Injet printhead with thermal bend arm exposed to ink flow

• US 7,328,975 B2
• Filed: 08/23/2004
• Issued: 02/12/2008
• Est. Priority Date: 07/15/1997
• Status: Expired due to Fees

• Current Assignee: Memjet Technology Ltd. (Memjet Limited)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia
• Primary Examiner(s): STEPHENS, JUANITA DIONNE
• Application Number:
  US10/922,880
• Publication Number:
  US 20050264612A1
• Time in Patent Office: 1,268 Days
• Field of Search: 347/20, 347/54, 347/56, 347 61- 65, 347/67, 60527-529
• US Class Current: 347/53
• CPC Class Codes: B41J 2/135 Nozzles
• CPC Class Codes: B41J 2/14314 Structure of ink jet print heads with electrostatically actuated membrane
• CPC Class Codes: B41J 2/14427 Structure of ink jet print heads with thermal bend detached actuators
• CPC Class Codes: B41J 2/1623 bonding and adhesion
• CPC Class Codes: B41J 2/1626 etching
• CPC Class Codes: B41J 2/1628 dry etching
• CPC Class Codes: B41J 2/1629 wet etching
• CPC Class Codes: B41J 2/1631 photolithography
• CPC Class Codes: B41J 2/1632 machining
• CPC Class Codes: B41J 2/1635 dividing the wafer into individual chips
• CPC Class Codes: B41J 2/1637 molding
• CPC Class Codes: B41J 2/1639 sacrificial molding
• CPC Class Codes: B41J 2/1642 thin film formation by CVD [chemical vapor deposition]
• CPC Class Codes: B41J 2/1643 thin film formation by plating
• CPC Class Codes: B41J 2/1645 thin film formation by spincoating
• CPC Class Codes: B41J 2/1646 thin film formation by sputtering
• CPC Class Codes: B41J 2/1648 Production of print heads with thermal bend detached actuators
• CPC Class Codes: B41J 2/16585 for paper-width or non-reciprocating print heads
• CPC Class Codes: B41J 2/17513 Inner structure
• CPC Class Codes: B41J 2/17596 Ink pumps, ink valves
• CPC Class Codes: B41J 2002/041 : Electromagnetic transducer
• CPC Class Codes: B41J 2002/14346 : Ejection by pressure produced by thermal deformation of ink chamber, e.g. buckling
• CPC Class Codes: B41J 2002/14435 : Moving nozzle made of thermal bend detached actuator
• CPC Class Codes: B41J 2202/21 : Line printing
• CPC Class Codes: G06F 21/79 : in semiconductor storage media, e.g. directly-addressable memories
• CPC Class Codes: G06F 21/86 : Secure or tamper-resistant housings
• CPC Class Codes: G06F 2221/2129 : Authenticate client device independently of the user
• CPC Class Codes: G06K 1/121 : by printing code marks applying code marks to labels B65C9/46; marking or coding completed packages B65B61/26
• CPC Class Codes: G06K 19/06037 : multi-dimensional coding
• CPC Class Codes: G06K 7/14 : using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1417 : 2D bar codes
• CPC Class Codes: H04N 23/00 : Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: H04N 5/2628 : Alteration of picture size, shape, position or orientation, e.g. zooming, rotation, rolling, perspective, translation

Abstract

An inkjet drop ejection apparatus 1010 having a chamber 1012 with a nozzle 1011; and an actuator with a thermal bend arm 1034. The arm has a cold portion 1024 and a hot portion 1022 such that thermal expansion of the hot portion bends the arm. The cold portion is positioned for greater exposure to ink flow than the hot portion. The heat generated by the hot portion of the thermal bend arm can heat up the cold portion. As the cold portion heats, it expands thereby forcing the hot portion to heat to a higher temperature to achieve the same expansion differential that provides the required bend in the arm. By positioning the cold portion for greater exposure to the ink flow, it dissipates heat to the ink and its temperature is more stable. This in turn improves the efficiency of the arm and the entire printhead.

Claims

1. An inkjet drop ejection apparatus comprising:

a chamber with a nozzle; and

,

an actuator with a thermal bend arm having a cold portion and a hot portion such that thermal expansion of the hot portion bends the arm;

wherein,

the cold portion is positioned for greater exposure to ink flow than the hot portion.

2. An inkjet drop ejection apparatus as claimed in claim 1 wherein at least part of the hot portion in a recess formed in the chamber, the recess formed such that the hot portion is removed from the main ink flow path.

3. An inkjet drop ejection apparatus as claimed in claim 2 wherein the actuator further comprises a vane mounted for reciprocating movement within the chamber, the vane formed from magnetic material such that a pulsing externally applied magnetic field causes the reciprocating movement that ejects ink from the nozzle;

wherein, the thermal bend arm is configured for bending into the chamber to prevent movement of the vane by the pulsing magnetic field.

4. An inkjet drop ejection apparatus as claimed in claim 3 wherein the recess is a channel and one end of the thermal bend arm is mounted at one end of the channel such that in its quiescent state, the arm is within the channel, and when activated the arm bends such that the distal end of the arm moves out of the channel.

5. An inkjet drop ejection apparatus as claimed in claim 4 wherein the distal end has a stop formation for engaging the vane and preventing it from movement.

6. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises an electrothermal heater positioned for heating ink in said chamber to a temperature above the boiling point of the ink, causing a bubble to form in order to eject a drop of the ink from said nozzle.

7. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises an piezoelectric crystal adapted to expand, shear or bend to apply pressure to the ink, in order to eject drops of the ink from said nozzle.

8. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has relaxor materials and is adapted to produce an electric field wherein the electric field activates electrostriction in the relaxor materials in order to eject drops of the ink from said nozzle.

9. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator material has an antiferroelectric and a ferroelectric phase, wherein applying an electric field to the actuator material results in a transition from the antiferroelectric to the ferroelectric phase in order to eject drops of the ink from said nozzle.

10. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises conductive plates which are separated by a compressible or fluid dielectric, such that applying a voltage to said plates causes said plates to attract each other and displace ink, said displacement resulting in ejection of ink drops from said nozzle.

11. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator is adapted to apply a strong electric field to the ink, whereupon electrostatic attraction accelerates the drops of ink towards a print medium.

12. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises an electromagnet and a permanent magnet, wherein the electromagnet is configured to directly attract a permanent magnet, to cause ejection of, or assists the ejection of ink from said nozzle.

13. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a soft magnetic core and a solenoid adapted to induce a magnetic field in the soft magnetic core, the soft magnetic core having two parts spaced apart such that inducing a magnetic field in the soft magnetic core causes said two parts to attract each other, to cause ejection of or assist the ejection of, ink from said nozzle.

14. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator is adapted to use a Lorenz force acting on said actuator to cause ejection of, or assist the ejection of ink from said nozzle.

15. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator includes material that exhibit giant magnetostrictive effect, wherein the actuator is adapted to use the giant magnetostrictive effect to cause ejection of, or assist the ejection of ink from said nozzle.

16. An inkjet drop ejection apparatus as claimed in claim 1 wherein the nozzle, the chamber and the actuator are configured for retaining ink in the chamber under positive pressure by surface tension at the nozzle, such that activation of the actuator reduces said surface tension of the ink below a drop forming threshold to cause said ink to egress from said nozzle.

17. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is adapted to locally reduce the ink viscosity in the nozzle when the nozzle is selected to eject ink, such that said reduction of viscosity aids in the ejection of ink from said nozzle.

18. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is adapted to generate an acoustic wave which is focused upon a region in the nozzle from which a drop is to be ejected.

19. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is adapted to use differential thermal expansion upon Joule heating to cause ejection of, or assist the ejection of ink from said nozzle.

20. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a material with a very high coefficient of thermal expansion, such that thermal expansion of the actuator causes ejection of, or assists the ejection of, ink from said nozzle.

21. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a polymer with a high coefficient of thermal expansion which is doped with conducting substances to increase its conductivity such that resistively heating the actuator results in mechanical motion which ejects or assists in ejecting ink from said nozzle.

22. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a shape memory alloy capable of thermal switching between its martensitic state and its austenic state, the switching between states causing the actuator to change shape in order to cause ejection of, or assist in causing ejection of, ink from said nozzle.

23. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is a linear magnetic actuator, wherein activation of the actuator causes ejection of, or assists in causing ejection of, ink from said nozzle.

24. An inkjet drop ejection apparatus as claimed in claim 1 wherein during use, activation of said actuator supplies sufficient kinetic energy to the ink in the chamber to expel a drop of ink from said nozzle.

25. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators wherein selectively energizing one of the actuators causes ejection of a drop from the corresponding nozzle wherein the drop is separated from the ink in said nozzle by contact with a print medium or a transfer roller.

26. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators wherein selectively energizing one of the actuators causes ejection of a drop from the corresponding nozzle wherein the drop is separated from the ink in said nozzle by a strong electric field.

27. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators wherein selectively energizing one of the actuators causes ejection of a drop from the corresponding nozzle wherein the drop is separated from the ink in said nozzle by a strong magnetic field.

28. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has a shutter for selectively blocking ink flow to said nozzle, such that during use, the apparatus ejects drops at a drop ejection frequency and creates pressure pulses in the ink at a frequency that is a multiple of the drop ejection frequency, wherein the shutter opens to eject a drop when the ink is under positive pressure from a pulse and the shutter closes to prevent ink ejection from the nozzle.

29. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a shutter and a grill, wherein moving the shutter closes at least one aperture in the grill to block ink supply to the nozzle.

30. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a catch and an ink pusher, wherein the ink pusher is adapted to move such that the drops of ink are ejected from the nozzle and the actuator is adapted to control the catch to prevent the ink pusher from moving when a drop is not to be ejected.

31. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is capable of directly firing the ink drops from said nozzle, without the assistance of an external field.

32. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators, the apparatus adapted to oscillate the pressure of the ink to provide much of the required energy to eject drops from said nozzle, and wherein said actuator selects which of the nozzles are to eject ink drops are to be fired by selectively blocking or enabling nozzles.

33. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators, and is adapted to select one or more of the nozzles to effect printing on a print medium spaced from, and moved relative to the nozzles, wherein the actuators of the nozzles that are selected cause ink drops to protrude from said nozzle further than the ink drops of the nozzles that are not selected, such that the ink drops protruding from nozzles that are selected contact the print medium, and soak into said print medium fast enough to cause separation of said selected drops from ink remaining in said nozzle.

34. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a transfer roller wherein the ink drops are printed to the transfer roller.

35. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators, and is adapted to select one or more of the nozzles to effect printing on a print medium spaced from, and moved relative to the nozzles, the ejection apparatus being adapted to generate an electric field to accelerate ink drops from the nozzles that are selected towards a print medium.

36. An inkjet drop ejection apparatus as claimed in claim 1 wherein the ink drops are magnetic and the apparatus further comprises an array of the nozzles, each nozzle corresponding to one of the chambers and one of the actuators, and is adapted to select one or more of the nozzles to effect printing on a print medium spaced from, and moved relative to the nozzles, the ejection apparatus being adapted to generate a magnetic field to accelerate the magnetic ink drops from selected nozzles towards a print medium.

37. An inkjet drop ejection apparatus as claimed in claim 1 wherein during use, said drop ejection apparatus is placed in a constant magnetic field, and Lorenz force in a current carrying wire is used to move said actuator.

38. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has a paddle which pushes on ink in the chamber to eject the ink drops from said nozzle, and a catch for selectively preventing said paddle from moving, such that during use, said drop ejection apparatus is placed in a pulsed magnetic field to cyclically move the paddle when it is not held by the catch.

39. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator moves to directly effect ejection of the ink drops without any mechanical amplification of the actuator motion.

40. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is a differential expansion bend actuator capable of converting a high force, low travel mechanism to high travel, lower force mechanism.

41. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is a trilayer bend actuator where the two outside layers are substantially identical.

42. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has a spring and a mechanism to load the spring such that when the mechanism is deactivated, the spring releases to eject the ink drops.

43. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a stacked series of thin thermal bend actuators.

44. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises multiple smaller actuators adapted to operate simultaneously to move the ink drops.

45. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has a linear spring for transforming a motion with small travel and high force into a longer travel, lower force motion.

46. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is a coiled bend actuator.

47. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is a bend actuator cantilevered into the chamber from a fixed end, wherein the actuator has a region near the fixed end that flexes more readily than the remainder of said actuator.

48. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has an ink pusher for ejecting the drops of ink, and a controllable catch for to releasably engaging the ink pusher to prevent its movement and thereby the ejection of the drops of ink.

49. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has components operatively coupled by gears such that travel of one component causes an increased travel in another component.

50. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has a moveable part and a buckle plate such that movement of the moveable part results in movement with increased speed or travel of a part of the buckle plate.

51. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a tapered magnetic pole.

52. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has a moveable part, and a lever and fulcrum for transforming the motion of the moveable part.

53. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus further comprises a rotary impellor, wherein the rotary impeller is connected to the actuator.

54. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has an acoustic lens and is adapted to generate sound waves such that the acoustic lens concentrates the sound waves.

55. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has a sharp point for concentrating an electrostatic field to cause or assist ink drop ejection from said nozzle.

56. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has a variable volume such that the volume of the actuator is increased in order to eject the ink drop from the nozzle.

57. An inkjet printhead comprising a substrate surface and an array of inkjet drop ejection apparatuses as claimed in claim 1, wherein the nozzles of the array are formed in the surface and the actuators move in a direction normal to the surface.

58. An inkjet printhead comprising a substrate surface and an array of inkjet drop ejection apparatuses as claimed in claim 1, wherein the nozzles of the array are formed in the surface and the actuators move in a direction parallel to the surface.

59. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has a stiff membrane configured for contact with ink in said chamber and the actuator is configured for pushing the stiff membrane.

60. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is adapted to rotate an element of said drop ejection apparatus.

61. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator bends when energized.

62. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a pivot, wherein said actuator swivels around the pivot when energized.

63. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is normally bent, and straightens when energized.

64. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has two elements, such that the actuator bends in one direction when one element is energized, and bends in an opposing direction when the other element is energized.

65. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has material that deforms in a shear motion when energized.

66. An inkjet drop ejection apparatus as claimed in claim 1 further comprising an ink reservoir in said chamber wherein said actuator is adapted to squeeze the ink reservoir.

67. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is coiled, and either coils further, or uncoils when energized.

68. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator has a middle region that bows or buckles when the actuator is energized.

69. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a shutter and two controlling actuators, one of the controlling actuators pulls said shutter, and the other controlling actuator pushes said shutter.

70. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a set of actuator members configured to enclose a volume of ink, the actuator members curl when energized to reduce the volume of ink that said set of actuators enclose.

71. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator comprises a set of actuator members which curl when energized to pressurize ink in said chamber surrounding said set of actuator members, and eject ink from said nozzle.

72. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator comprises a plurality of vanes configured for enclosing a volume of ink between adjacent vanes, the actuator adapted to simultaneously rotate said vanes when energized in order to reduce the volume of ink between adjacent vanes.

73. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator is adapted to vibrate at a high frequency.

74. An inkjet drop ejection apparatus as claimed in claim 1 wherein said actuator does not move relative to the chamber as it causes ejection of, or assists in causing ejection of, ink from said nozzle.

75. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber, the actuator and the nozzle are configured such that ink refills the chamber after drop ejection by the surface tension of the ink.

76. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator has a moveable shutter to impede ink flow from the chamber and the apparatus adapted to cyclically apply pressure to the ink, such that during use, ink refills the chamber after drop ejection by a cycle of positive ink pressure, and said chamber is prevented from emptying during a subsequent cycle of negative ink pressure by the moveable shutter.

77. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a second actuator for refilling the chamber with ink.

78. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to maintain the ink at a slight positive pressure, wherein during use, ink refills the chamber refills through a combination of both the surface tension of the ink and the slight positive ink pressure.

79. An inkjet drop ejection apparatus as claimed in claim 1 further comprising an ink inlet channel to the chamber, the ink inlet channel being long and narrow relative to the dimensions of the chamber such that ink in said chamber is restricted from flowing out during ink drop ejection by viscous drag from the ink inlet channel.

80. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet, the apparatus adapted to maintain the ink at a positive pressure, wherein during use, ink in said chamber is restricted from flowing out of the ink inlet during drop ejection by the positive ink pressure.

81. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet and one or more baffles, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet by the one or more baffles.

82. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet and a flexible flap, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet by the flexible flap.

83. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet and a filter, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet by the a filter.

84. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet with a cross sectional area smaller than the cross sectional area of said nozzle, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet.

85. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a shutter and a second actuator for operating the shutter, and wherein the chamber has an ink inlet such that ink in said chamber is restricted from flowing out of the ink inlet during drop ejection by the shutter.

86. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet an ink pushing surface, the ink inlet positioned close to the ink pushing surface, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet by the ink pushing surface.

87. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet and the actuator has a part adapted to close the inlet when the actuator is energized, such that during drop ejection, ink in said chamber is restricted from flowing out of the ink inlet.

88. An inkjet drop ejection apparatus as claimed in claim 1 wherein the chamber has an ink inlet and the actuator is configured such that ink in the chamber is not urged to flow out of the ink inlet during drop ejection.

89. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to periodically eject ink from the nozzle, before the ink has time to dry, for preventing ink from drying out in said nozzle.

90. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to provide more energy to said actuator than is normally used for drop ejection, for clearing dried or partially dried ink in said nozzle.

91. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to energize said actuator in rapid succession for clearing dried or partially dried ink in said nozzle.

92. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to provide an enhanced drive to said actuator for clearing dried or partially dried ink in said nozzle.

93. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to apply an ultrasonic wave to said ink chamber for clearing dried or partially dried ink in said nozzle.

94. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a microfabricated plate with a plurality of posts, such that moving the microfabricated plate toward the nozzle inserts one of the posts into the nozzle, to clear dried or partially dried ink in said nozzle.

95. An inkjet drop ejection apparatus as claimed in claim 1 further adapted to temporarily increase the pressure in the chamber such that ink streams from the nozzle to clear dried or partially dried ink from said nozzle.

96. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a flexible blade adapted to wipe across the nozzle surface to clear dried or partially dried ink from said nozzle.

97. An inkjet drop ejection apparatus as claimed in claim 1 further comprising a heater at the nozzle for clearing dried or partially dried ink in said nozzle by energizing the heater, wherein said heater does not cause or assist the ejection of ink drops.

98. An inkjet drop ejection apparatus as claimed in claim 1 wherein the nozzle is formed in a plate fabricated from electroformed nickel.

99. An inkjet drop ejection apparatus as claimed in claim 1 wherein said nozzle is an aperture formed by laser ablation.

100. An inkjet drop ejection apparatus as claimed in claim 1 wherein the nozzle is formed in a plate that is microfabricated from silicon.

101. An inkjet drop ejection apparatus as claimed in claim 1 wherein said nozzle is formed from a glass capillary.

102. An inkjet drop ejection apparatus as claimed in claim 1 wherein the nozzle is formed in a surface deposited as a layer using VLSI deposition techniques, wherein the nozzle is etched in said surface.

103. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus is formed on and through a substrate, and the nozzle is formed in a layer that is embedded in the substrate wherein said nozzle is etched in said layer.

104. An inkjet drop ejection apparatus as claimed in claim 1 wherein said nozzle is a virtual nozzle, the virtual nozzle being a location on the apparatus from where drops are ejected by acoustic concentration or inertial confinement, wherein the virtual nozzle is formed on demand when an ink drop is to be ejected.

105. An inkjet drop ejection apparatus as claimed in claim 1 wherein said nozzle is at least partially defined by the walls of a trough and the actuator is a paddle adapted to move through the trough.

106. An inkjet drop ejection apparatus as claimed in claim 1 wherein said nozzle is in the form of a slit and has a plurality of the actuators for ejecting drops.

107. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus is formed on and through a substrate, and the drops of ink are ejected from the edge of the substrate.

108. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus is formed on and through a substrate, and the nozzle is formed in a surface of the substrate such that the drops of ink are ejected normal to the surface.

109. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus is formed on and through a substrate, the nozzle is formed on a front surface of the substrate such that ink flows through the substrate, and ink drops are ejected from the front surface.

110. An inkjet drop ejection apparatus as claimed in claim 1 wherein the apparatus is formed on and through a substrate, the nozzle is formed on a rear surface of the substrate such that ink flows through the substrate, and ink drops are ejected from the rear surface.

111. An inkjet drop ejection apparatus as claimed in claim 1 wherein the actuator is configured such that ink flows through the actuator when ejecting drops.

112. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises water and a colorant comprising a dye.

113. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises water and a colorant comprising a pigment.

114. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises methyl ethyl ketone.

115. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises an alcohol.

116. An inkjet drop ejection apparatus as claimed in claim 1 wherein the ink is solid at room temperature, and is melted before ejection from said nozzle.

117. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises an oil.

118. An inkjet drop ejection apparatus as claimed in claim 1 wherein said ink comprises a microemulsion.

119. An office printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

120. A short run digital printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

121. A high speed digital printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

122. A notebook computer incorporating a printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

123. An offset press supplemental printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

124. A pagewidth printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

125. A portable printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

126. A copier comprising an inkjet drop ejection apparatus as claimed in claim 1.

127. A facsimile machine comprising an inkjet drop ejection apparatus as claimed in claim 1.

128. A label printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

129. A large format printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

130. A photograph copier comprising an inkjet drop ejection apparatus as claimed in claim 1.

131. A digital photographic minilab incorporating a printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

132. A video printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

133. A PDA incorporating a printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

134. A wallpaper printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

135. An indoor sign printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

136. A billboard printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

137. A fabric printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

138. A camera printer comprising an inkjet drop ejection apparatus as claimed in claim 1.

139. A commercial printer array comprising an inkjet drop ejection apparatus as claimed in claim 1.