Thermal bend actuator with spatial thermal pattern

1. A thermal actuator for a micro-electromechanical device comprising:

(a) a base element;

(b) a cantilevered element including a thermo-mechanical bender portion extending from the base element and a free end tip residing in a first position, the thermo-mechanical bender portion having a base end adjacent the base element and a free end adjacent the free end tip; and

(c) apparatus adapted to apply a heat pulse having a spatial thermal pattern directly to the thermo-mechanical bender portion, causing the deflection of the free end tip of the cantilevered element to a second position, and wherein said spatial thermal pattern results in a substantially greater temperature increase of the base end than the free end of the thermo-mechanical bender portion.

2. The thermal actuator of claim 1 wherein the apparatus adapted to apply a heat pulse comprises a patterned thin film resistor layer.

3. The thermal actuator of claim 2 wherein the spatial thermal pattern results in part from spatially modifying the conductivity of the thin film resistor layer.

4. The thermal actuator of claim 1 wherein the thermo-mechanical bender portion includes a first deflector layer constructed of a first material having a high coefficient of thermal expansion and a second layer, attached to the first deflector layer, constructed of a second material having a low coefficient of thermal expansion.

5. The thermal actuator of claim 4 wherein the first material is electrically resistive having a first sheet resistance and the apparatus adapted to apply a heat pulse comprises a resistor pattern formed in the first deflector layer.

6. A liquid drop emitter comprising:

(a) a chamber, formed in a substrate, filled with a liquid and having a nozzle for emitting drops of the liquid;

(b) a thermal actuator having a cantilevered element including a thermo-mechanical bender portion extending from a wall of the chamber and a free end tip residing in a first position proximate to the nozzle, the thermo-mechanical bender portion having a base end adjacent the base element and a free end adjacent the free end tip; and

(c) apparatus adapted to apply a heat pulse having a spatial thermal pattern directly to the thermo-mechanical bender portion causing a rapid deflection of the free end tip and ejection of a liquid drop, and wherein said spatial thermal pattern results in a substantially greater temperature increase of the base end than the free end of the thermo-mechanical bending portion.

7. The liquid drop emitter of claim 6 wherein the liquid drop emitter is a drop-on-demand ink jet printhead and the liquid is ink for printing image data.

8. The liquid drop emitter of claim 6 wherein the apparatus adapted to apply a heat pulse comprises a patterned thin film resistor layer.

9. The liquid drop emitter of claim 8 wherein the spatial thermal pattern results in part from spatially modifying the conductivity of the thin film resistor layer.

10. The liquid drop emitter of claim 9 wherein the thermo-mechanical bender portion includes a first deflector layer constructed of a first material having a high coefficient of thermal expansion and a second layer, attached to the first deflector layer, constructed of a second material having a low coefficient of thermal expansion.

11. The liquid drop emitter of claim 10 wherein the first material is electrically resistive having a first sheet resistance and the apparatus adapted to apply a heat pulse comprises a resistor pattern formed in the first deflector layer.

12. A thermal actuator for a micro-electromechanical device comprising:

(a) a base element;

(b) a cantilevered element including a thermo-mechanical bender portion extending from the base element to a free end tip residing at a first position, the thermo-mechanical bender portion having a base end adjacent the base element and a free end adjacent the free end tip, the thermo-mechanical bender portion further including a first deflector layer constructed of a first material having a large coefficient of thermal expansion, a second deflector layer, and a barrier layer constructed of a dielectric material having low thermal conductivity wherein the barrier layer is bonded between the first deflector layer and the second deflector layer; and

(c) apparatus adapted to apply a heat pulse having a spatial thermal pattern directly to the first deflector layer, causing the deflection of the free end tip of the cantilevered element to a second position, followed by restoration of the cantilevered element to the first position as heat diffuses through the barrier layer to the second deflector layer and the cantilevered element reaches a uniform temperature, and wherein said spatial thermal pattern results in a substantially greater temperature increase of the base end than the free end of the first deflector layer.

13. The thermal actuator of claim 12 wherein the apparatus adapted to apply a heat pulse comprises a patterned thin film resistor layer.

14. The thermal actuator of claim 13 wherein the spatial thermal pattern results in part from spatially modifying the conductivity of the thin film resistor layer.

15. The thermal actuator of claim 14 wherein the first material is electrically resistive having a first sheet resistance and the apparatus adapted to apply a heat pulse comprises a resistor pattern formed in the first deflector layer.

16. The thermal actuator of claim 15 wherein the second deflector layer is constructed of the first material and the first deflector layer and the second deflector layer are substantially equal in thickness.

17. A liquid drop emitter comprising:

(a) a chamber, formed in a substrate, filled with a liquid and having a nozzle for emitting drops of the liquid;

(b) a cantilevered element including a thermo-mechanical bender portion extending from a wall of the chamber to a free end tip residing at a first position proximate to the nozzle, the thermo-mechanical bender portion having a base end adjacent the base element and a free end adjacent the free end tip, the thermo-mechanical bender portion further including a first deflector layer constructed of a first material having a large coefficient of thermal expansion, a second deflector layer, and a barrier layer constructed of a dielectric material having low thermal conductivity wherein the barrier layer is bonded between the first deflector layer and the second deflector layer; and

(c) apparatus adapted to apply a heat pulse having a spatial thermal pattern directly to the first deflector layer, causing a rapid deflection of the free end tip and ejection of a liquid drop, followed by restoration of the cantilevered element to the first position as heat diffuses through the barrier layer to the second deflector layer and the cantilevered element reaches a uniform temperature, and wherein said spatial thermal pattern results in a substantially greater temperature increase of the base end than the free end of the first deflector layer.

18. The liquid drop emitter of claim 17 wherein the apparatus adapted to apply a heat pulse comprises a patterned thin film resistor layer.

19. The liquid drop emitter of claim 18 wherein the spatial thermal pattern results in part from spatially modifying the conductivity of the thin film resistor layer.

20. The liquid drop emitter of claim 19 wherein the first material is electrically resistive having a first sheet resistance and the apparatus adapted to apply a heat pulse comprises a resistor pattern formed in the first deflector layer.

21. The liquid drop emitter of claim 17 wherein the second deflector layer is constructed of the first material and the first deflector layer and the second deflector layer are substantially equal in thickness.

22. The liquid drop emitter of claim 17 wherein the liquid drop emitter is a drop-on-demand ink jet printhead and the liquid is ink for printing image data.

23. A drop ejection device comprising:

a base;

a chamber for holding liquid to be ejected, the chamber formed on the base and having a nozzle opening;

a thermal bend actuator for ejecting drops of the liquid from the chamber through the nozzle, the bend actuator being configured as a cantilever with one end of the cantilever is anchored to the base and the opposite end supporting a liquid paddle, the actuator having a deflector section constructed of a material having a large coefficient of thermal expansion and a barrier layer constructed of a dielectric material having low thermal conductivity; wherein,

differential thermal expansion of the deflector section and the barrier layer causes the actuator to bend so that the paddle ejects drops of liquid from the nozzle.

24. The drop ejection device of claim 23 wherein the deflector section is configured for heating to provide a spatial thermal pattern along the cantilever such that the resultant temperature change is greater at the base end of the cantilever than the paddle end of the cantilever.

25. The drop ejection device of claim 24 wherein the deflector section is a first deflector layer and the device further comprises a second deflector layer, and the barrier layer is bonded between the first deflector layer and the second deflector layer such that the spatial heating pattern causes a substantially greater temperature increase of the base end than the free end of the first deflector layer.

26. The drop ejection device of claim 23 wherein the deflector section is a thin film resistor layer and the spatial thermal pattern results in part from spatially modifying the conductivity of the thin film resistor layer.

27. The drop ejection device of claim 26 wherein the second deflector layer is constructed of the same material as the first deflector layer and the second deflector layer is substantially equal in thickness to the first deflector layer.

28. The drop ejection device of claim 26 wherein the liquid drop emitter is a drop-on-demand ink jet printhead and the liquid is ink for printing image data.