MEMS-based actuator devices using electrets

• US 7,177,505 B2
• Filed: 03/04/2004
• Issued: 02/13/2007
• Est. Priority Date: 03/04/2004
• Status: Expired due to Fees

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Willcox, Charles R.
• Primary Examiner(s): Healy; Brian
• Assistant Examiner(s): PENG, CHARLIE YU
• Application Number:
  US10/792,982
• Publication Number:
  US 20050196099A1
• Time in Patent Office: 1,076 Days
• Field of Search: 385/140, 385/73, 385/52, 385/16, 385/23, 385/25
• US Class Current: 385/52
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/3508 Lateral or transverse displacement of the whole waveguides, e.g. by varying the distance between opposed waveguide ends, or by mutual lateral displacement of opposed waveguide ends
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G02B 6/3594 Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams

Abstract

Electrets are used in a variety of MEMS-based actuator devices. The electret is able to store electrical charge for a long time with negligible charge leakage. Therefore, when an electret is incorporated into a MEMS device that requires actuation, the device can be initially biased to any desired actuation state for a long period of time without the use of external bias voltages. Such a MEMS-based device may include a MEMS-based actuator having at least a first deflectable member and at least a second member. The first deflectable member and the second member are provided with a floating electrode and a second electrode. A charge on the first floating electrode is selected so as to position the first deflectable member at a desired separation distance from the second member. The device may be used to align an optical component or to change the electrical characteristics of an electrical element.

Claims

1. A MEMS-based optical device, comprising:

a MEMS-based actuator having at least a first deflectable member and at least a second member, at least a first floating electrode disposed on one of the first deflectable member and the second member, the other of the first deflectable member and the second member being provided with a second electrode, a charge on the first floating electrode being selected so as to position the deflectable member at a desired separation distance from the second member;

one of the deflectable member and the second member comprising a first optical element;

a bias position of the first optical element relative to a second optical element being determined, at least in part, by the position of the deflectable member.

2. A device as recited in claim 1, wherein the deflectable member comprises the first optical element.

3. A device as recited in claim 1, wherein the deflectable member is a first optical fiber having a first end.

4. A device as recited in claim 3, wherein the second optical element is a second optical fiber having a second end opposing the first end of the first optical fiber, a position of the first optical fiber transverse to the second optical fiber being determined, at least in part, by the charge on the first floating electrode.

5. A device as recited in claim 4, wherein the first optical fiber comprises a first grounded electrode and the second member comprises a frame having the first floating electrode and at least a second floating electrode, electrical charges on at least the first and second floating electrodes determining a position of the first optical fiber relative to the frame.

6. A device as recited in claim 5, wherein the second optical fiber comprises a second grounded electrode, and the frame comprises at least third and fourth floating electrodes, electrical charges on the third and fourth floating electrodes determining a position of the second optical fiber relative to the frame.

7. A device as recited in claim 5, further comprising a tunable electrode on the frame, and electric charge stored on the tunable electrode also determining, at least in part, the position of the first optical element relative to the second optical element.

8. A device as recited in claim 1, wherein the deflectable member comprises a holographic optical element (HOE).

9. A device as recited in claim 8, wherein the second member comprises a frame, the floating electrode being provided on the frame and the HOE comprising a grounded electrode.

10. A device as recited in claim 8, wherein the second optical element is an optically transparent substrate with first and second surfaces, light totally internally reflecting within the optically transparent substrate at the first and second surfaces.

11. A device as recited in claim 10, further comprising a tunable electrode, wherein a bias position of the HOE is determined by the charge stored on the floating electrode when there is no charge on the tunable electrode, the HOE moving to a switched position when there is charge on the tunable electrode.

12. A device as recited in claim 1, wherein the device comprises a tunable Fabry Perot filter formed by two optically reflecting surfaces, at least one of the optically reflecting surfaces being disposed on an aligning member for alignment relative to the other reflecting surface so as to form a Fabry-Perot resonator therewith, the aligning member comprising the deflectable member, with at least one of the optically reflecting surfaces disposed on the aligning member comprising the first optical element.

13. A device as recited in claim 12, wherein at least one of the two optically reflecting surfaces comprises an end of an optical fiber.

14. A device as recited in claim 12, further comprising a flexible member, one of the optically reflecting surfaces being mounted so as to be movable along a filter axis when the flexible member flexes, so as to change a separation distance between the optically reflecting surfaces.

15. A device as recited in claim 1, wherein the deflectable member comprises a mirror.

16. A device as recited in claim 1, further comprising a hot electron injector provided to inject electrons to the first floating electrode.

17. A device as recited in claim 1, wherein the optical device is formed, at least in part, from silicon.

18. A device as recited in claim 1, wherein the optical device is formed, at least in part, from quartz.

19. A device as recited in claim 1, wherein the optical device is formed, at least in part, from sapphire.

20. A MEMS-based electrical device, comprising:

a MEMS-based actuator having at least a first deflectable member and at least a second member, at least a first floating electrode disposed on one of the first deflectable member and the second member, the other of the first deflectable member and the second member being provided with a second electrode, a charge on the first floating electrode being selected so as to position the deflectable member at a desired separation distance from the second member;

at least one of the deflectable member and the second member comprising an electrical element having an electrical characteristic dependent on a position of the first deflectable member relative to the second member.

21. A device as recited in claim 20, wherein the electrical element is a strain-sensitive resistor, a value of resistance of the strain-sensitive resistor being dependent on the position of the first deflectable member relative to the second member.

22. A device as recited in claim 20, wherein the electrical element is a capacitor comprising first and second capacitor electrodes, one of the first and second capacitor electrodes being provided on the first deflectable member so that a value of capacitance of the capacitor is dependent on the position of the first deflectable member relative to the second member.

23. A device as recited in claim 22, wherein the floating electrode is provided on the second member and the first deflectable member is provided with a grounded electrode.

24. A device as recited in claim 23, wherein the grounded electrode comprises one of the first and second capacitor electrodes provided on the first deflectable member.

25. A device as recited in claim 24, wherein the other of the first and second capacitor electrodes is provided on the second member.

26. A device as recited in claim 20, further comprising a hot electron injector provided to inject electrons to the first floating electrode.

27. A device as recited in claim 20, wherein the electrical device is formed, at least in part, from silicon.

28. A device as recited in claim 20, wherein the electrical device is formed, at least in part, from quartz.

29. A device as recited in claim 20, wherein the electrical device is formed, at least in part, from sapphire.

30. A MEMS-based device, comprising:

a MEMS-based actuator having at least a first deflectable member and at least a second member, at least a first floating electrode disposed on one of the first deflectable member and the second member the other of the first deflectable member and the at least a second member being provided with a second electrode, a charge on the first floating electrode being selected so as to position the first deflectable member at a desired separation distance from the second member.

31. A device as recited in claim 30, wherein the second electrode is a grounded electrode.

32. A device as recited in claim 30, wherein the second electrode is a second floating electrode.

33. A device as recited in claim 30, wherein the second member is deflectable.

34. A device as recited in claim 30, further comprising a hot electron injector provided to inject electrons to the first floating electrode.

35. A device as recited in claim 30, further comprising a second floating electrode disposed on the other of the first deflectable member and the second member, wherein charges on the first and second floating electrodes are selected to as to position the first deflectable member at the desired separation distance from the second member.

36. A device as recited in claim 30, wherein the device is formed, at least in part, from silicon.

37. A device as recited in claim 30, wherein the device is formed, at least in part, from quartz.

38. A device as recited in claim 30, wherein the device is formed, at least in part, from sapphire.