Rotational Type of MEMS Electrostatic Actuator

• US 20130194649A1
• Filed: 01/25/2013
• Published: 08/01/2013
• Est. Priority Date: 01/26/2012
• Status: Active Grant

• Current Assignee: Preciseley Microtechnology Corporation
• Original Assignee: Tiansheng Zhou
• Inventors: Zhou, Tiansheng
• Granted Patent: US 9,385,634 B2
• Time in Patent Office: Days
• US Class Current: 359/230
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/023 comprising movable attenuating elements, e.g. neutral density filters
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 7/06 having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors electrets H01G7/02
• CPC Class Codes: H02N 1/002 Electrostatic motors

Abstract

A cantilever type of electrostatic vertical combdrive actuators may generate larger actuator displacement (typically over 70 um) with a relatively small and simple structure. The actuation voltage is lower while the actuation movement is robust without any typical sideway finger snapping phenomena due to a cantilever type of structure. Because of its small form factor, it can form a high fill factor array in applications such as lower power consumption display devices, sensitive electromagnetic radiation detector/detector arrays, etc. The MEMS (Micro-Electro-Mechanical Systems) electrostatic rotational actuators may have wide applications such as in optical shutter, optical chopper, optical switches, optical attenuators, optical tunable filter, RF shunt switch, RF ohmic contact switch, RF MEMS variable capacitors, MEMS display and sensitive electromagnetic radiation detector etc.

Claims

1. A MEMS actuator, comprising:

a combdrive carried by a substrate, the combdrive having a fixed comb and a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate;

a resilient body attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb in response to an actuating voltage applied to the combdrive, the comb fingers of the fixed and movable combs being curved in the direction of the movement.

2. The MEMS actuator of claim 1, wherein the fixed comb and the movable comb are electrically isolated.

3. The MEMS actuator of claim 2, wherein the movable comb moves toward the fixed comb in response to the actuating voltage.

4. The MEMS actuator of claim 1, wherein the movable comb is attached to the resilient body by a carrier body.

5. The MEMS actuator of claim 1, wherein the combdrive comprises a plurality of movable combs and fixed combs.

6. The MEMS actuator of claim 5, comprising movable combs on opposed sides of a carrier body attached to the resilient body, the opposed movable combs permitting pivotal movement of the movable combs selectively in opposed directions.

7. The MEMS actuator of claim 5, comprising movable combs on the same side of a carrier body attached to the resilient body.

8. The MEMS actuator of claim 1, further comprising at least one contact point on the substrate and the movable comb carries an electrically conductive connector, the movement of the movable comb controlling the connection of the at least one contact point and the connector.

9. The MEMS actuator of claim 8, comprising more than one contact point, and the connector acting as a switch between the contact points.

10. The MEMS actuator of claim 8, wherein the connector is mounted toward the anchor point relative to the movable comb.

11. The MEMS actuator of claim 8, wherein the connector is electrically isolated from the movable comb and the resilient body.

12. The MEMS actuator of claim 1, wherein the movable comb carries a shutter, the shutter preventing transmission of some or all wavelengths in a beam of light, the movable comb controlling the position of the shutter within the beam of light.

13. The MEMS actuator of claim 12, wherein the shutter comprises a profiled edge.

14. The MEMS actuator of claim 12, wherein the shutter is attached at an end of the movable comb.

15. The MEMS actuator of claim 12, wherein the shutter is mounted across at least a portion of the comb fingers of the movable comb.

16. The MEMS actuator of claim 12, wherein the substrate comprises an aperture, the beam of light passing through the aperture.

17. The MEMS actuator of claim 1, wherein the resilient body comprises a beam structure.

18. The MEMS actuator of claim 1, wherein the resilient body comprises a double beam structure.

19. The MEMS actuator of claim 18, wherein each beam is electrically isolated from the other and electrically connected to separate anchor points to form a circuit through the resilient body between the anchor points.

20. The MEMS actuator of claim 19, wherein the circuit is connected to a filament carried by the movable comb.

21. The MEMS actuator of claim 1, further comprising a counterweight opposite the movable comb relative to the anchor point.

22. The MEMS actuator of claim 21, wherein the counterweight comprises one or more movable combs.

23. The MEMS actuator of claim 1, wherein the spacing of the comb fingers of the movable comb within the comb fingers of the fixed comb is scaled to balance the applied electrostatic forces as the movable comb moves.

24. The MEMS actuator of claim 1, wherein the curvature of the fingers follows the trajectory of the movable comb when an electrostatic force is applied.

25. The MEMS actuator of claim 1, wherein the resilient body supports the movable comb in a cantilever design.

26. The MEMS actuator of claim 1, wherein the resilient body comprises a first part attached between a first anchor and a first side of the movable comb and a second part attached between a second anchor and a second side of the movable comb, such that the movable comb is supported by the resilient body between the first anchor and the second anchor.

27. The MEMS actuator of claim 26, wherein each of the first and second parts of the resilient body comprises a pair of beams, the beams being one of parallel or converging toward the movable comb from the respective anchor.

28. The MEMS actuator of claim 26, wherein the first part and the second part are symmetrical about the movable comb.

29. A variable capacitor, comprising:

a combdrive carried by a substrate, the combdrive having a first electrode comprising a fixed comb and a second electrode comprising a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate;

a resilient body attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb, wherein an actuating voltage moves the movable comb relative to the fixed comb, the comb fingers of the fixed and movable combs being curved in the direction of the movement the combdrive having a capacitance that increases as the overlap of the comb fingers of the fixed comb and the movable comb increases.

30. The variable capacitor of claim 29, wherein, in a disengaged position, the combdrive comprises a space between the comb fingers of the movable comb and the comb fingers of the fixed comb.

31. The variable capacitor of claim 29, wherein the combdrive comprises a first combdrive, and further comprising a second combdrive that rotates the resilient body in a direction opposite the first combdrive.

32. The variable capacitor of claim 29, wherein the combdrive comprises a first combdrive, and further comprising at least one second combdrive that rotates the resilient body in the same direction as the first combdrive.

33. The variable capacitor of claim 29 connected in series or in parallel with a plurality of variable capacitors mounted to a common substrate.

34. The variable capacitor of claim 29, wherein the position of the movable comb and the capacitance of the combdrive is related to the actuating voltage applied to the combdrive.

35. An array of MEMS actuators mounted to a substrate, each MEMS actuator comprising:

a combdrive carried by a substrate, the combdrive having a fixed comb and a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate;

a resilient body attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb in response to an actuating voltage, the comb fingers of the fixed and movable combs being curved in the direction of the movement.

36. The array of MEMS actuators of claim 35, wherein the substrate comprises apertures for beams of light, the movable combs carrying shutters that control passage of light through the apertures.

37. The array of MEMS actuators of claim 36, wherein the substrate is a waveguide plate.

38. The array of MEMS actuators of claim 37, wherein the actuating voltage comprises a periodic voltage having a frequency.