Electrostatically tunable resonance frequency beam utilizing a stress-sensitive film

• US 6,263,736 B1
• Filed: 09/24/1999
• Issued: 07/24/2001
• Est. Priority Date: 09/24/1999
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Energy Systems, Inc. (AES Corporation)
• Original Assignee: UT-Battelle LLC
• Inventors: Davis, J. Kenneth, Wachter, Eric A., Thundat, Thomas G.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/404,954
• Time in Patent Office: 669 Days
• Field of Search: 735/143.6, 735/143.4, 735/142.6, 735/141.7, 735/141.8, 310/309, 361/280, 361/283.1, 361/287
• US Class Current: 73/514.36
• CPC Class Codes: G01H 1/14 Frequency
• CPC Class Codes: G01H 11/06 by electric means
• CPC Class Codes: G01H 3/04 Frequency

Abstract

Methods and apparatus for detecting particular frequencies of acoustic vibration utilize an electrostatically-tunable beam element having a stress-sensitive coating and means for providing electrostatic force to controllably deflect the beam element thereby changing its stiffness and its resonance frequency. It is then determined from the response of the electrostatically-tunable beam element to the acoustical vibration to which the beam is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.

Claims

1. An electrostatically-tunable beam for detecting a particular frequency of acoustic vibration out of a mixture of frequencies comprising:

a beam element having an end and a surface, and being fixedly disposed on the end;

a stress-sensitive means for sensing stress selected from the group consisting of;

a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffness that varies with the stress therein;

a first electrical conductor means for conducting electricity selected from the group consisting of;

an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material;

a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween;

electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend, thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam.

2. The electrostatically-tunable beam as described in claim 1 wherein the beam element comprises a cantilever beam.

3. The electrostatically-tunable beam as described in claim 1 wherein the stress-sensitive coating is selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

4. The electrostatically-tunable beam as described in claim 1 wherein the stress-sensitive cantilever beam material is selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

5. The electrostatically-tunable beam as described in claim 1 wherein the conductive coating is selected from the group consisting of conductive metals and conductive alloys of metals.

6. The electrostatically-tunable beam as described in claim 1 further comprising detection means for detecting vibration of the beam element.

7. The electrostatically-tunable beam as described in claim 6 wherein the detection means is selected from the group consisting of optical detection means, means utilizing changes in piezoresistance of the stress sensitive means and means utilizing changes in tunneling current between the electrostatically-tunable beam and a stationary electrode.

8. The electrostatically-tunable beam as described in claim 1 wherein the electrical potential means is disposed and connected to provide electrical potentials of opposite polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic attraction therebetween.

9. The electrostatically-tunable beam as described in claim 1 wherein the electrical potential means is disposed and connected to provide electrical potentials of like polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic repulsion therebetween.

10. A method for detecting a particular frequency of acoustical vibration in a mixture of frequencies comprising the steps of:

a. providing an electrostatically-tunable beam comprising a beam element having an end and a surface and being fixedly disposed on the end;

a stress-sensitive means for sensing stress selected from the group consisting of;

a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffness that varies with the stress therein;

a first electrical conductor means for conducting electricity selected from the group consisting of;

an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material;

a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween; and

electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means;

b. exposing the beam element to the mixture of frequencies;

c. activating the electrical potential means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam to permit the electrostatically-tunable beam to respond resonantly at the particular frequency; and

d. determining from the resonance response of the electrostatically-tunable beam whether the particular frequency of vibration is detected.

11. The method as described in claim 10 wherein the beam element comprises a cantilever beam.

12. The method as described in claim 10 wherein the stress-sensitive coating is selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

13. The method as described in claim 10 wherein the stress-sensitive cantilever beam material is selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

14. The method as described in claim 10 wherein the conductive coating is selected from the group consisting of conductive metals and conductive alloys of metals.

15. The method as described in claim 10 further comprising the step of utilizing means for detecting vibration of the beam element.

16. The method as described in claim 15 wherein the detection means is selected from the group consisting of optical detection means, means utilizing changes in piezoresistance of the cantilever beam and means utilizing changes in tunneling current between the electrostatically-tunable beam and a stationary electrode.

17. The method as described in claim 10 wherein the electrical potential means is disposed and connected to provide electrical potentials of opposite polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic attraction therebetween.

18. The method as described in claim 10 wherein the electrical potential means is disposed and connected to provide electrical potentials of like polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic repulsion therebetween.

19. A method for selecting a desired frequency of acoustical vibration from a mixture of frequencies comprising the steps of:

a. providing an electrostatically-tunable beam comprising a beam element having an end and a surface, and being fixedly disposed on the end;

a stress-sensitive means for sensing stress selected from the group consisting of;

a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffness that varies with the stress therein;

a first electrical conductor means for conducting electricity selected from the group consisting of;

an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material;

a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween; and

electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means;

b. activating the electrical potential means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam to establish the resonance frequency of the electrostatically-tunable beam at the desired frequency; and

c. exposing the electrostatically-tunable beam to the mixture of frequencies to excite the electrostatically-tunable beam to vibrate at a desired resonance frequency whereby the particular frequency desired is selected out of the mixture of frequencies.

20. The method as described in claim 19 wherein the beam element comprises a cantilever beam.

21. The method as described in claim 19 wherein the stress-sensitive coating selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

22. The method as described in claim 19 wherein the stress-sensitive cantilever beam material is selected from the group consisting of metals, metal alloys, dielectric materials, polymeric materials and combinations thereof.

23. The method as described in claim 19 wherein the conductive coating is selected from the group consisting of conductive metals and conductive alloys of metals.

24. The method as described in claim 19 further comprising the step of utilizing means for detecting vibration of the beam element.

25. The method as described in claim 24 wherein the detection means is selected from the group consisting of optical detection means, means utilizing changes in piezoresistance of the cantilever beam and means utilizing changes in tunneling current between the electrostatically-tunable beam and a stationary electrode.

26. The method as described in claim 19 wherein the electrical potential means is disposed and connected to provide electrical potentials of opposite polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic attraction therebetween.

27. The method as described in claim 19 wherein the electrical potential means is disposed and connected to provide electrical potentials of like polarity upon the first electrical conductor means and the second electrical conductor means to cause electrostatic repulsion therebetween.