Importance

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Abstract

An apparatus for and method of operating a thermal actuator for a micromechanical device, especially a liquid drop emitter such as an ink jet printhead, is disclosed. The disclosed thermal actuator comprises a base element and a cantilevered element extending a length L from a base element and normally residing at a first position before activation. The cantilevered element includes a barrier layer constructed of a dielectric material having low thermal conductivity, a first deflector layer constructed of a first electrically resistive material having a large coefficient of thermal expansion and patterned to have a first uniform resistor portion extending a length L.sub.H1 from the base element, wherein 0.3L.ltoreq.L.sub.H1.ltoreq.0.7L, and a second deflector layer constructed of a second electrically resistive material having a large coefficient of thermal expansion and patterned to have a second uniform resistor portion extending a length L.sub.H2 from the base element, wherein 0.3L.ltoreq.L.sub.H2.ltoreq.0.7L, and wherein the barrier layer is bonded between the first and second deflector layers. The thermal actuator further comprises a first pair of electrodes connected to the first uniform resistor portion and a second pair of electrodes is connected to the second uniform resistor portion for applying electrical pulses to cause resistive heating of the first or second deflector layers, resulting in thermal expansion of the first or second deflector layer relative to the other. Application of an electrical pulse to either pair of electrodes causes deflection of the cantilevered element away from its first position and, alternately, causes a positive or negative pressure in the liquid at the nozzle of a liquid drop emitter. Application of electrical pulses to the pairs of electrodes is used to adjust the characteristics of liquid drop emission. The barrier layer exhibits a heat transfer time constant .tau..sub.B. The thermal actuator is activated by a heat pulses of duration .tau..sub.P wherein .tau..sub.P <1/2 .tau..sub.B.

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First Claim