Tapered multi-layer thermal actuator and method of operating same

A method for operating a thermal actuator, said thermal actuator comprising a base element;

• 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 including the cantilevered element including a barrier layer having a heat transfer time constant τB, 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 a second deflector layer constructed of a second electrically resistive material having a large coefficient of thermal expansion wherein the barrier layer is bonded between the first and second deflector layers;
• the thermo-mechanical bender portion further having a base end and base end width, wb, adjacent the base element, and a free end and free end width, wf, adjacent the free end tip, wherein the base end width is substantially greater than the free end width;
• a first heater resistor formed in the first deflector layer and adapted to apply heat energy having a first spatial thermal pattern which results in a first deflector layer base end temperature increase, ΔT1b, in the first deflector layer at the base end that is greater than a first deflector layer free end temperature increase, ΔT1f, in the first deflector layer at the free end;
• a second heater resistor formed in the second deflector layer and adapted to apply heat energy having a second spatial thermal pattern which results in a second deflector layer base end temperature increase, ΔT2b, in the second deflector layer at the base end that is greater than a second deflector layer free end temperature increase, ΔT2f, in the second deflector layer at the free end;
• a first pair of electrodes connected to the first heater resistor to apply an electrical pulse to cause resistive heating of the first deflector layer, resulting in a thermal expansion of the first deflector layer relative to the second deflector layer;
• a second pair of electrodes connected to the second heater resistor portion to apply an electrical pulse to cause resistive heating of the second deflector layer, the method for operating comprising:
• (a) applying to the first pair of electrodes a first electrical pulse which provides sufficient heat energy to cause a first deflection of the cantilevered element;
• (b) waiting for a time τW1;
• and
• (c) applying to the second pair of electrodes a second electrical pulse which provides sufficient heat energy to cause a second deflection of the cantilevered element;
• wherein the time τW1 is selected to achieve a predetermined resultant of the first and second deflections.

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 including 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 a second deflector layer constructed of a second electrically resistive material having a large coefficient of thermal expansion wherein the bamer layer is bonded between the first and second deflector layers;
• the thermo-mechanical bender portion further having a base end and base end width, wb, adjacent the base element, and a free end and free end width, wf, adjacent the free end tip, wherein the base end width is substantially greater than the free end width;
• (c) a first heater resistor formed in the first deflector layer and adapted to apply heat energy having a first spatial thermal pattern which results in a first deflector layer base end temperature increase, ΔT1b, in the first deflector layer at the base end that is greater than a first deflector layer free end temperature increase, ΔT1f, in the first deflector layer at the free end;
• (d) a second heater resistor formed in the second deflector layer and adapted to apply heat energy having a second spatial thermal pattern which results in a second deflector layer base end temperature increase, ΔT2b, in the second deflector layer at the base end that is greater than a second deflector layer free end temperature increase, ΔT2f, in the second deflector layer at the free end;
• (e) a first pair of electrodes connected to the first heater resistor to apply an electrical pulse to cause resistive heating of the first deflector layer, resulting in a thermal expansion of the first deflector layer relative to the second deflector layer;
• and
• (f) a second pair of electrodes connected to the second heater resistor portion to apply an electrical pulse to cause resistive heating of the second deflector layer, resulting in a thermal expansion of the second deflector layer relative to the first deflector layer, wherein application of electrical pulses to the first and second pairs of electrodes causes rapid deflection of the cantilevered element, ejecting liquid at the nozzle, followed by restoration of the cantilevered element to the first position as heat diffuses through the barrier layer and the cantilevered element reaches a uniform temperature.

A method for operating a liquid drop emitter, said liquid drop emitter comprising a chamber, formed in a substrate, filled with a liquid and having a nozzle for emitting drops of the liquid;

• 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-comprising a base element;
• 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 including the cantilevered element including a barrier layer having a heat transfer time constant τB, 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 a second deflector layer constructed of a second electrically resistive material having a large coefficient of thermal expansion wherein the barrier layer is bonded between the first and second deflector layers;
• the thermo-mechanical bender portion further having a base end and base end width, wb, adjacent the base element, and a free end and free end width, wf, adjacent the free end tip, wherein the base end width is substantially greater than the free end width;
• a first heater resistor formed in the first deflector layer and adapted to apply heat energy having a first spatial thermal pattern which results in a first deflector layer base end temperature increase, ΔT1b, in the first deflector layer at the base end that is greater than a first deflector layer free end temperature increase, ΔT1f, in the first deflector layer at the free end;
• a second heater resistor formed in the second deflector layer and adapted to apply heat energy having a second spatial thermal pattern which results in a second deflector layer base end temperature increase, ΔT2b, in the second deflector layer at the base end that is greater than a second deflector layer free end temperature increase, ΔT2f, in the second deflector layer at the free end;
• a first pair of electrodes connected to the first heater resistor to apply an electrical pulse to cause resistive heating of the first deflector layer, resulting in a thermal expansion of the first deflector layer relative to the second deflector layer;
• a second pair of electrodes connected to the second heater resistor portion to apply an electrical pulse to cause resistive heating of the second deflector layer, the method for operating comprising:
• (a) applying to the first pair of electrodes a first electrical pulse which provides sufficient heat energy to cause a first deflection of the cantilevered element;
• (b) waiting for a time τW1;
• and
• (c) applying to the second pair of electrodes a second electrical pulse which provides sufficient heat energy to cause a second deflection of the cantilevered element;
• wherein the time τW1 is selected to achieve a predetermined motion of the thermal actuator resulting in liquid drop emission.