Thermal actuator with reduced temperature extreme and method of operating same

摘要

An apparatus for a thermal actuator (15) for a micromechanical device, especially a liquid drop emitter (110) such as an ink jet printhead, is disclosed. The disclosed thermal actuator comprises a base element (10) and a cantilevered element (20) extending from the base element and normally residing at a first position before activation. The cantilevered element includes a first layer (22) constructed of an electrically resistive material, such as titanium aluminide, patterned to have a first resistor segment (62) and a second resistor segment (64) each extending from the base element; a coupling device (68) that conducts electrical current serially between the first and second resistor segments; and a second layer (23) constructed of a dielectric material having a low coefficient of thermal expansion and attached to the first layer. A first electrode (42) connected to the first resistor segment and a second electrode (44) connected to the second resistor segment are provided to apply an electrical voltage pulse between the first and second electrodes thereby causing an activation power density in the first and second resistor segments and a power density maximum within the coupling device resulting in a deflection of the cantilevered element to a second position and wherein the power density maximum is less than four times the activation power density. The coupling device may be formed as a segment in the first layer or in a third layer of an electrically active material. Methods of operating a liquid drop emitter having a thermal actuator are disclosed which avoid the generation of vapor bubbles.