Inkjet nozzle assembly having moving roof portion defined by a thermal bend actuator having a plurality of cantilever beams

1. An inkjet nozzle assembly comprising:

a nozzle chamber comprising a floor and a roof, said roof having a nozzle opening defined therein, said roof having a moving portion moveable towards the floor; and

a thermal bend actuator, having a plurality of cantilever beams, for ejecting ink through the nozzle opening, said actuator comprising:

a first active beam for connection to drive circuitry; and

a second passive beam mechanically cooperating with the first beam, such that when a current is passed through the first beam, the first beam expands relative to the second beam, resulting in bending of the actuator,

wherein said moving portion comprises the actuator, and wherein the first active beam defines at least 30% of a total area of the roof.

2. The inkjet nozzle assembly of claim 1 , wherein the first active beam defines at least part of an exterior surface of said roof.

3. The inkjet nozzle assembly of claim 1 , wherein the nozzle opening is defined in the moving portion, such that the nozzle opening is moveable relative to the floor portion.

4. The inkjet nozzle assembly of claim 1 , wherein the actuator is moveable relative to the nozzle opening.

5. The inkjet nozzle assembly of claim 1 , wherein the first beam is defined by a tortuous beam element, said tortuous beam element having a plurality of contiguous beam members.

6. The inkjet nozzle assembly of claim 5 , wherein the plurality of contiguous beam members comprises a plurality of longer beam members extending along a longitudinal axis of the first beam, and at least one shorter beam member extending across a transverse axis of the first beam and interconnecting longer beam members.

7. The inkjet nozzle assembly of claim 1 , wherein one of said plurality of beams is comprised of a porous material.

8. The inkjet nozzle assembly of claim 7 , wherein said porous material is porous silicon dioxide having a dielectric constant of 2 or less.

9. The inkjet nozzle assembly of claim 1 , wherein the thermal bend actuator further comprises a third insulation beam sandwiched between the first beam and the second beam.

10. The inkjet nozzle assembly of claim 9 , wherein the third insulation beam is comprised of a porous material.

11. The inkjet nozzle assembly of claim 1 , wherein the first beam is fused or bonded to the second beam.

12. The inkjet nozzle assembly of claim 11 , wherein the second beam is comprised of a porous material.

13. The inkjet nozzle assembly of claim 1 , wherein at least part of the first beam is spaced apart from the second beam.

14. The inkjet nozzle assembly of claim 1 , wherein the first beam is comprised of a material selected from the group comprising: titanium nitride, titanium aluminium nitride and an aluminium alloy.

15. The inkjet nozzle assembly of claim 1 , wherein the first beam is comprised of an aluminium alloy.

16. The inkjet nozzle assembly of claim 15 , wherein said aluminium alloy comprises aluminium and at least one other metal having a Young's modulus of more than 100 GPa.

17. The inkjet nozzle assembly of claim 16 , wherein said at least one metal is selected from the group comprising: vanadium, manganese, chromium, cobalt and nickel.

18. The inkjet nozzle assembly of claim 15 , wherein said alloy comprises aluminum and vanadium.

19. The inkjet nozzle assembly of claim 15 , wherein said alloy comprises at least 80% aluminium.