Self-stabilizing, floating microelectromechanical device

• US 20050241394A1
• Filed: 04/30/2004
• Published: 11/03/2005
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Clark, Jason Vaughn
• Granted Patent: US 7,225,674 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 5/00 Devices comprising elements which are movable in relation to each other, e.g. comprising slidable or rotatable elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

The present invention relates to MicroElectroMechanical Systems (MEMS), devices and applications thereof in which a proof mass is caused to levitate by electrostatic repulsion. Configurations of electrodes are described that result in self-stabilized floating of the proof mass. The electrical properties of the electrodes causing floating, such as currents and/or voltages, typically change in response to environmental perturbations affecting the proof mass. Measuring such currents and/or voltages allow immediate and accurate measurements to be performed related to those perturbations affecting the location and/or the orientation of the proof mass. Additional sensing electrodes can be included to further enhance sensing capabilities. Drive electrodes can also be included that allow forces to be applied to the charged proof mass resulting in a floating, electrically controllable MEMS device. Several applications are described including accelerometers, inertial sensors, resonators and filters for communication devices, gyros, one and two axis mirrors and scanners, among other devices. Several fabrication methods are also described.

Claims

1. A floating MEMS device comprising:

a) an electrostatically charged proof mass; and

,

b) at least two stabilizing electrode structures carrying charges that repel said charges on said proof mass, wherein

i) said proof mass is located with respect to said stabilizing electrode structures so as to levitate due to like-charge repulsion between said proof mass and said stabilizing electrode structures; and

wherein

ii) said proof mass and said stabilizing electrode structures are located so as to produce electrostatic repulsion leading to stable levitation such that displacements of said proof mass from its equilibrium floating position result in electrostatic forces on said proof mass tending to return said proof mass to said equilibrium position.

2. A floating MEMS device as in claim 1 further comprising a plurality of side electrodes disposed about the periphery of said proof mass, having first ends of said side electrodes integrally attached to said proof mass and having the opposite, second ends of said side electrodes projecting outward from said proof mass, and wherein said side electrodes carry at least a portion of said electrostatic charge of said proof mass, and wherein each of said second ends of said side electrodes project into one of said stabilizing electrode structures.

3. A floating MEMS device as in claim 2 wherein said side electrodes have termination blocks on said second ends thereof.

4. A floating MEMS device as in claim 3 wherein each of said stabilizing electrode structures comprise five blocks interacting electrostatically with said termination block of said side electrode.

5. A floating MEMS device as in claim 1 further comprising at least one sensor for detecting the position of said proof mass.

6. A floating MEMS device as in claim 5 wherein said at least one sensor comprises at least one device for measuring the electrical properties of at least one of said stabilizing electrode structures during operation of said FLEMS device.

7. A floating MEMS device as in claim 5 wherein said at least one sensor comprises at least one sensing electrode located in proximity to said proof mass.

8. A floating MEMS device as in claim 1 further comprising at least one drive electrode located so as to apply force to said proof mass under external control.

9. A floating MEMS device as in claim 2 further comprising at least one sensor for detecting the position of said proof mass.

10. A floating MEMS device as in claim 9 wherein said at least one sensor comprises at least one sensing electrode located in proximity to said proof mass.

11. A floating MEMS device as in claim 2 further comprising at least one drive electrode located so as to apply force to said proof mass under external control.

12. A floating MEMS device as in claim 2 wherein two side electrodes provide an axis of rotation for said proof mass.

13. A floating MEMS device as in claim 12 further comprising at least one drive electrode capable of providing force to said proof mass for rotation of said proof mass about said axis.

14. A device for measuring acceleration comprising a floating MEMS device as in claim 6.

15. A device for measuring acceleration comprising a floating MEMS device as in claim 7.

16. A resonator comprising a floating MEMS device as in claim 7 further comprising at least one drive electrode capable of driving said proof mass into a resonance mode.

17. A floating MEMS device as in claim 12 further comprising a third stabilizing electrode as a substantially circular track so as to allow said two side electrodes substantially free traverse around said track.

18. A floating MEMS device as in claim 17 further comprising at least one drive electrode located so as to apply force to said proof mass under external control.

19. A flux capacitor comprising an electrically charged rotor electrostatically levitated between two stators wherein said stators carry like charges as said rotor and wherein time-varying voltage applied to said stators is capable of causing said rotor to rotate.

20. A magnetometer comprising a flux capacitor as in claim 19 encompassed by a SQUID ring.