Energy harvesting device and methods

• US 20070125176A1
• Filed: 12/02/2005
• Published: 06/07/2007
• Est. Priority Date: 12/02/2005
• Status: Abandoned Application

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Liu, Yue
• Application Number:
  US11/292,615
• Publication Number:
  US 20070125176A1
• Time in Patent Office: Days
• US Class Current: 73/649
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

An energy harvesting device and related methods, with one embodiment comprising a micro-electromechanical structure fabricated as a plurality of members respectively resonant at different frequencies so that the structure can respond to a number of different vibration frequencies. Piezoelectric material converts the vibrations into an electric voltage difference across at least a portion of the structure.

Claims

1. An energy harvesting device comprising:

piezoelectric material capable of converting vibrations into an electric voltage difference across at least a portion of the device;

a plurality of members;

a first member of the plurality of members resonant at a first frequency;

a second member of the plurality of members resonant at a second frequency that is different than the first frequency.

2. The energy harvesting device as in claim 1,

the plurality of members comprising at least three members;

each of the members respectively resonant at a different frequency than the frequencies at which the other members are resonant.

3. The energy harvesting device as in claim 1, wherein the first frequency does not exceed about one kilohertz.

4. The energy harvesting device as in claim 1, wherein no linear dimension of any of the members exceeds about ten millimeters.

5. The energy harvesting device as in claim 1, wherein the plurality of members comprises an array of beams.

6. The energy harvesting device as in claim 1, wherein each of the plurality of members is composed at least partially of silicon.

7. The energy harvesting device as in claim 1, wherein the piezoelectric material comprises a surface film on at least part of the device.

8. The energy harvesting device as in claim 1, further comprising:

a first rectifying circuit;

a second rectifying circuit;

the first rectifying circuit electrically coupled with the first member;

the second rectifying circuit electrically coupled with the second member.

9. A method for making an energy harvesting device, the method comprising:

creating a micro-electromechanical array of beams using integrated circuit manufacturing technology;

designing each of the beams to be resonant respectively at a different frequency than the frequencies at which the other beams are resonant;

coating at least part of each of the beams with a piezoelectric material capable of converting vibrations into an electric voltage difference across at least a portion of the array.

10. The method as in claim 9, further comprising:

electrically coupling the piezoelectric material coating of each beam to a separate rectifying circuit.

11. The method as in claim 10, further comprising:

integrating the rectifying circuits and the array of beams on a single chip.

12. The method as in claim 9, wherein the array comprises at least three beams.

13. The method as in claim 9, wherein a resonant frequency of a first beam of the array does not exceed about one kilohertz.

14. The method as in claim 9, wherein none of the beams is longer than about ten millimeters.

15. The method as in claim 9, wherein the array is composed at least partially of silicon.

16. The method as in claim 9, wherein

the creating process comprises forming silicon dioxide layers on a top and a bottom of a silicon wafer using a wet oxidation process;

the coating process comprises depositing the piezoelectric material on the top by repeated sol-gel processes;

the creating process further comprises using a sputtering process to deposit a bottom electrode on the top silicon dioxide layer before performing the coating step, and to deposit a top electrode after performing the coating step;

the creating process further comprises forming top-side device patterns using photolithography patterning techniques and etch processes;

the creating process further comprises selectively removing bulk silicon from the bottom of the wafer to form the beams with desired thicknesses.

17. A method for supplying electric energy to a system, the method comprising:

electrically connecting the system to a micro-electromechanical structure (MEMS);

the MEMS comprising a plurality of members;

each member of at least some of the plurality of members being resonant respectively at a different frequency than the frequencies at which the other members are resonant;

the MEMS comprising piezoelectric material capable of converting vibrations at any of the resonant frequencies into an electric voltage difference across at least a portion of the MEMS.

18. The method as in claim 17, further comprising:

separately rectifying a voltage across any of the plurality of members.

19. The method as in claim 17, wherein the plurality of members comprises at least three members.

20. The method as in claim 17, wherein a resonant frequency of a first member of the plurality of members does not exceed about one kilohertz.

21. The method as in claim 17, wherein no linear dimension of any of the members exceeds about ten millimeters.

22. The method as in claim 17, wherein the plurality of members comprises an array of beams.

23. The method as in claim 17,

each of the plurality of members being composed at least partially of silicon;

the piezoelectric material comprising a surface film on at least part of the MEMS.

24. An energy harvesting device comprising:

a micro-electromechanical means for resonating at a number of different vibration frequencies;

a means for converting vibrations into an electric voltage difference across at least a portion of the device.

25. The energy harvesting device as in claim 24,

the resonating means comprising at least three members;

each of at least some of the members respectively resonant at a different frequency than the frequencies at which the other members are resonant.

26. A sensor for sensing a desired parameter, the sensor comprising:

a sensing member capable of sensing the desired parameter;

a plurality of vibrating members;

each member of at least some of the plurality of vibrating members being resonant respectively at a different frequency than the frequencies at which the other vibrating members are resonant;

piezoelectric material capable of converting vibrations at any of the resonant frequencies into an electric voltage difference across at least a portion of the sensor, and providing electric energy for operation of the sensor.

27. The sensor as in claim 26, further comprising:

a battery;

the energy provided by the piezoelectric material capable of supplementing energy available from the battery.

28. The sensor as in claim 26, wherein a resonant frequency of a first vibrating member of the plurality of resonant members does not exceed about one kilohertz.

29. The sensor as in claim 26, wherein no linear dimension of any of the vibrating members exceeds about ten millimeters.

30. The sensor as in claim 26, wherein the plurality of vibrating members comprises an array of beams.

31. The sensor as in claim 26,

each of the plurality of vibrating members being composed at least partially of silicon;

the piezoelectric material comprising a surface film on at least part of the sensor.

32. The sensor as in claim 26, further comprising:

a plurality of rectifying circuits;

each rectifying circuit electrically coupled respectively with one of the plurality of vibrating members.