Thermal actuator with optimized heater length

A thermal actuator for a micro-electromechanical device comprising:

• (a) a base element;
• (b) a cantilevered element extending a length L from the base element and residing at a first position, the cantilevered element including a first layer constructed of titanium aluminide which extends substantially the length L of the cantilevered element and is patterned to have a uniform resistor portion extending a length LH from the base element, wherein 0.3L≦LH≦0.7L, and a second layer constructed of a dielectric material having a low coefficient of thermal expansion and attached to the first layer;
• and
• (c) a pair of electrodes connected to the uniform resistor portion to apply an electrical pulse to cause resistive heating, resulting in a thermal expansion of the uniform resistor portion of the first layer relative to the second layer and deflection of the cantilevered element to a second position, followed by restoration of the cantilevered element to the first position as heat transfers from the uniform resistor portion and the temperature thereof decreases.

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 extending a length L from a wall of the chamber and a free end residing in a first position proximate to the nozzle, the cantilevered element including a first layer constructed of an electrically resistive material patterned to have a uniform resistor portion extending a length LH from the wall of the chamber, wherein 0.3L ≦LH<0.7L, and a second layer constructed of a dielectric material having a low coefficient of thermal expansion and attached to the first layer;
• and
• (c) a pair of electrodes connected to the uniform resistor portion to apply an electrical pulse to cause resistive heating, resulting in a thermal expansion of the uniform resistor portion of the first layer relative to the second layer and rapid deflection of the cantilevered element, ejecting liquid at the nozzle, followed by restoration of the cantilevered element to the first position as heat transfers from the uniform resistor portion and the temperature thereof decreases.

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 extending a length L from a wall of the chamber and a free end residing in a first position proximate to the nozzle, the cantilevered element including a first layer constructed of titanium aluminide which extends substantially the length L of the cantilevered element and is patterned to have a uniform resistor portion extending a length LH from the wall of the chamber, wherein 3.0L≦LH≦0.7L, and a second layer constructed of a dielectric material having a low coefficient of thermal expansion and attached to the first layer;
• and
• (c) a pair of electrodes connected to the uniform resistor portion to apply an electrical pulse to cause resistive heating, resulting in a thermal expansion of the uniform resistor portion of the first layer relative to the second layer and rapid deflection of the cantilevered element, ejecting liquid at the nozzle, followed by restoration of the cantilevered element to the first position as heat transfers from the uniform resistor portion and the temperature thereof decreases.