 6746105 6623101 6406129 6505916 6457809 6550895 6457812 6428133 IJ52NP 10/407212 10/407207 10/683064 10/683041 10/882774 10/884889 10/922890 JUM008US 10/922885 10/922889 10/922884 10/922879 10/922887 10/922888 10/922874 10/922873 10/922871 10/922880 10/922881 10/922882 10/922883 10/922878 JUM023US 10/922876 10/922886 10/922877 10/815625 10/815624 10/815628 10/913375 10/913373 10/913374 10/913372 10/913377 10/913378 10/913380 10/913379 10/913376 10/913381 10/986402 09/575187 6727996 6591884 6439706 6760119 09/575198 09/722148 09/722146 09/721861 6290349 6428155 6785016 09/608920 09/721892 09/722171 09/721858 09/722142 10/171987 10/202021 10/291724 10/291512 10/291554 10/659027 10/659026 10/831242 10/884885 10/884883 10/901154 WO 2006/099652 PCT/AU2005/000392 2 10/932044 10/962412 10/962510 10/962552 10/965733 10/965933 10/974742 10/986375 10/659027 09/693301 09/575197 09/575195 09/575159 09/575132 09/575123 09/575148 09/575130 09/575165 6813039 09/575118 09/575131 09/575116 6816274 09/575139 09/575186 6681045 6728000 09/575145 09/575192 09/575181 09/575193 09/575183 6789194 09/575150 6789191 .6549935 09/575174 09/575163 6737591 09/575154 09/575129 09/575124 09/575188 09/575189 09/575170 09/575171 09/575161 6644642 6502614 6622999 6669385 11/003786 11/003354 CAA003US 11/003418 11/003334 CAA006US 11/003404 11/003419 11/003700 CAA010US CAA011US CAA012US 11/003337 CAA014US 11/003420 CAA016US CAA017US 11/003463 CAC001US 11/003683 CAE001US 11/003702 11/003684 CAF003US CAF004US 10/760254 10/760210 10/760202 10/760197 10/760198 10/760249 10/760263 10/760196 10/760247 10/760223 10/760264 10/760244 10/760245 10/760222 10/760248 10/760236 10/760192 10/760203 10/760204 10/760205 10/760206 10/760267 10/760270 10/760259 10/760271 10/760275 10/760274 10/760268 10/760184 10/760195 10/760186 10/760261 10/760258 RRB001US RRB002US RRB003US RRB004US RRB005US RRB006US RRB007US RRB008US RRB009US RRB010US RRB011US RRB012US RRB013US RRB014US RRB015US RRB016US RRB017US RRB018US RRB019US RRB020US RRB021US RRB022US RRB023US RRB024US RRB025US RRB026US RRB027US RRB030US RRB031US RRB032US RRB033US RRC001US RRC002US RRC003US RRC004US RRC005US RRC006US RRC007US RRC008US RRC009US RRC010US RRC011US RRC012US RRC013US RRC014US RRC015US RRC016US RRC017US RRC018US RRC019US RRC020US RRC021US 6750901 6476863 6788336 6322181 Some applications have been listed by docket numbers. These will be replaced when application numbers are known. 5 FIELD OF THE INVENTION The present invention relates to the field of inkjet printers and, discloses an inkjet printing system using printheads manufactured with microelectro-mechanical systems (MEMS) techniques. -10 BACKGROUND OF THE INVENTION Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print WO 2006/099652 PCT/AU2005/000392 3 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 5 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. 10 Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988). Ink Jet printers themselves come in many different types. The utilization of a 15 continuous stream of ink in ink jet 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 20 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) Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which 25 discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US Patent No. 4459601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in US 4584590 which discloses a shear mode type of piezoelectric transducer element. Recently, thermal ink jet printing has become an extremely popular form of ink jet 30 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 that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby WO 2006/099652 PCT/AU2005/000392 4 causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. As can be seen from the foregoing, many different types of printing technologies are 5 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. 10 A problem with inkjet printheads, and especially inkjet printheads having a high nozzle density, is that ink can flood across the printhead surface contaminating adjacent nozzles. This is undesirable because it results in reduced print quality. Moreover, cross contamination of ink across the printhead surface can potentially result in electrolysis and accelerated corrosion of nozzle actuators. 15 Previous attempts to minimize ink flooding across the printhead surface typically involve coating the printhead with a hydrophobic material. However, hydrophobic coatings have only had limited success in minimizing the extent of flooding. A further problem with inkjet printheads, especially inkjet printheads having senstitive MEMS nozzles formed on an ink ejection surface of the printhead, is that the 20 nozzle structures can become damaged by cleaning the printhead surface. Typically, printheads are wiped regularly to remove particles of paper dust or paper fibers, which build up on the ink ejection surface. When a wiping mechanism comes into contact with nozzle structures on the printhead surface, there is an obvious risk of damaging the nozzles. It would be desirable to provide a printhead, which minimizes cross-contamination 25 by ink flooding between adjacent nozzles. It would be further desirable to provide a printhead, which allows regular cleaning of the printhead surface by a wiping mechanism without risk of damaging nozzle structures on the printhead. SUMMARY OF THE INVENTION 30 In a first aspect, there is provided a printhead comprising: WO 2006/099652 PCT/AU2005/000392 5 a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being 5 configured to isolate each nozzle from at least one adjacent nozzle. In a second aspect, there is provided a method of operating a printhead, whilst minimizing cross-contamination of ink between adjacent nozzles, the method comprising the steps of: 10 (a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzles having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being 15 configured to isolate each nozzle from at least one adjacent nozzle; and (b) printing onto a print medium using said printhead. In a third aspect, there is provided a method of fabricating a printhead having isolated nozzles, the method comprising the steps of: 20 (a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; (b) depositing a layer of photoresist over the ink ejection surface; (c) defining recesses in the photoresist, each recess revealing a portion of the ink 25 ejection surface surrounding a respective nozzle aperture; (d) depositing a roof material over the photoresist and into the recesses; (e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and 30 (f) removing the photoresist. Optionally, the formations have a hydrophobic surface. Inkjet inks are typically aqueous-based inks and hydrophobic formations will repel any flooded ink. Hence, WO 2006/099652 PCT/AU2005/000392 6 hydrophobic formations minimize as far as possible any cross-contamination of ink by acting as a physical barrier and by intermolecular repulsive forces. Moreover, hydrophobic formations promote ingestion of any flooded ink back into respective nozzle chambers and ink supply channels. Since nozzle chambers are typically hydrophilic, ink will tend to be 5 drawn back into the nozzle and away from a surrounding hydrophobic formation. Optionally, the formations are arranged in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface. Hence, each nozzle is isolated from its adjacent nozzles by a nozzle enclosure. 10 Optionally, each nozzle enclosure further comprises a roof spaced apart from the respective nozzle, the roof having a roof opening aligned with a respective nozzle opening for allowing ejected ink droplets to pass therethrough onto the print medium. Hence, each nozzle enclosure may typically take the form of a cap, which covers or encapsulates an individual nozzle on the ink ejection surface. The roof not only provides additional 15 containment of any flooded ink, it also provides further protection of each nozzle from, for example, the potentially damaging effects of paper dust, paper fibers or wiping. Typically, the sidewalls extend from a perimeter region of each roof to the ink ejection surface. Sidewalls of adjacent nozzle enclosures are usually spaced apart across the ink ejection surface. 20 Optionally, the printhead is an inkjet printhead, such as a pagewidth inkjet printhead. Optionally, the printhead has a nozzle density, which is sufficient to print at up to 1600 dpi. The present invention is particularly beneficial for printheads having a high nozzle density, because high density printheads are especially prone to flooding between adjacent nozzles. 25 BRIEF DESCRIPTION OF THE DRAWINGS Notwithstanding any other forms that may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 30 Fig. 1 is a schematic cross-sectional view through an ink chamber of a unit cell of a printhead according to an embodiment using a bubble forming heater element; WO 2006/099652 PCT/AU2005/000392 7 Fig. 2 is a schematic cross-sectional view through the ink chamber Fig. 1, at another stage of operation; Fig. 3 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet 5 another stage of operation; Fig. 4 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet a further stage of operation; and 10 Fig. 5 is a diagrammatic cross-sectional view through a unit cell of a printhead in accordance with an embodiment of the invention showing the collapse of a vapor bubble. Fig. 6 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead. 15 Figs. 7 to 20 are schematic perspective views of the unit cell shown in Fig. 6, at various successive stages in the fabrication process of the printhead. DESCRIPTION OF OPTIONAL EMBODIMENTS 20 Bubble Forming Heater Element Actuator With reference to Figures 1 to 4, the unit cell 1 of one of the Applicant's printheads is shown. The unit cell 1 comprises a nozzle plate 2 with nozzles 3 therein, the nozzles having nozzle rims 4, and apertures 5 extending through the nozzle plate. The nozzle plate 25 2 is plasma etched from a silicon nitride structure which is deposited, by way of chemical vapor deposition (CVD), over a sacrificial material which is subsequently etched. The printhead also includes, with respect to each nozzle 3, side walls 6 on which the nozzle plate is supported, a chamber 7 defined by the walls and the nozzle plate 2, a multi 30 layer substrate 8 and an inlet passage 9 extending through the multi-layer substrate to the far side (not shown) of the substrate. A looped, elongate heater element 10 is suspended within the chamber 7, so that the element is in the form of a suspended beam. The WO 2006/099652 PCT/AU2005/000392 8 printhead as shown is a microelectromechanical system (MEMS) structure, which is formed by a lithographic process which is described in more detail below. When the printhead is in use, ink 11 from a reservoir (not shown) enters the 5 chamber 7 via the inlet passage 9, so that the chamber fills to the level as shown in Figure 1. Thereafter, the heater element 10 is heated for somewhat less than 1 microsecond, so that the heating is in the form of a thermal pulse. It will be appreciated that the heater element 10 is in thermal contact with the ink 11 in the chamber 7 so that when the element is heated, this causes the generation of vapor bubbles 12 in the ink. Accordingly, the ink 11 10 constitutes a bubble forming liquid. Figure 1 shows the formation of a bubble 12 approximately 1 microsecond after generation of the thermal pulse, that is, when the bubble has just nucleated on the heater elements 10. It will be appreciated that, as the heat is applied in the form of a pulse, all the energy necessary to generate the bubble 12 is to be supplied within that short time. 15 When the element 10 is heated as described above, the bubble 12 forms along the length of the element, this bubble appearing, in the cross-sectional view of Figure 1, as four bubble portions, one for each of the element portions shown in cross section. 20 The bubble 12, once generated, causes an increase in pressure within the chamber 7, which in turn causes the ejection of a drop 16 of the ink 11 through the nozzle 3. The rim 4 assists in directing the drop 16 as it is ejected, so as to minimize the chance of drop misdirection. 25 The reason that there is only one nozzle 3 and chamber 7 per inlet passage 9 is so that the pressure wave generated within the chamber, on heating of the element 10 and forming of a bubble 12, does not affect adjacent chambers and their corresponding nozzles. The pressure wave generated within the chamber creates significant stresses in the chamber wall. Forming the chamber from an amorphous ceramic such as silicon nitride, silicon 30 dioxide (glass) or silicon oxynitride, gives the chamber walls high strength while avoiding the use of material with a crystal structure. Crystalline defects can act as stress concentration points and therefore potential areas of weakness and ultimately failure.

WO 2006/099652 PCT/AU2005/000392 9 Figures 2 and 3 show the unit cell 1 at two successive later stages of operation of the printhead. It can be seen that the bubble 12 generates further, and hence grows, with the resultant advancement of ink 11 through the nozzle 3. The shape of the bubble 12 as it grows, as shown in Figure 3, is determined by a combination of the inertial dynamics and 5 the surface tension of the ink 11. The surface tension tends to minimize the surface area of the bubble 12 so that, by the time a certain amount of liquid has evaporated, the bubble is essentially disk-shaped. The increase in pressure within the chamber 7 not only pushes ink 11 out through 10 the nozzle 3, but also pushes some ink back through the inlet passage 9. However, the inlet passage 9 is approximately 200 to 300 microns in length, and is only approximately 16 microns in diameter. Hence there is a substantial viscous drag. As a result, the predominant effect of the pressure rise in the chamber 7 is to force ink out through the nozzle 3 as an ejected drop 16, rather than back through the inlet passage 9. 15 Turning now to Figure 4, the printhead is shown at a still further successive stage of operation, in which the ink drop 16 that is being ejected is shown during its "necking phase" before the drop breaks off. At this stage, the bubble 12 has already reached its maximum size and has then begun to collapse towards the point of collapse 17, as reflected 20 in more detail in Figure 21. The collapsing of the bubble 12 towards the point of collapse 17 causes some ink 11 to be drawn from within the nozzle 3 (from the sides 18 of the drop), and some to be drawn from the inlet passage 9, towards the point of collapse. Most of the ink 11 drawn in this 25 manner is drawn from the nozzle 3, forming an annular neck 19 at the base of the drop 16 prior to its breaking off. The drop 16 requires a certain amount of momentum to overcome surface tension forces, in order to break off. As ink 11 is drawn from the nozzle 3 by the collapse of the 30 bubble 12, the diameter of the neck 19 reduces thereby reducing the amount of total surface tension holding the drop, so that the momentum of the drop as it is ejected out of the nozzle is sufficient to allow the drop to break off.

WO 2006/099652 PCT/AU2005/000392 10 When the drop 16 breaks off, cavitation forces are caused as reflected by the arrows 20, as the bubble 12 collapses to the point of collapse 17. It will be noted that there are no solid surfaces in the vicinity of the point of collapse 17 on which the cavitation can have an effect. 5 Advantages of Nozzle Enclosures Referring to Figure 6, an embodiment of the unit cell 1 according to the invention is shown. The aperture 5 is surrounded by a nozzle enclosure 60, which isolates adjacent apertures on the printhead. The nozzle enclosure 60 has a roof 61 and sidewalls 62, which 10 extend from the roof to the nozzle plate 2 and form a seal therewith. An opening 63 is defined in the roof 61, which allows ink droplets (not shown) to pass through the nozzle enclosure and onto a print medium (not shown). The nozzle enclosure 60 minimize cross-contamination between adjacent apertures 5 by containing any flooded ink in the immediate vicinity of each nozzle. Flooding of ink 15 from each nozzle may be caused by a variety of reasons, such as nozzle misfires or pressure fluctuations in ink supply channels. The nozzle enclosure may be formed from or coated with a hydrophobic material during the fabrication process, which further minimizes the risk of cross-contamination. A further advantage of the printhead according to the invention is that it allows the 20 nozzle plate 2 of the printhead to be wiped without risk of damaging the sensitive nozzle structures. Typically, inkjet printheads are cleaned by a wiping mechanism as part of a warm-up cycle. The nozzle enclosures 60 provide a protective barrier between the nozzles and the wiping mechanism (not shown). 25 Fabrication Process In the interests of brevity, the fabrication stages have been shown for the unit cell of Figure 6 only (see Figures 7 to 20). It will be appreciated that the other unit cells will use the same fabrication stages with different masking. 30 Referring to Figure 7, there is shown the starting point for fabrication of the thermal inkjet nozzle shown in Figure 13. CMOS processing of a silicon wafer provides a silicon substrate 21 having drive circuitry 22, and an interlayer dielectric ("interconnect") 23. The interconnect 23 comprises four metal layers, which together form a seal ring for the inlet WO 2006/099652 PCT/AU2005/000392 11 passage 9 to be etched through the interconnect. The top metal layer 26, which forms an upper portion of the seal ring, can be seen in Figure 7. The metal seal ring prevents ink moisture from seeping into the interconnect 23 when the inlet passage 9 is filled with ink. 5 A passivation layer 24 is deposited onto the top metal layer 26 by plasma-enhanced chemical vapour deposition (PECVD). After deposition of the passivation layer 24, it is etched to define a circular recess, which forms parts of the inlet passage 9. At the same as etching the recess, a plurality of vias 50 are also etched, which allow electrical connection through the passivation layer 24 to the top metal layer 26. The etch pattern is defined by a 10 layer of patterned photoresist (not shown), which is removed by 02 ashing after the etch. Referring to Figure 8, in the next fabrication sequence, a layer of photoresist is spun onto the passivation later 24. The photoresist is exposed and developed to define a circular opening. With the patterned photoresist 51 in place, the dielectric interconnect 23 is etched 15 as far as the silicon substrate 21 using a suitable oxide-etching gas chemistry (e.g. 0 2

/C

4

F

8 ). Etching through the silicon substrate is continued down to about 20 microns to define a front ink hole 52, using a suitable silicon-etching gas chemistry (e.g. 'Bosch etch'). The same photoresist mask 51 can be used for both etching steps. Figure 9 shows the unit cell after etching the front ink hole 52 and removal of the photoresist 51. 20 Referring to Figure 10, in the next stage of fabrication, the front ink hole 52 is plugged with photoresist to provide a front plug 53. At the same time, a layer of photoresist is deposited over the passivation layer 24. This layer of photoresist is exposed and developed to define a first sacrificial scaffold 54 over the front plug 53, and scaffolding 25 tracks 35 around the perimeter of the unit cell. The first sacrificial scaffold 54 is used for subsequent deposition of heater material 38 thereon and is therefore formed with a planar upper surface to avoid any buckling in the heater element (see heater element 10 in Figure 10). The first sacrificial scaffold 54 is UV cured and hardbaked to prevent reflow of the photoresist during subsequent high-temperature deposition onto its upper surface. 30 Importantly, the first sacrificial scaffold 54 has sloped or angled side faces 55. These angled side faces 55 are formed by adjusting the focusing in the exposure tool (e.g.

WO 2006/099652 PCT/AU2005/000392 12 stepper) when exposing the photoresist. The sloped side faces 55 advantageously allow heater material 38 to be deposited substantially evenly over the first sacrificial scaffold 54. Referring to Figure 11, the next stage of fabrication deposits the heater material 38 5 over the first sacrificial scaffold 54, the passivation layer 24 and the perimeter scaffolding tracks 35. The heater material 38 is typically a monolayer of TiAlN. However, the heater material 38 may alternatively comprise TiAlN sandwiched between upper and lower passivating materials, such as tantalum or tantalum nitride. Passivating layers on the heater element 10 minimize corrosion of the and improve heater longevity. 10 Referring to Figure 12, the heater material 38 is subsequently etched down to the first sacrificial scaffold 54 to define the heater element 10. At the same time, contact electrodes 15 are defined on either side of the heater element 10. The electrodes 15 are in contact with the top metal layer 26 and so provide electrical connection between the CMOS 15 and the heater element 10. The sloped side faces of the first sacrificial scaffold 54 ensure good electrical connection between the heater element 10 and the electrodes 15, since the heater material is deposited with sufficient thickness around the scaffold 54. Any thin areas of heater material (due to insufficient side face deposition) would increase resistivity and affect heater performance. 20 Adjacent unit cells are electrically insulated from each other by virtue of grooves etched around the perimeter of each unit cell. The grooves are etched at the same time as defining the heater element 10. 25 Referring to Figure 13, in the subsequent step a second sacrificial scaffold 39 of photoresist is deposited over the heater material. The second sacrificial scaffold 39 is exposed and developed to define sidewalls for the cylindrical nozzle chamber and perimeter sidewalls for each unit cell. The second sacrificial scaffold 39 is also UV cured and hardbaked to prevent any reflow of the photoresist during subsequent high-temperature 30 deposition of the silicon nitride roof material. Referring to Figure 14, silicon nitride is deposited onto the second sacrificial scaffold 39 by plasma enhanced chemical vapour deposition. The silicon nitride forms a WO 2006/099652 PCT/AU2005/000392 13 roof 44 over each unit cell, which is the nozzle plate 2 for a row of nozzles. Chamber sidewalls 6 and unit cell sidewalls 56 are also formed by deposition of silicon nitride. Referring to Figure 15, the nozzle rim 4 is etched partially through the roof 44, by 5 placing a suitably patterned photoresist mask over the roof, etching for a controlled period of time and removing the photoresist by ashing. Referring to Figure 16, the nozzle aperture 5 is etched through the roof 24 down to the second sacrificial scaffold 39. Again, the etch is performed by placing a suitably 10 patterned photoresist mask over the roof, etching down to the scaffold 39 and removing the photoresist mask. Referring to Figure 17, in the next stage a third sacrificial scaffold 64 is deposited over the roof 44. The third sacrificial scaffold 64 is exposed and developed to define 15 sidewalls for the cylindrical nozzle enclosure over each aperture 5. The third sacrificial scaffold 64 is also UV cured and hardbaked to prevent any reflow of the photoresist during subsequent high-temperature deposition of the nozzle enclosure material. Referring to Figure 18, silicon nitride is deposited onto the third sacrificial scaffold 20 64 by plasma enhanced chemical vapour deposition. The silicon nitride forms an enclosure roof 61 over each aperture 5. Enclosure sidewalls 62 are also formed by deposition of silicon nitride. Whilst silicon nitride is deposited in the embodiment shown, the enclosure roof 61 may equally be formed from silicon oxide, silicon oxynitride etc. Optionally, a layer of hydrophobic material (e.g. fluoropolymer) is deposited onto the enclosure roof 61 25 after deposition. This extra deposition step may be performed at any stage after deposition (e.g. after etching or after ashing). Referring to Figure 19, the nozzle enclosure 60 is formed by etching through the enclosure roof layer 61. The enclosure opening 63 is defined by this etch. In addition, the 30 enclosure roof material which is located outside the enclosure sidewalls 62 is removed. The etch pattern is defined by standard photoresist masking.

WO 2006/099652 PCT/AU2005/000392 14 With the nozzle structure, including nozzle enclosure 60, now fully formed on a frontside of the silicon substrate 21, an ink supply channel 32 is etched from the backside of the substrate 21, which meets with the front plug 53. 5 Referring to Figure 20, after formation of the ink supply channel 32, the first, second and sacrificial scaffolds of photoresist, together with the front plug 53 are ashed off using an 02 plasma. Accordingly, fluid connection is made from the ink supply channel 32 through to the nozzle aperture 5 and the nozzle enclosure opening 63. 10 It should be noted that a portion of photoresist, on either side of the nozzle chamber sidewalls 6, remains encapsulated by the roof 44, the unit cell sidewalls 56 and the chamber sidewalls 6. This portion of photoresist is sealed from the 02 ashing plasma and, therefore, remains intact after fabrication of the printhead. This encapsulated photoresist advantageously provides additional robustness for the printhead by supporting the nozzle 15 plate 2. Hence, the printhead has a robust nozzle plate spanning continuously over rows of nozzles, and being supported by solid blocks of hardened photoresist, in addition to support walls. Other Embodiments 20 The invention has been described above with reference to printheads using bubble forming heater elements. However, it is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable 25 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, 30 billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

WO 2006/099652 PCT/AU2005/000392 15 It will be appreciated by ordinary workers in this field that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not 5 restrictive. Ink Jet Technologies The embodiments of the invention use an ink jet printer type device. Of course many 10 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 15 means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. In conventional thermal inkjet printheads, this leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out. 20 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 25 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 30 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) WO 2006/099652 PCT/AU2005/000392 16 photographic quality output low manufacturing cost small size (pagewidth times minimum cross section) high speed (<2 seconds per page). 5 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 10 out in the table under the heading Cross References to Related Applications. The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems. 15 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 20 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 25 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 30 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.

WO 2006/099652 PCT/AU2005/000392 17 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) 5 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) 10 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 15 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. 20 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. 25 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. 30 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 WO 2006/099652 PCT/AU2005/000392 18 printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc. The information associated with the aforementioned 11 dimensional matrix are set 5 out in the following tables.

WO 2006/099652 PCT/AU2005/000392 19 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal An electrothermal Large force High power Canon Bubblejet bubble heater heats the ink to generated Ink carrier 1979 Endo et al GB above boiling point, Simple limited to water patent 2,007,162 transferring significant construction Low efficiency Xerox heater-in heat to the aqueous No moving parts High pit 1990 Hawkins et ink. A bubble Fast operation temperatures al USP 4,899,181 nucleates and quickly Small chip area required Hewlett-Packard forms, expelling the required for actuator High mechanical TIJ 1982 Vaught et ink. stress al USP 4,490,728 The efficiency of the * Unusual process is low, with materials required typically less than Large drive 0.05% of the electrical transistors energy being * Cavitation causes transformed into actuator failure kinetic energy of the Kogation reduces drop. bubble formation Large print heads are difficult to fabricate Piezo- A piezoelectric crystal Low power Very large area Kyser et al USP electric such as lead consumption required for actuator 3,946,398 lanthanum zirconate Many ink types Difficult to Zoltan USP (PZT) is electrically can be used integrate with 3,683,212 activated, and either Fast operation electronics 1973 Stemme expands, shears, or * High efficiency * High voltage USP 3,747,120 bends to apply drive transistors Epson Stylus pressure to the ink, required Tektronix ejecting drops. Full pagewidth J04 print heads impractical due to actuator size Requires electrical poling in high field strengths During manufacture Electro- An electric field is Low power mLow maximum Seiko Epson, strictive used to activate consumption strain (approx. Usui et all JP electrostriction in +Many ink types 0.01%) 253401/96 relaxor materials such can be used *aLarge area IJ04 as lead lanthanum. * Low thermal required for actuator zirconate titanate expansion due to low strain (PLZT) or lead * Electric field * Response speed magnesium niobate strength required is marginal (- 10 (PMN). (approx. 3.5 Vblm) s) can be generated High voltage without difficulty drive transistors * Does not require required electrical poling Full pagewidth print heads impractical due to activateractuator size WO 2006/099652 PCT/AU2005/000392 20 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Ferro- An electric field is Low power Difficult to IJ04 electric used to induce a phase consumption integrate with transition between the Many ink types electronics antiferroelectric (AFE) can be used Unusual and ferroelectric (FE) Fast operation materials such as phase. Perovskite (< Is) PLZSnT are materials such as tin Relatively high required modified lead longitudinal strain Actuators require lanthanum zirconate High efficiency a large area titanate (PLZSnT) Electric field exhibit large strains of strength of around 3 up to 1% associated V/jim can be readily with the AFE to FE provided phase transition. Electro- Conductive plates are * Low power * Difficult to * 1J02, IJ04 static plates separated by a consumption operate electrostatic compressible or fluid * Many ink types devices in an dielectric (usually air). can be used aqueous Upon application of a Fast operation environment voltage, the plates * The electrostatic attract each other and actuator will displace ink, causing normally need to be drop ejection. The separated from the conductive plates may ink be in a comb or * Very large area honeycomb structure, required to achieve or stacked to increase high forces the surface area and High voltage therefore the force, drive transistors may be required *Full pagewidth print heads are not competitive due to actuator size Electro- A strong electric field Low current High voltage 1989 Saito et al, static pull is applied to the ink, consumption required USP 4,799,068 on ink whereupon Low temperature May be damaged 1989 Miura et al, electrostatic attraction by sparks due to air USP 4,810,954 accelerates the ink breakdown Tone-jet towards the print Required field medium. strength increases as the drop size decreases *High voltage drive transistors required orElectrostatic field Sdattractsdust WO 2006/099652 PCT/AU2005/000392 21 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Permanent An electromagnet + Low power Complex 1J07, IJ10 magnet directly attracts a consumption fabrication electro- permanent magnet, + Many ink types Permanent magnetic displacing ink and can be used magnetic material causing drop ejection. + Fast operation such as Neodymium Rare earth magnets + High efficiency Iron Boron (NdFeB) with a field strength + Easy extension required. around 1 Tesla can be from single nozzles High local used. Examples are: to pagewidth print currents required Samarium Cobalt heads Copper (SaCo) and magnetic metalization should materials in the be used for long neodymium iron boron electromigration family (NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) * Pigmented inks are usually infeasible faOperating temperature limited to the Curie temperature (around 540 K) Soft A solenoid induced a * Low power * Complex I IJ~, IJOS, IJ08, magnetic magnetic field in a soft consumption fabrication e1n, tJ12, 1J14, core electro- magnetic core or yoke * Many ink types * Materials not IJiS, IJ17 magnetic fabricated from a can be used usually present in a ferrous material such * Fast operation CMOS fab such as as electroplated iron * High efficiency NiFe, CoNiFe, or alloys such as CoNiFe * Easy extension CoFe are required [1], CoFe, or NiFe from single nozzles High local alloys. Typically, the to pagewidth print currents required soft magnetic material heads Copper is in two parts, which *metalization should are normally held be used for long apart by a spring. electromigration When the solenoid is lifetime and low actuated, the two parts resistivity attract, displacing the Electroplating is required High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) WO 2006/099652 PCT/AU2005/000392 22 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Lorenz The Lorenz force + Low power Force acts as a * 106, 13111, 1313, force acting on a current consumption twisting motion IJ16 carrying wire in a + Many ink types Typically, only a magnetic field is can be used quarter of the utilized. + Fast operation solenoid length This allows the + High efficiency provides force in a magnetic field to be + Easy extension useful direction supplied externally to from single nozzles High local the print head, for to pagewidth print currents required example with rare heads Copper earth permanent metalization should magnets. be used for long Only the current electromigration carrying wire need be lifetime and low fabricated on the print- resistivity head, simplifying Pigmented inks materials are usually Requirements. infeasible Magneto- The actuator uses the Many ink types Force acts as a + Fischenbeck, striction giant magnetostrictive can be used twisting motion USP 4,032,929 effect of materials Fast operation Unusual t '25 such as Terfenol-D (an * Easy extension materials such as alloy of terbium, from single nozzles Tefenol-D are dysprosium and iron to pagewidth print required developed at the Naval heads High local Ordnance Laboratory, * High force is currents required hence Ter-Fe-NOL). available Copper For best efficiency, the metalization should actuator should be pre- be used for long stressed to approx. 8 electromigration MIPa. lifetime and low resistivity + Pre-stressing may be requiredally Surface Ink under positive * Low power * Requires * Silverbrook, EP tension pressure is held in a consumption supplementary force 0771658 A2 and reduction nozzle by surface Simple to effect drop related patent tension. The surface construction separation applications tension of the ink is * No unusual * Requires special reduced below the materials required in ink surfactants bubble threshold, fabrication * Speed may be causing the ink to * High efficiency limited by surfactant egress from the Easy extension properties nozzle. from single nozzles henceTer-Fe- ) heads WO 2006/099652 PCT/AU2005/000392 23 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Viscosity The ink viscosity is + Simple Requires Silverbrook, EP reduction locally reduced to construction supplementary force 0771658 A2 and select which drops are * No unusual to effect drop related patent to be ejected. A materials required in separation applications viscosity reduction can fabrication Requires special be achieved Easy extension ink viscosity electrothermally with from single nozzles properties most inks, but special to pagewidth print High speed is inks can be engineered heads difficult to achieve for a 100:1 viscosity * Requires reduction. oscillating ink pressure * A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave is * Can operate * Complex drive * 1993 Hadimioglu generated and without a nozzle circuitry et al, EUP 550,192 focussed upon the plate * Complex * 1993 Elrod et al, drop ejection region. fabrication EUP 572,220 +Low efficiency *Poor control of drop position f sPoor control of drop volume Thermo- An actuator which + Low power Efficient aqueous U03, U09, IJ 7, elastic bend relies upon differential consumption operation requires a 1118, 1119, 1120, actuator thermal expansion + Many ink types thermal insulator on 1121, 1122, 1123, upon Joule heating is can be used the hot side 1124, IJ27, 1128, used. + Simple planar Corrosion 1129, 1130, 1J31, fabrication prevention can be IJ32,I133,1J34, + Small chip area difficult 1135, IJ36, 1137, required for each Pigmented inks IJ38 ,J39, IJ40, actuator may be infeasible, IJ41 + Fast operation as pigment particles + High efficiency may jam the bend + CMOS actuator compatible voltages and currents + Standard MEMS processes can be used + Easy extension from single nozzles to pagewidth print __________ ________________ heads___________ __________ WO 2006/099652 PCT/AU2005/000392 24 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples High CTE A material with a very High force can Requires special * J09, IJ 7, IJ 8, thermo- high coefficient of be generated material (e.g. PTFE) IJ20, 1J2 1, 1J22, elastic thermal expansion Three methods of Requires a PTFE IJ23, 1J24, 1J27, actuator (CTE) such as PTFE deposition are deposition process, IJ28, 1J29, IJ30, polytetrafluoroethylen under development: which is not yet IJ3 1, IJ42, 1J43, e (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTE materials deposition (CVD), fabs are usually non- spin coating, and PTFE deposition conductive, a heater evaporation cannot be followed fabricated from a PTFE is a with high conductive material is candidate for low temperature (above incorporated. A 50 pm dielectric constant 350 'C) processing long PTFE bend insulation in ULSI Pigmented inks actuator with Very low power may be infeasible, polysilicon heater and consumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 pN can be used actuator force and 10 pm Simple planar deflection. Actuator fabrication motions include: Small chip area Bend required for each Push actuator Buckle Fast operation Rotate High efficiency * CMOs compatible voltages and currents TEasy extension from single nozzles to pagewidth print heads Conduct-ive A polymer with a high High force can Requires special J24 polymer coefficient of thermal be generated materials thermo- expansion (such as * Very low power development (High elastic PTFE) is doped with consumption GTE conductive actuator conducting substances dMany ink types polymer) to increase its can be used Requires a PTFE conductivity to about 3 Simple planar deposition process, orders of magnitude fabrication which is not yet below that of copper. Small chip area standard in ILSI The conducting required for each fabs polymer expands actuator PTFE deposition when resistively Fast operation cannot be followed heated. High efficiency with high Examples of CMOS temperature (above conducting dopants compatible voltages 350 *C) processing include: and currents Evaporation and Carbon nanotubes Easy extension CVD deposition Metal fibers from single nozzles techniques cannot Conductive polymers to pagewidth print be used such as doped heads Pigmented inks polythiophene may be infeasible, has pigment particles may jam the bend actuator WO 2006/099652 PCT/AU2005/000392 25 ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Shape A shape memory alloy * High force is Fatigue limits IJ26 memory such as TiNi (also available (stresses maximum number alloy known as Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy * Large strain is Low strain (1%) developed at the Naval available (more than is required to extend Ordnance Laboratory) 3%) fatigue resistance is thermally switched High corrosion Cycle rate between its weak resistance limited by heat martensitic state and Simple removal its high stiffness construction Requires unusual austenic state. The Easy extension materials (TiNi) shape of the actuator from single nozzles The latent heat of in its martensitic state to pagewidth print transformation must is deformed relative to heads be provided the austenic shape. Low voltage High current The shape change operation operation causes ejection of a Requires pre drop. stressing to distort the martensitic state Linear Linear magnetic * Linear Magnetic * Requires unusual * IJ 12 Magnetic actuators include the actuators can be semiconductor Actuator Linear Induction constructed with materials such as Actuator (LIA), Linear high thrust, long soft magnetic alloys Permanent Magnet travel, and high (e.g. CoNiFe) Synchronous Actuator efficiency using * Some varieties (LPMSA), Linear planar also require Reluctance semiconductor permanent magnetic Synchronous Actuator fabrication materials such as (LRSA), Linear techniques Neodymium iron Switched Reluctance * Long actuator boron (NdFeB) Actuator (LSRA), and travel is available * Requires the Linear Stepper * Medium force is complex multi Actuator (LSA). available phase drive circuitry + Low voltage High current operation operation [BASIC OPERATION MODE Description Advantages Disadvantages Examples WO 2006/099652 PCT/AU2005/000392 26 BASIc OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the simplest Simple operation Drop repetition Thermal inkjet directly mode of operation: the No external rate is usually Piezoelectric ink pushes ink actuator directly fields required limited to around 10 jet supplies sufficient Satellite drops klz. However, this UJ1, 1J02, 1J03, kinetic energy to expel can be avoided if is not fundamental 1104,1105, 106, the drop. The drop drop velocity is less to the method, but is 1107,IJ09,l111, must have a sufficient than 4 m/s related to the refill 1112, IJ14, 1116, velocity to overcome Can be efficient, method normally IJ20, 1122, 1123, the surface tension, depending upon the used 1124, IJ25, 1126, actuator used * All of the drop 1127, 1J28, 1129, kinetic energy must 1130, U131,11J32, be provided by the rq33, 34, J35, actuator IJ36, 1137, IJ38, +Satellite drops J39, 1J40, IJ41, usually form if drop 1142, 1143, IJ44 velocity is greater than 4.5 m/s Proximity The drops to be Very simple print Requires close Silverbrook, EP printed are selected by head fabrication can proximity between 0771 658 A2 and some manner (e.g. be used the print head and related patent thermally induced * The drop the print media or applications surface tension selection means transfer roller reduction of does not need to May require two pressurized ink). provide the energy print heads printing Selected drops are required to separate alternate rows of the separated from the ink the drop from the image in the nozzle by nozzle Monolithic color contact with the print print heads are medium or a transfer difficult roller. Electro- The drops to be * Very simple print * Requires very -Silverbrook, EP static pull printed are selected by head fabrication can high electrostatic 0771 658 A2 and on ink some manner (e.g. be used field related patent thermally induced * The drop * Electrostatic field applications surface tension selection means for small nozzle * Tone-let reduction of does not need to sizes is above air pressurized ink). provide the energy breakdown Selected drops are required to separate * Electrostatic field separated from the ink the drop from the may attract dust in the nozzle by a nozzle strong electric field.P Magnetic The drops to be * Very simple print * Requires * 'Silverbrook, EP pull on ink printed are selected by head fabrication can magnetic ink 0771 658 A2 and some manner (e.g. be used * Ink colors other related patent thermally induced * The drop than black are applications surface tension selection means difficult reduction of does not need to * Requires very pressurized ink), provide the energy high magnetic fields Selected drops are required to separate separated from the ink the drop from the in the nozzle by a nozzle strong magnetic field acting on the magnetic ______ ink. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ WO 2006/099652 PCT/AU2005/000392 27 BASIC OPERATION MODE Description Advantages Disadvantages Examples Shutter The actuator moves a High speed (>50 Moving parts are * J13, U17, IJ21 shutter to block ink kHz) operation can required flow to the nozzle. The be achieved due to Requires ink ink pressure is pulsed reduced refill time pressure modulator at a multiple of the Drop timing can Friction and wear drop ejection be very accurate must be considered frequency. The actuator Stiction is energy can be very possible low Shuttered The actuator moves a *+Actuators with Moving parts are U08, U15, U18, grill shutter to block ink small travel can be required IJ19 flow through a grill to used Requires ink the nozzle. The shutter * Actuators with pressure modulator movement need only small force can be Friction and wear be equal to the width used must be considered of the grill holes. +High speed (>50 Stiction is kHz) operation can possible be achieved Pulsed A pulsed magnetic * Extremely low * Requires an U J10 magnetic field attracts an 'ink energy operation is external pulsed pull on ink pusher' at the drop possible magnetic field pusher ejection frequency. An * No heat + Requires special actuator controls a dissipation materials for both catch, which prevents problems the actuator and the the ink pusher from ink pusher moving when a drop is * Complex not to be ejected. construction WO 2006/099652 PCT/AU2005/000392 28 AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator directly + Simplicity of Drop ejection Most ink jets, fires the ink drop, and construction energy must be including there is no external + Simplicity of supplied by piezoelectric and field or other operation individual nozzle thermal bubble. mechanism required. + Small physical actuator * ii,1302,1303, size UJ04, U305, 1307, D09, e11,jt12, r14, m20, s22, U323, UJ24, 1325, UJ26, U327,1328, UJ29, U330,1U31, 1332, 1333, 1334, UJ35, U336, U337, UJ38, U339, UJ40, 1341, 1342, 1343, IJ44 Oscillating The ink pressure * Oscillating ink * Requires external * Silverbrook, EP ink pressure oscillates, providing pressure can provide ink pressure 0771658 A2 and (including much of the drop a refill pulse, oscillator related patent acoustic ejection energy. The allowing higher tInk pressure applications stimul- actuator selects which operating speed phase and amplitude * 1U08, U313, U315, ation) drops are to be fired IThe actuators must be carefully 17, 1 218, 1319, by selectively may operate with controlled IJ21 blocking or enabling much lower energy * Acoustic nozzles. The ink * Acoustic lenses reflections in the ink pressure oscillation can be used to focus chamber must be may be achieved by the sound on the designed for vibrating the print nozzles head, or preferably by an actuator in the ink supply. Media The print head is * Low power + Precision * Silverbrook, EP proximity placed in close * High accuracy assembly required 0771 658 A2 and proximity to the print * Simple print head * Paper fibers may related patent medium. Selected construction cause problems applications drops protrude from * Cannot print on the print head further rough substrates than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. __________ Transfer Drops are printed to a * High accuracy * Bulky * Silverbrook, EP roller transfer roller instead * Wide range of * Expensive 0771 658 A2 and of straight to the print print substrates can * Complex related patent medium. A transfer be used construction applications roller can also be used * Ink can be dried * Tektronix hot for proximity drop on the transfer roller melt piezoelectric separation. ink jet *Any of thelU _____________________________________series WO 2006/099652 PCT/AU2005/000392 29 AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples Electro- An electric field is * Low power + Field strength + Silverbrook, EP static used to accelerate + Simple print head required for 0771 658 A2 and selected drops towards construction separation of small related patent the print medium. drops is near or applications above air + Tone-Jet breakdown Direct A magnetic field is + Low power + Requires + Silverbrook, EP magnetic used to accelerate + Simple print head magnetic ink 0771 658 A2 and field selected drops of construction + Requires strong related patent magnetic ink towards magnetic field applications the print medium. Cross The print head is Does not require Requires extemal * J06, IJ16 magnetic placed in a constant magnetic materials magnet field magnetic field. The to be integrated in Current densities Lorenz force in a the print head may be high, current carrying wire manufacturing resulting in is used to move the process electromigration actuator. problems Pulsed A pulsed magnetic Very low power Complex print as1 magnetic field is used to operation is possible head construction field cyclically attract a * Small print head * Magnetic paddle, which pushes size materials required in on the ink. A small print head actuator moves a catch, which selectively prevents the paddle from __________moving.__________ __________ __________ WO 2006/099652 PCT/AU2005/000392 30 ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator + Operational + Many actuator + Thermal Bubble mechanical simplicity mechanisms have Ink jet amplification is used. insufficient travel, + IJOl, 1J02, IJ06, The actuator directly or insufficient force, IJ07, IJ16, IJ25, drives the drop to efficiently drive IJ26 ejection process. the drop ejection process Differential An actuator material Provides greater High stresses are Piezoelectric expansion expands more on one travel in a reduced involved * J03, 1J09, 1J17, bend side than on the other. print head area Care must be 1J18, 1J19, IJ20, actuator The expansion may be taken that the 1J21, 1J22, IJ23, thermal, piezoelectric, materials do not IJ24, IJ27, 1J29, magnetostrictive, or delaminate IJ30, IJ3 1, IJ32, other mechanism. The Residual bend IJ33, IJ34, 1J35, bend actuator converts resulting from high 1J36, 1J37, 1J38, a high force low travel temperature or high 1J39, 1J42, 1J43, actuator mechanism to stress during IJ44 high travel, lower formation force mechanism. Transient A trilaye r bend * Very good + High stresses are * J40, J41 bend actuator where the two temperature stability involved actuator outside layers are * High speed, as a Care must be identical. This cancels new drop can be taken that the bend due to ambient fired before heat materials do not temperature and dissipates delaminate residual stress. The +Cancels residual actuator only responds stress of formation to transient heating of one side or the other. Reverse The actuator loads a * Better coupling * Fabrication * J05, Ul 11 spring spring. When the to the ink complexity actuator is turned off, * High stress in the the spring releases, spring 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 travel * Increased * Some stack actuators are stacked. *+Reduced drive fabrication piezoelectric ink jets This can be voltage complexity IJ04 appropriate where IIncreased actuators require high possibility of short electric field strength, circuits due to such as electrostatic pinholes and piezoelectric actuators.

WO 2006/099652 PCT/AU2005/000392 31 ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples Multiple Multiple smaller + Increases the + Actuator forces * J12, 1313, 1J18, actuators actuators are used force available from may not add 1J20, 1J22, 1328, simultaneously to an actuator linearly, reducing 1J42,1J43 move the ink. Each * Multiple efficiency actuator need provide actuators can be only a portion of the positioned to control force required. ink flow accurately Linear A linear spring is used * Matches low * Requires print IJ115 Spring to transform a motion travel actuator with head area for the with small travel and higher travel spring high force into a requirements longer travel, lower * Non-contact force motion. method of motion transformation Coiled A bend actuator is * Increases travel * Generally I 117, 132 1, 1334, actuator coiled to provide *+Reduces chip restricted to planar 35 greater travel in a area implementations reduced chip area. * Planar due to extreme implementations are fabrication difficulty relatively easy to in other orientations. fabricate. Flexure A bend actuator has a Simple means of +Care must be IJ2, IJ139, J133 bend small region near the increasing travel of taken not to exceed actuator fixture point, which a bend actuator the elastic limit in -flexes much more the flexure area readily than the * Stress remainder of the distribution is very actuator. The actuator uneven flexing is effectively Difficult to converted from an accurately model even coiling to an with finite element angular bend, resulting analysis in greater travel of the actuator tip. Catch The actuator controls a * Very low Complex trv10 small catch. The catch actuator energy construction either enables or Very small + Requires exte Ial disables movement of actuator size force an ink pusher that is h Unsuitable for controlled in a bulk pigmented inks ___________manner. Gears Gears can be used to Low force, low * Moving parts are pv13 increase travel at the travel actuators can required expense of duration, be used * Several actuator Circular gears, rack Can be fabricated cycles are required and pinion, ratchets, using standard More complex and other gearing surface MEMS drive electronics methods can be used. processes tComplex construction Friction, friction, and wear are flexesmu possible WO 2006/099652 PCT/AU2005/000392 32 ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples Buckle plate A buckle plate can be + Very fast + Must stay within + S. Hirata et al, used to change a slow movement elastic limits of the "An Ink-jet Head actuator into a fast achievable materials for long Using Diaphragm motion. It can also device life Microactuator", convert a high force, + High stresses Proc. IEEE MEMS, low travel actuator involved Feb. 1996, pp 418 into a high travel, + Generally high 423. medium force motion. power requirement + IJ18, IJ27 Tapered A tapered magnetic + Linearizes the + Complex + IJ14 magnetic pole can increase magnetic construction pole travel at the expense force/distance curve of force. Lever A lever and fulcrum is + Matches low + High stress + IJ32, IJ36, IJ37 used to transform a travel actuator with around the fulcrum motion with small higher travel travel and high force requirements into a motion with + Fulcrum area has longer travel and no linear movement, lower force. The lever and can be used for can also reverse the a fluid seal direction of travel. Rotary The actuator is + High mechanical + Complex + IJ28 impeller connected to a rotary advantage construction impeller. A small + The ratio of force + Unsuitable for angular deflection of to travel of the pigmented inks the actuator results in actuator can be a rotation of the matched to the impeller vanes, which nozzle requirements push the ink against by varying the stationary vanes and number of impeller out of the nozzle. vanes Acoustic A refractive or + No moving parts + Large area # 1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192 plate) acoustic lens is + Only relevant for + 1993 Elrod et al, used to concentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharp point is used + Simple + Difficult to + Tone-jet conductive to concentrate an construction fabricate using point electrostatic field. standard VLSI processes for a surface ejecting ink jet + Only relevant for electrostatic ink jets WO 2006/099652 PCT/AU2005/000392 33 ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the + Simple + High energy is + Hewlett-Packard expansion actuator changes, construction in the typically required to Thermal Ink jet pushing the ink in all case of thermal ink achieve volume + Canon Bubblejet directions. jet expansion. This leads to thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator moves in + Efficient + High fabrication + IJO1, IJ02, IJ04, normal to a direction normal to coupling to ink complexity may be IJ07, J111, IJ14 chip surface the print head surface. drops ejected required to achieve The nozzle is typically normal to the perpendicular in the line of surface motion movement. Parallel to The actuator moves + Suitable for + Fabrication + IJ12, IJ13, IJ15, chip surface parallel to the print planar fabrication complexity IJ33, , IJ34, IJ35, head surface. Drop + Friction IJ36 ejection may still be + Stiction normal to the surface. Membrane An actuator with a + The effective Fabrication 1982 Howkins push high force but small area of the actuator complexity USP 4,459,601 area is used to push a becomes the Actuator size stiff membrane that is membrane area Difficulty of in contact with the ink. integration in a VLSI process Rotary The actuator causes + Rotary levers Device * J05, 1J08, IJi3, the rotation of some may be used to complexity IJ28 element, such a grill or increase travel May have impeller + Small chip area friction at a pivot requirements point Bend The actuator bends + A very small Requires the 1970 Kyser et al when energized. This changing actuator to be made USP 3,946,398 may be due to dimensions can be from at least two 1973 Stemme differential thermal converted to a large distinct layers, or to USP 3,747,120 expansion, motion. have a thermal * u3, 1J09, IJ10, piezoelectric difference across the IJ19, IJ23, 1J24, expansion, actuator 1J25, J29,1J30, magnetostriction, or 1J31, 1133, IJ34, other form of relative IJ35 dimensional change. Swivel The actuator swivels * Allows operation * Inefficient I J06 around a central pivot, where the net linear coupling to the ink This motion is suitable force on the paddle motion where there are is zero opposite forces * Small chip area applied to opposite requirements sides of the paddle, e.g. Lorenz force. Straighten The actuator is Can be used with Requires careful J26, J32 normally bent, and shape memory balance of stresses straightens when alloys where the to ensure that the energized. austenic phase is quiescent bend is planar accurate WO 2006/099652 PCT/AU2005/000392 34 ACTUATOR MOTION Description Advantages Disadvantages Examples Double The actuator bends in One actuator can Difficult to make * J36, IJ37, IJ38 bend one direction when be used to power the drops ejected by one element is two nozzles. both bend directions energized, and bends Reduced chip identical. the other way when size. A small another element is Not sensitive to efficiency loss energized. ambient temperature compared to equivalent single bend actuators. Shear Energizing the Can increase the Not readily 1985 Fishbeck actuator causes a shear effective travel of applicable to other USP 4,584,590 motion in the actuator piezoelectric actuator material, actuators mechanisms Radial con- The actuator squeezes Relatively easy + High force 1970 Zoltan USP striction an ink reservoir, to fabricate single required 3,683,212 forcing ink from a nozzles from glass + Inefficient constricted nozzle. tubing as Difficult to microscopic integrate with VLSI structures - processes Coil /uncoil A coiled actuator * Easy to fabricate * Difficult to * IJl 7, 1J2 1, 1J34, uncoils or coils more as a planar VLSI fabricate for non- IJ35 tightly. The motion of process planar devices the free end of the Small area Poor out-of-plane actuator ejects the ink, required, therefore stiffness low cost Bow The actuator bows (or * Can increase the * Maximum travel * IJi 6, IJi 8, IJ27 buckles) in the middle speed of travel is constrained when energized. * Mechanically * High force rigid required Push-Pull Two actuators control * The structure is * Not readily * IJ 18 a shutter. One actuator pinned at both ends, suitable for ink jets pulls the shutter, and so has a high out-of- which directly push the other bushes it. plane rigidity the ink Curl A set of actuators curl * Good fluid flow * Design I J20, 1J42 inwards inwards to reduce the to the region behind complexity volume of ink that the actuator they enclose. increases efficiency Curl A set of actuators curl Relatively simple Relatively large 1J43 outwards outwards, pressurizing construction chip area ink in a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose * High efficiency High fabrication IJ22 a volume of ink. These * Small chip area complexity simultaneously rotate, fNot suitable for reducing the volume pigmented inks between the vanes.

WO 2006/099652 PCT/AU2005/000392 35 ACTUATOR MOTION Description Advantages Disadvantages Examples Acoustic The actuator vibrates The actuator can Large area 1993 Hadinioglu vibration at a high frequency. be physically distant required for et al, EUP 550,192 from the ink efficient operation 1993 Elrod et al, at useful frequencies EUP 572,220 *Acoustic coupling and crosstalk Complex drive circuitry Poor control of drop volume and position None In various ink jet No moving parts + Various other Silverbrook, EP designs the actuator tradeoffs are 0771658 A2 and does not move. required to related patent eliminate moving applications ________________________parts * Tone-jet WO 2006/099652 PCT/AU2005/000392 36 NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal way + Fabrication + Low speed + Thermal ink jet tension that ink jets are simplicity + Surface tension + Piezoelectric ink refilled. After the + Operational force relatively jet actuator is energized, simplicity small compared to + IJ01-IJ07, IJ10 it typically returns actuator force IJ14, IJ16, IJ20, rapidly to its normal + Long refill time IJ22-IJ45 position. This rapid usually dominates return sucks in air the total repetition through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle High speed Requires * 108, 1113, 1115, oscillating chamber is provided at Low actuator common ink 1117, IJ18, IJ19, ink pressure a pressure that energy, as the pressure oscillator IJ21 oscillates at twice the actuator need only May not be drop ejection open or close the suitable for frequency. When a shutter, instead of pigmented inks drop is to be ejected, ejecting the 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, as Requires two 1J09 actuator actuator has ejected a the nozzle is independent drop a second (refill) actively refilled actuators per nozzle actuator is energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive ink The ink is held a slight * High refill rate, * Surface spill * Silverbrook, EP pressure positive pressure. therefore a high must be prevented 0771 658 A2 and After the ink drop is drop repetition rate * Highly related patent ejected, the nozzle is possible hydrophobic print applications chamber fills quickly head surfaces are * Alternative for:, as surface tension and required IJ0-,IJ07, 1110-I14, ink pressure both IJ16, U20, IJ1922,45 operate to refill the nozzle.

WO 2006/099652 PCT/AU2005/000392 37 METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet channel + Design simplicity + Restricts refill + Thermal ink jet channel to the nozzle chamber + Operational rate + Piezoelectric ink is made long and simplicity + May result in a jet relatively narrow, + Reduces relatively large chip + IJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet + Only partially back-flow. effective Positive ink The ink is under a Drop selection Requires a Silverbrook, EP pressure positive pressure, so and separation method (such as a 0771 658 A2 and that in the quiescent forces can be nozzle rim or related patent state some of the ink reduced effective applications drop already protrudes Fast refill time hydrophobizing, or Possible from the nozzle. both) to prevent operation of the This reduces the flooding ofthe following: 1101 pressure in the nozzle ejection surface of 1107, 1109- 1112, chamber which is the print head. 1114, 1116, 1120, required to eject a IJ22, , 1J23-1134, certain volume of ink. IJ36- 1141, I144 The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more baffles * The refill rate is * Design * HP Thermal Ink are placed in the inlet not as restricted as complexity Jet ink flow. When the the long inlet * May increase * Tektronix actuator is energized, method. fabrication piezoelectric inkjet the rapid ink * Reduces complexity (e.g. movement creates crosstalk Tektronix hot melt eddies which restrict Piezoelectric print the flow through the heads). inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently * Significantly * Not applicable to Canon restricts disclosed by Canon, reduces back-flow most ink jet inlet the expanding actuator for edge-shooter configurations (bubble) pushes on a thermal inkjet t Increased flexible flap that devices fabrication restricts the inlet. complexity + Inelastic deformation of polymer flap results in creep over extended use WO 2006/099652 PCT/AU2005/000392 38 METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Inlet filter A filter is located Additional Restricts refill * J04, 1312, 1J24, between the ink inlet advantage of ink rate 1J27, U29, IJ30 and the nozzle filtration May result in chamber. The filter Ink filter may be complex has a multitude of fabricated with no construction small holes or slots, additional process restricting ink flow. steps The filter also removes particles which may block the nozzle. Small inlet The ink inlet channel * Design simplicity * Restricts refill * J02, 1337, IJ44 compared to the nozzle chamber rate to nozzle has a substantially IMay result in a smaller cross section relatively large chip than that of the nozzle area + resulting in easier ink Only partially egress out of the effective nozzle than out of the inlet. Inlet shutter A secondary actuator * Increases speed * Requires separate * J09 controls the position of of the ink-jet print refill actuator and a shutter, closing off head operation drive circuit the ink inlet when the main actuator is ___________energized. The inlet is The method avoids the + Back-flow Requires careful + IJO2, IJ03, IJ05, located problem of inlet back- problem is design to minimize J06, 07, IJO behind the flow by arranging the eliminated the negative 1311, IJ14, IJ16, ink-pushing ink-pushing surface of pressure behind the J22, 323, pt25, surface the actuator between paddle 132 8, 1J331, 1J332, the inlet and the ef33,fe34,ft35, nozzle. ta36, ou39, o340, I341 Part of the The actuator and a Significant Small increase in 107, R i20, s326, actuator wall of the ink reductions in back- fabrication an38 moves to chamber are arranged flow can be complexity shut off the so that the motion of achieved inlet the actuator closes off * Compact designs the inlet. possible Nozzle In some configurations Ink back-flow None related to Silverbrook, EP actuator of ink jet, there is no problem is ink back-flow on 0771658 A and does not expansion or eliminated actuation related patent result in ink movement of an applications back-flow actuator which may I Valve-jet cause ink back-flow * Tone-jet I through the inlet. theIJ33,_IJ34,_IJ35, WO 2006/099652 PCT/AU2005/000392 39 NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles are No added May not be Most inkjet nozzle firing fired periodically, complexity on the sufficient to systems before the ink has a print head displace dried ink * 30, J02,I103, chance to dry. When 1304, IJOS, 1J06, not in use the nozzles 1307,I109,IJ10, are sealed (capped) IJl1, 1312, IJ14, against air. 1316, 1320, IJ22, The nozzle firing is 1323, 1324, IJ25, usually performed 1326, 1327, 1328, during a special 1329,1U30, 1331, clearing cycle, after 1332, 133, 1334, first moving the print IJ36, U37, IJ38, head to a cleaning 1339, 1J40,, 1341, station. cJ42, o e43, ot44,, IJ45 Extra In systems which heat * Can be highly * Requires higher * Silverbrook, EP power to the ink, but do not boil effective if the drive voltage for 0771658 A2 and ink heater it under normal heater is adjacent to clearing related patent situations, nozzle the nozzle * May require applications clearing can be larger drive achieved by over- transistors powering the heater and boiling ink at the nozzle. Rapid The actuator is fired in * Does not require * Effectiveness * May be used success-ion rapid succession. In extra drive circuits depends with: J01, IJ02, of actuator some configurations, on the print head substantially upon 3IJO, IJ04, IJ05, pulses this may cause heat * Can be readily the configuration of 6IJO, IJ07, J109, build-up at the nozzle controlled and the ink jet nozzle IJ10, I11, IJ14, which boils the ink, initiated by digital IJ16, IJ20, IJ22, clearing the nozzle. in logic IJ23, IJ24, IJ25, other situations, it may IJ27, IJ28, IJ29, cause sufficient 0IJ2, IJ31, IJ32, vibrations to dislodge IJ33, IJ34, 136, clogged nozzles. IJ37, IJ38, IJ39, IJ340, IJ41, IJ42, station. _IJ2,IJ43, IJ44, 45 Extra Where an actuator is A simple Not suitable May be used power to not normally driven to solution where where there is a with: bi03, l309, ink pushing the limit of its motion, applicable hard limit to rma16, 120, 1323, actuator nozzle clearing may be actuator movement 1324, 1325, 1327, assisted by providing er29, -330, 1331, an enhanced drive 1332,+C39,a1340, signal to the actuator. IM41, 1342, it43, heaterisadja t t144,145 WO 2006/099652 PCT/AU2005/000392 40 NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Acoustic An ultrasonic wave is A high nozzle High U08, U13, 115, resonance applied to the ink clearing capability implementation cost U17, U18, U19, chamber. This wave is can be achieved if system does not IJ21 of an appropriate May be already include an amplitude and implemented at very acoustic actuator frequency to cause low cost in systems sufficient force at the which already nozzle to clear include acoustic blockages. This is actuators easiest to achieve if the ultrasonic wave is at a resonant frequency of the ink cavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EP clearing plate is pushed against severely clogged mechanical 0771 658 A2 and plate the nozzles. The plate nozzles alignment is related patent has a post for every required applications nozzle. A post moves * Moving parts are through each nozzle, required displacing dried ink. There is risk of damage to the nozzles *Accurate fabrication is required Ink The pressure of the ink May be effective Requires May be used pressure is temporarily where other pressure pump or with all 13 series ink pulse increased so that ink methods cannot be other pressure jets streams from all of the used actuator nozzles. This may be Expensive used in conjunction Wasteful of ink with actuator energizing. Print head A flexible 'blade' is Effective for Difficult to use if Many ink jet wiper wiped across the print planar print head print head surface is systems head surface. The surfaces non-planar or very blade is usually Low cost fragile fabricated from a Requires flexible polymer, e.g. mechanical parts rubber or synthetic iBlade can wear elastomer. out in high volume print systems Separate A separate heater is Can be effective Fabrication Can be used with ink boiling provided at the nozzle where other nozzle complexity many series ink heater although the normal clearing methods jets drop e-ection cannot be used mechanism does not * Can be require it. The heaters implemented at no do not require additional cost in individual drive some inkjet circuits, as many configurations nozzles can be cleared simultaneously, and no n imaging is required.m WO 2006/099652 PCT/AU2005/000392 41 NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages Examples Electro- A nozzle plate is + Fabrication High Hewlett Packard formed separately fabricated simplicity temperatures and Thermal Inkjet nickel from electroformed pressures are nickel, and bonded to required to bond the print head chip. nozzle plate *Minimum thickness constraints *Differential ____________ ~~thermal expansion __________ Laser Individual nozzle + No masks * Each hole must Canon Bubblejet ablated or holes are ablated by an required be individually 1988 Sercel et drilled intense UV laser in a + Can be quite fast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Some control Special Excimer Beam typically a polymer over nozzle profile equipment required Applications, pp. such as polyimide or is possible Slow where there 76-83 polysulphone + Equipment are many thousands 1993 Watanabe required is relatively of nozzles per print et al., USP low cost head 5,208,604 May produce thin ____________ ____________________burrs it exit holes ___________ Silicon A separate nozzle High accuracy is Two part rK. Bean, IEEE micro- plate is attainable construction Transactions on machined micromachined from High cost Electron Devices, single crystal silicon, Requires Vol. ED-25, No. 10, and bonded to the precision alignment 1978, pp 1185-1195 print head wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins et al., USP 4,899,181 Glass Fine glass capillaries * No expensive * Very small * 1970 Zoltan USP capillaries are drawn from glass equipment required nozzle sizes are 3,683,212 tubing. This method Simple to make difficult to form has been used for single nozzles Not suited for making individual mass production nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is *+High accuracy Requires Silverbrook, EP surface deposited as a layer (<1 rim) sacrificial layer 0771658 A and micro- using standard VLSI Monolithic under the nozzle related patent machined deposition techniques. Low cost plate to form the applications using VLSI Nozzles are etched in * Existing nozzle chamber * IJO 1, 1J02, 1J04, itho- the nozzle plate using processes can be * Surface may be IJI 1, J12, ei17, graphic VLSI lithography and used fragile to the touch IJ18, 1J20, 1122, processes etching. 124,V J27, 1J28, 129, 30 1J391, + X32,33, 1J34, IJ36, 1137, 1138, IJ39, 1140, 1141, clogedbadhsiv Hawk__insJ42, ea43, UJ44 WO 2006/099652 PCT/AU2005/000392 42 NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Monolithic, The nozzle plate is a + High accuracy + Requires long + IJ03, IJ05, IJ06, etched buried etch stop in the (<1 pm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle + Monolithic + Requires a IJ1O, IJ13, IJ14, substrate chambers are etched in * Low cost support wafer IJ15, IJ16, IJ19, the front of the wafer, * No differential IJ2 1, IJ23, IJ25, and the wafer is expansion IJ26 thinned from the back side. Nozzles are then etched in the etch stop layer. No nozzle Various methods have * No nozzles to Difficult to Ricoh 1995 plate been tried to eliminate become clogged control drop Sekiya et al USP the nozzles entirely, to position accurately 5,412,413 prevent nozzle Crosstalk 1993 Hadinioglu clogging. These problems et al ELP 550,192 include thermal bubble 1993 Elrodetal mechanisms and EUP 572,220 acoustic lens mechanisms Trough Each drop ejector has * Reduced * Drop firing I J35 a trough through manufacturing direction is sensitive which a paddle moves, complexity to wicking. There is no nozzle * Monolithic plate. Nozzle slit The elimination of NO nozzles to * Difficult to 4 1989 Saito et al instead of nozzle holes and become clogged control drop USP 4,799,068 individual replacement by a slit position accurately nozzles encompassing many c xCrosstalk actuator positions problems reduces nozzle clogging, but increases crosstalk due to ink surface waves DROP EJECTION DIRECTION SDescription Advantages Disadvantages Examples Edge Ink flow is along the Simple Nozzles limited Canon Bubblejet ('edge surface of the chip, construction to edge 1979 Endo et al GB shooter') and ink drops are * No silicon * High resolution patent 2,007,162 ejected from the chip etching required is difficult * Xerox heater-in edge. Good heat Fast color pit 1990 Hawkins et sinking via substrate printing requires al USP 4,899,181 Mechanically one print head per Tone-jet strong color * Ease of chip handing Surface Ink flow is along the * No bulk silicon * Maximum ink * Hewlett-Packard ('roof surface of the chip, etching required flow is severely TIJ 1982 Vaught et shooter') and ink drops are Silicon can make restricted al USP 4,490,728 ejected from the chip an effective heat * J02, IJI1,J12, surface, normal to the sink J20,J22 plane of the chip. Mechanical onstrengthi WO 2006/099652 PCT/AU2005/000392 43 DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Through Ink flow is through the * High ink flow Requires bulk Silverbrook, EP chip, chip, and ink drops are * Suitable for silicon etching 0771658 A2 and forward ejected from the front pagewidth print related patent ('up surface of the chip. heads applications shooter') + High nozzle * J04, UJ17, UJ18, packing density IJ24, IJ27-IJ45 therefore low manufacturing cost Through Ink flow is through the * High ink flow * Requires wafer U01J~, IJ03, IJ05, chip, chip, and ink drops are * Suitable for thinning 1J06, 1J07, 1J08, reverse ejected from the rear pagewidth print * Requires special 1J09, U1, e13, ('down surface of the chip. heads handling during 1J14, 1J15, IJ16, shooter') + High nozzle manufacture +J19, IJ21, IJ23, packing density IJ25, IJ26 therefore low manufacturing cost Through Ink flow is through the * Suitable for Pagewidth print Epson Stylus actuator actuator, which is not piezoelectric print heads require Tektronix hot fabricated as part of heads several thousand melt piezoelectric the same substrate as connections to drive inkjets the drive transistors, circuits *Cannot be manufactured in standard CMOS fabs + Complex Assembly required WO 2006/099652 PCT/AU2005/000392 INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink which * Environmentally + Slow drying + Most existing ink dye typically contains: friendly + Corrosive jets water, dye, surfactant, * No odor + Bleeds on paper + All IJ series ink humectant, and + May jets biocide. strikethrough + Silverbrook, EP Modem ink dyes have + Cockles paper 0771 658 A2 and high water-fastness, related patent light fastness applications Aqueous, Water based ink which * Environmentally Slow drying IJ02, 1J04, 1J2 1, pigment typically contains: friendly Corrosive 1J26, 1J27, IJ30 water, pigment, * No odor Pigment may Silverbrook, EP surfactant, humectant, * Reduced bleed clog nozzles 0771658 A2 and and biocide. Reduced wicking Pigment may related patent Pigments have an Reduced clog actuator applications advantage in reduced strikethrough mechanisms Piezoelectric ink bleed, wicking and Cockles paper jets strikethrough. * Thermal ink jets (with significant restrictions) Methyl MEK is a highly * Very fast drying * Odorous * All IJ series ink Ethyl volatile solvent used Prints on various Flammable jets Ketone for industrial printing substrates such as (MEK) on difficult surfaces metals and plastics such as aluminum ____________cans. Alcohol Alcohol based inks * Fast drying * Slight odor * All IJ series ink (ethanol,' 2- can be used where the * Operates at sub- * Flammable jets butanol, printer must operate at freezing and others) temperatures below temperatures the freezing point of +Reduced paper water. An example of cockle this is in-camera CLow cost consumer photographic printing. Phase The ink is solid at * No drying time- * High viscosity * Tektronix hot change room temperature, and ink instantly freezes Printed ink melt piezoelectric (hot melt) is melted in the print on the print medium typically has a ink jets head before jetting. Almost any print 'waxy' feel r1989 Nowak Hot melt inks are medium can be used * Printed pages USP 4,820,346 usually wax based, + No paper cockle may 'block' All IJ series ink with a melting point occurs Ink temperature jets around 80 *C. After * No wicking may be above the jetting the ink freezes occurs curie point of almost instantly upon mNo bleed occurs permanent magnets contacting the print No strikethrough Ink heaters medium or a transfer occurs consume power roller. AnLong warm-up cons rtime WO 2006/099652 PCT/AU2005/000392 45 INK TYPE Description Advantages Disadvantages Examples Oil Oil based inks are * High solubility High viscosity: All U series ink extensively used in medium for some this is a significant jets offset printing. They dyes limitation for use in have advantages in + Does not cockle ink jets, which improved paper usually require a characteristics on * Does not wick low viscosity. Some paper (especially no through paper short chain and wicking or cockle). multi-branched oils Oil soluble dies and have a sufficiently pigments are required. low viscosity. *Slow drying Micro- A microemulsion'is a * Stops ink bleed * Viscosity higher * All IJ series ink emulsion stable, self forming * High dye than water jets emulsion of oil, water, solubility Cost is slightly and surfactant. The * Water, oil, and higher than water characteristic drop size amphiphilic soluble based ink is less than 100 run, dies can be used * High surfactant and is determined by Can stabilize concentration the preferred curvature pigment required (around of the surfactant. suspensions 5%)

Claims

1. A printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle, wherein the surface formations are configured in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface, thereby isolating each nozzle from at least one adjacent nozzle

2. The printhead of claim 1, wherein the surface formations each have a hydrophobic surface.

3. The printhead of claim 1, wherein each nozzle enclosure further comprises a roof spaced apart from the respective nozzle aperture, the roof having a roof opening aligned with its respective nozzle aperture, thereby allowing ejected ink droplets to pass therethrough onto the print medium.

4. The printhead of claim 3, wherein the sidewalls extend from each roof to the ink ejection surface.

5. The printhead of claim 4, wherein the sidewalls extend from a perimeter region of each roof.

6. The printhead of claim 1, which is a pagewidth inkjet printhead.

7. The printhead of claim 1, wherein the printhead has a nozzle density sufficient to print at up to 1600 dpi. FIN 47

8. A printer comprising the printhead according to claim 1.

9. A method of printing from the printhead of claim 1, whilst minimizing cross contamination of ink between adjacent nozzles, the method comprising the steps of: (a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle, wherein the surface formations are configured in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface, thereby isolating each nozzle from at least one adjacent nozzle; and (b) printing onto a print medium using said printhead.

10. A method of fabricating the printhead of claim 1 having isolated nozzles, the method comprising the steps of: (a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; (b) depositing a layer of photoresist over the ink ejection surface; (c) defining recesses in the photoresist, each recess revealing a portion of the ink ejection surface surrounding a respective nozzle aperture; (d) depositing a roof material over the photoresist and into the recesses; (e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and (f) removing the photoresist. FIN