Micro-electromechanical actuator that includes drive circuitry
View Patent ↗A micro-electromechanical actuator includes a substrate. Register, gate and drive transistor circuitry is positioned on the substrate. An elongate actuator arm is fast, at a first end, with the substrate. The elongate actuator arm includes a mechanical layer and a heater layer interposed between the mechanical layer and the substrate. The heater layer defines a heating circuit that expands and contracts longitudinally when heated and subsequently cooled, resulting in reciprocal movement of the actuator arm away from and towards the substrate. A working member is fast with a second end of the actuator. The register, gate and drive transistor circuitry are interposed between the heater layer and the substrate.
1. A micro-electromechanical actuator that comprises
a substrate;
register, gate and drive transistor circuitry positioned on the substrate;
an elongate actuator arm that is fast, at a first end, with the substrate, the elongate actuator arm comprising a mechanical layer and a heater layer interposed between the mechanical layer and the substrate, the heater layer defining a heating circuit that expands and contracts longitudinally when heated and subsequently cooled, resulting in reciprocal movement of the actuator arm away from and towards the substrate; and
a working member that is fast with a second end of the actuator, wherein
the register, gate and drive transistor circuitry are interposed between the heater layer and the substrate.
2. A micro-electromechanical actuator as claimed in claim 1 , in which a number of laterally extending traces define at least part of the drive transistor circuitry.
3. A micro-electromechanical actuator as claimed in claim 2 , in which the laterally extending traces are positioned on an upper poly layer formed on the substrate.
4. A micro-electromechanical actuator as claimed in claim 3 in which the working member is an ink-ejection member that is receivable in a nozzle chamber to eject ink from the nozzle chamber on reciprocal displacement of the actuator arm.
5. A micro-electromechanical actuator as claimed in claim 2 , in which the heater layer defines a series of laterally extending corrugations aligned generally with the laterally extending traces of the drive transistor circuitry.
6. A micro-electromechanical actuator as claimed in claim 1 , in which the working member is defined by a part of the heater layer, the heater layer further defining a discontinuity electrically to isolate the working member.
7. A micro-electromechanical actuator as claimed in claim 1 , in which the heater layer defines a pair of heater arms that are joined distally from the first end of the actuator arm and separated by a slot which tapers inwardly from the first end of the actuator arm.