MEMS devices exhibiting linear characteristics

• US 8,966,990 B2
• Filed: 02/10/2012
• Issued: 03/03/2015
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Indiana University, Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Clark, Jason Vaughn
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US13/371,024
• Publication Number:
  US 20120204643A1
• Time in Patent Office: 1,117 Days
• Field of Search: 737/18, 737/24, 735/143.2, 361/283.1, 361/283.4
• US Class Current: 73/724
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

A micro electro mechanical system device has a first subassembly having sensor element including a coupler, and a second subassembly including a comb drive. The comb drive having stator plates and rotor plates and the coupler configured to displace the rotor plates relative to the stator plates providing a variable capacitance dependent on the displacement of the rotor plate.

Claims

1. A microfabricated variable capacitor, comprising:

a stationary stator portion including a plurality of electrically conductive plates each spaced apart from one another, each said pair of adjacent plates forming a channel therebetween, each of said plates being in a first common electrical communication;

a movable rotor portion including a plurality of electrically conductive blades each of said plurality of blades being in a second common electrical communication;

a stub in contact with the movable rotor portion; and

wherein said movable rotor portion is suspended relative to said stationary stator portion by flexible support portions that bias each of said blades vertically within a corresponding one of said channels, the stub displaces the movable rotor portion relative to the stationary stator portion against the bias of the flexible support portion, a portion of each said blade coacts with an adjacent said plate to store electrical charge, and the capacitance between the first electrical communication and the second electrical communication varies as said blades are displaced in a vertical direction.

2. The capacitor of claim 1, wherein said stub is configured to couple to an object.

3. The capacitor of claim 2 wherein said stub displaces said moving rotor portion dependent upon movement of said object.

4. The capacitor of claim 1 further comprising a flexible object having a first portion coupled to said stationary stator portion and a second portion coupled to said movable rotor portion, wherein said first portion is movable relative to said second portion.

5. The capacitor of claim 1, wherein said flexible support portions includes a first cantilever support extending from one end of said stator to said rotor and a second cantilever support extending from the opposite end of said stator to said rotor.

6. The capacitor of claim 5, wherein said first cantilever support is fixed at the one end and said second cantilever support is fixed at the opposite end.

7. The capacitor of claim 1, wherein said rotor includes a centrally located hub, and said blades are cantileveredly supported from said hub.

8. The capacitor of claim 7 which further comprises a cantilever arm supporting said blades, one end of said arm being coupled to said hub, each said blade extending from said arm in a direction that is generally transverse to the direction from the hub to the free end of said arm.

9. The capacitor of claim 1, wherein said plates are planar and said blades are planar.

10. The capacitor of claim 1, wherein said plates are circular about an axis and said blades are circular about the same axis.

11. The capacitor of claim 1 wherein said flexible support portion has a first spring constant corresponding to movement of said blades parallel to said plates, and a second spring constant corresponding to movement of said blades toward said plates, and the second spring constant is greater than the first spring constant.

12. A micro electro mechanical system sensor, comprising:

a comb drive having a stator portion with a plurality of stator plates each spaced apart from one another and a rotor portion including a plurality of rotor plates spaced apart from one another, the rotor portion being elastically suspended from said stator portion, the plurality of stator plates and the plurality of rotor plates forming a capacitor having a capacitance that varies with the vertical position of the rotor portion relative to the stator portion;

a membrane suspended proximate the comb drive, the membrane having a stub in physical contact with the rotor portion of the comb drive, the stub biasing the rotor portion to a first position having a first comb drive capacitance; and

wherein a movement of the membrane causes the stub to bias the rotor portion to a second position having a second comb capacitance.

13. The micro electro mechanical system sensor of claim 12 wherein the stator plates and the rotor plates are parallel.

14. The micro electro mechanical system sensor of claim 12 further comprising a packaging defining a pressure port and an otherwise fluid impervious environment.

15. The micro electro mechanical system sensor of claim 12 wherein the stator plates and the rotor plates are arcuate elements positioned at spaced distances from a common center.

16. The micro electro mechanical system sensor of claim 15 wherein the stub contacts the common center.

17. The capacitor of claim 12, wherein said rotor portion is elastically suspended from said stator portion by a first cantilever support extending from one end of said stator to said rotor and a second cantilever support extending from the opposite end of said stator to said rotor.

18. The capacitor of claim 17, wherein said first cantilever support is fixed at the one end and said second cantilever support is fixed at the opposite end.

19. The capacitor of claim 12, wherein said rotor portion includes a centrally located hub, and said rotor plates are cantileveredly supported from said hub.

20. The capacitor of claim 19 which further comprises a cantilever arm supporting said rotor plates, one end of said arm being coupled to said hub, each said rotor plate extending from said arm in a direction that is generally transverse to the direction from the hub to the free end of said arm.

21. The capacitor of claim 12, wherein said stator plates are planar and said rotor blades are planar.

22. The capacitor of claim 12, wherein said stator plates are circular about an axis and said rotor plates are circular about the same axis.