Tilting Actuator with Close-Gap Electrodes

• US 20100006958A1
• Filed: 06/15/2009
• Published: 01/14/2010
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: Ramot at Tel Aviv University Limited (Tel Aviv University)
• Original Assignee: Ramot at Tel Aviv University Limited (Tel Aviv University)
• Inventors: Shmilovich, Tsvi, Krylov, Slava
• Granted Patent: US 8,378,434 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• 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: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type

Abstract

An electromechanical tilting device including a first and a second electrode structures, shaped, positioned and oriented to define at least partially interdigitated electrodes, and a suspension defining a tilt-containing motion path for the second structure with respect to the first structure. The motion path is selected to cause changes in overlapping regions and overlapping regions'"'"' gaps of the interdigitated electrodes. The device is configured such that an increase in one or more voltage bias applied to interdigitated driving electrodes makes a decrease in a total area of overlapping regions of the driving electrodes electrically energetically favorable.

Claims

1. An electromechanical tilting device comprising a first and a second electrode structures, shaped, positioned and oriented to define at least partially interdigitated electrodes, and a suspension configured to define a tilt-containing motion path for the second electrode structure with respect to the first electrode structure, said motion path being configured to cause changes in overlapping regions and overlapping regions'"'"' gaps of the interdigitated electrodes along the motion path, such that an increase in one or more voltage bias applied to interdigitated driving electrodes affects vertical comb and closed gap forces applied to said first and second electrode structures.

2. The device of claim 1, said interdigitated electrodes having a common material layer.

3. The device of claim 1, said tilt-containing motion path comprising a rotation about a rotation axis substantially parallel to the electrodes of the electrode structure.

4. The device of claim 1, connectable to one or more voltage source adapted to provide said bias by providing at least one of the following:

an ac voltage a dc voltage and a sum of dc and ac voltages, the device thereby being usable as an actuator.

9. The device of claim 1, the suspension has at least one of the following configurations:

comprises a torsion axis;

comprises a bending flexure;

is electrically conductive.

10. The device of claim 1, wherein the suspension comprises a torsion axis having a common material layer with said interdigitated electrodes.

11. The device of claim 10, the common material layer being thinner in a region of the torsion axis than within electrodes of the second structure.

12. The device of claim 1, the suspension comprising a torsion axis being offset from an interdigitation axial center line of the second electrode structure.

15. The device of claim 1, the device being configured to have an equilibrium while said one or more voltage bias is zero and the electrodes of the first and second electrode structures are in at least on of the following configurations:

(i) substantially parallel to each other;

(ii) overlap for more than one half of their area;

(iii) overlap for more than two thirds of their area.

19. The device of claim 1, the electrodes having a rectangular shape in at least one cross-section.

22. The device of claim 1, comprising a silicon layer, said silicon layer being either a common material layer of said interdigitated electrodes or the layer of the second electrode structure.

24. The device of claim 1, wherein at least one of said electrode structures is in the form of a comb structure and wherein at least two of the electrodes of the comb structure are connected to different voltage sources.

25. The device of claim 1, the motion path of the second electrode structure being geometrically limited by the first electrode structure.

26. The device of claim 1, comprising a layer of a silicon-on-insulator (SOI) wafer.

27. The device of claim 1, having an optically reflective region tilting in the course of the motion of the second structure, the region thereby being capable of serving as a scanning mirror.

28. A gyroscope comprising the device of claim 1.

29. The device of claim 1, fabricated as a MEMS device.

30. The device of claim 1, configured to have three stable states of equilibrium with no contact between the first and the second electrode structures or contact between the electrode structures and a mechanical constraining structure.

32. The device of claim 1, configured to have, for the electrodes biased with a constant voltage, at least two positions of electrical equilibrium within said motion path.

35. The device of claim 32, wherein each of said first and second electrode structures defines at least one electrode.

47. The device of claim 1, being configured to define the motion path having at least a portion thereof, within which one or more voltage bias applied to the interdigitated driving electrodes causes a decrease in a total area of the overlapping regions of the driving electrodes electrically energetically favorable.

48. The device of claim 47 comprising an excitation unit configured to excite the device at a parametric resonance frequency.

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36. An electromechanical tilting device comprising a first and a second electrode structures and a suspension defining a motion path for the second structure with respect to the first structure, at least one of the structures comprising two electrically isolated electrodes, the device being configured to have in at least a portion of said motion path an electrically energetically favorable direction of motion being dependent on selection of whichever one of said two electrically isolated electrodes is biased.

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39. A tunable tilting device comprising a holding element, a tilting element and a suspension structure coupling said elements and defining a tilt-containing motion path for the tilting element with respect to the holding element, the tilting element being substantially responsive to an actuating field of a type acting to cause a motion of the element along said motion path, the suspension structure being configured to bend with a certain bending stiffness to provide the tilting element said motion path, said suspension structure being substantially responsive to a tuning field which is of a type acting to change an extension stress of the structure and thereby to change the bending stiffness of the suspension structure.

40. The device of claim 39 fabricated as a MEMS device.

41. The device of claim 39 comprising a mirror carried by the tilting element.

42. The device of claim 39, the tilt-containing motion path comprising a rotation around a virtual axis.

43. The device of claim 39, wherein at least one of the actuation field and the tuning field is electrostatic.

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