Thermal bend actuator and control circuitry for a micro-electromechanical device

• US 6,786,573 B2
• Filed: 11/17/2003
• Issued: 09/07/2004
• Est. Priority Date: 10/16/1998
• Status: Expired due to Fees

• Current Assignee: Memjet Technology Ltd. (Memjet Limited)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia
• Primary Examiner(s): Gordon, Raquel Yvette
• Application Number:
  US10/713,059
• Publication Number:
  US 20040095434A1
• Time in Patent Office: 295 Days
• Field of Search: 347/54, 347/68, 347/69, 347/70, 347/71, 347/72, 347/50, 347/40, 347/20, 347/44, 347/47, 347/27, 347/63, 399/261, 361/700, 310/328-330, 298/90
• US Class Current: 347/54
• CPC Class Codes: B05D 2201/00 Polymeric substrate or laminate
• CPC Class Codes: B05D 3/08 by flames
• CPC Class Codes: B41J 2/04528 aiming at warming up the head
• CPC Class Codes: B41J 2/04541 Specific driving circuit
• CPC Class Codes: B41J 2/04543 Block driving
• CPC Class Codes: B41J 2/04553 detecting ambient temperature
• CPC Class Codes: B41J 2/04563 detecting head temperature; Ink temperature
• CPC Class Codes: B41J 2/04571 detecting viscosity
• CPC Class Codes: B41J 2/04585 controlling heads based on thermal bent actuators
• CPC Class Codes: B41J 2/04588 using a specific waveform
• CPC Class Codes: B41J 2/04591 Width of the driving signal being adjusted
• CPC Class Codes: B41J 2/04596 Non-ejecting pulses
• CPC Class Codes: B41J 2/14 Structure thereof only for on-demand ink jet heads
• CPC Class Codes: B41J 2/14427 Structure of ink jet print heads with thermal bend detached actuators
• CPC Class Codes: B41J 2/1623 bonding and adhesion
• CPC Class Codes: B41J 2/1626 etching
• CPC Class Codes: B41J 2/1628 dry etching
• CPC Class Codes: B41J 2/1629 wet etching
• CPC Class Codes: B41J 2/1631 photolithography
• CPC Class Codes: B41J 2/1632 machining
• CPC Class Codes: B41J 2/1635 : dividing the wafer into individual chips
• CPC Class Codes: B41J 2/1639 : sacrificial molding
• CPC Class Codes: B41J 2/1642 : thin film formation by CVD [chemical vapor deposition]
• CPC Class Codes: B41J 2/1646 : thin film formation by sputtering
• CPC Class Codes: B41J 2/1648 : Production of print heads with thermal bend detached actuators
• CPC Class Codes: B41J 2002/14419 : Manifold
• CPC Class Codes: B41J 2002/14491 : Electrical connection
• CPC Class Codes: Y10T 29/49345 : Catalytic device making

Abstract

A thermal bend actuator includes a wafer substrate. An elongate actuator arm is fixed to the substrate at a fixed end. The elongate actuator arm includes a heater layer of a conductive material and a dielectric, resiliently flexible layer. The heater layer defines a heater circuit which is connected to an electrical potential. A working member is fixed to an opposite free end of the actuator arm. Control logic circuitry is positioned on the substrate, between, and generally aligned with, the heater layer and the substrate. The control logic circuitry is interconnected between a data input means and the heater circuit and includes register circuitry connected to the data input means to generate an enabling signal. Firing circuitry is connected between the register circuitry and the heater circuit to close the heater circuit on receipt of the enabling signal so that said electrical potential generates a current in the heater circuit, resistively to heat the heater layer. At least the heater layer is of a material that has a coefficient of thermal expansion which is such that the heater layer can expand on heating and contract on cooling to do work. The heater layer is positioned so that the elongate actuator arm experiences differential thermal expansion and contraction and thus reciprocally displaces the working member.

Claims

1. A thermal bend actuator which includes

a wafer substrate;

an elongate actuator arm that is fixed to the substrate at a fixed end, the elongate actuator arm including a heater layer of a conductive material and a dielectric, resiliently flexible layer, the heater layer defining a heater circuit which is connected to an electrical potential;

a working member that is fixed to an opposite free end of the actuator arm; and

control logic circuitry that is positioned on the substrate, between, and generally aligned with, the heater layer and the substrate, the control logic circuitry being interconnected between a data input means and the heater circuit and including register circuitry connected to the data input means to generate an enabling signal and firing circuitry connected between the register circuitry and the heater circuit to close the heater circuit on receipt of the enabling signal so that said electrical potential generates a current in the heater circuit, resistively to heat the heater layer, at least the heater layer being of a material having a coefficient of thermal expansion which is such that the heater layer can expand on heating and contract on cooling to do work, the heater layer being positioned so that the elongate actuator arm experiences differential thermal expansion and contraction and thus reciprocally displaces the working member.

2. A thermal bend actuator as claimed in claim 1, in which the control logic circuitry is configured so that traces defining the circuitry extend substantially at right angles with respect to a longitudinal axis of the actuator arm.

3. A thermal bend actuator as claimed in claim 2, in which the heater layer defines corrugations in regions that are aligned with the control circuitry, the corrugations extending substantially at right angles to the longitudinal axis of the actuator arm.

4. A thermal bend actuator as claimed in claim 1, in which the heater layer defines a transverse discontinuity such that a portion of the heater layer defines the heating circuit and is connected to the control logic circuitry and a remaining portion of the heater layer defines a structural supporting layer for the actuator arm.

5. A thermal bend actuator as claimed in claim 1, which includes a bend compensator layer that is positioned so that the dielectric layer is interposed between the heater layer and the bend compensator layer, the bend compensator layer being substantially identical to the heater layer.

6. A micro-electromechanical device that comprises

a substrate;

and

a plurality of thermal bend actuators that are positioned on the substrate, each thermal bend actuator comprising

an elongate actuator arm that is fixed to the substrate at a fixed end, the elongate actuator arm including a heater layer of a conductive material and a dielectric, resiliently flexible layer, the heater layer defining a heater circuit which is connected to an electrical potential;

a working member that is fixed to an opposite free end of the actuator arm; and

control logic circuitry that is positioned on the substrate between, and generally aligned with, the heater layer and the substrate, the control logic circuitry being interconnected between a data input means and each heater circuit and including register circuitry connected to the data input means to generate an enabling signal and firing circuitry connected between the register circuitry and the heater circuit to close the heater circuit on receipt of the enabling signal so that said electrical potential generates a current in the heater circuit, resistively to heat the heater layer, at least the heater layer being of a material having a coefficient of thermal expansion which is such that the heater layer can expand on heating and contract on cooling to do work, the heater layer being positioned so that the elongate actuator arm experiences differential thermal expansion and contraction and thus reciprocally displaces the working member.