Direct charge radioisotope activation and power generation

• US 6,479,920 B1
• Filed: 04/09/2001
• Issued: 11/12/2002
• Est. Priority Date: 04/09/2001
• Status: Expired due to Term

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Li, Hui, Henderson, Douglass L., Blanchard, James P., Lal, Amit
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/832,342
• Publication Number:
  US 20030006668A1
• Time in Patent Office: 582 Days
• Field of Search: 310/302, 310/305, 310/309, 310/339, 376/320
• US Class Current: 310/309
• CPC Class Codes: G21H 1/00 Arrangements for obtaining electrical energy from radioactive sources, e.g. from radioactive isotopes , nuclear or atomic batteries
• CPC Class Codes: G21H 3/00 Arrangements for direct conversion of radiation energy from radioactive sources into forms of energy other than electric energy, e.g. into light or mechanic energy
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

An activator has a base on which is mounted an elastically deformable micromechanical element that has a section that is free to be displaced toward the base. An absorber of radioactively emitted particles is formed on the base or the displaceable section of the deformable element and a source is formed on the other of the displaceable section or the base facing the absorber across a small gap. The radioactive source emits charged particles such as electrons, resulting in a buildup of charge on the absorber, drawing the absorber and source together and storing mechanical energy as the deformable element is bent. When the force between the absorber and the source is sufficient to bring the absorber into effective electrical contact with the source, discharge of the charge between the source and absorber allows the deformable element to spring back, releasing the mechanical energy stored in the element. An electrical generator such as a piezoelectric transducer may be secured to the deformable element to convert the released mechanical energy to electrical energy that can be used to provide power to electronic circuits.

Claims

1. An activator comprising:

(a) a base;

(b) an elastically deformable element having a section spaced from the base that is free to be displaced toward the base from an initial position by elastic deformation of the deformable element;

(c) an absorber of radioactively emitted particles formed on one of the displaceable section of the deformable element and the base; and

(d) a material comprising a radioactive source formed on the other of the displaceable section of the deformable element and the base that faces the absorber across a gap, the radioactive source radioactively emitting charged particles, the deformable element capable of displacing in response to accumulated charge on the absorber such that at a sufficient charge the absorber effectively electrically contacts the source to discharge the absorber and allow the deformable element to return elastically to its initial position.

2. The activator of claim 1 wherein the gap is 1 mm or less.

3. The activator of claim 1 wherein the deformable element comprises a cantilever beam mounted at one end to a mounting block mounted to the base to support the cantilever beam above a surface of the base, the absorber or the source formed on the cantilever beam at a free end of the beam.

4. The activator of claim 1 wherein the deformable element comprises an elastically deformable bridge mounted to the base at two opposite ends of the bridge and having a central section that can be displaced toward the base by elastically deforming the bridge, the absorber or the source formed on the central section of the bridge.

5. The activator of claim 1 wherein the deformable element comprises an elastically deformable membrane having a periphery mounted to the substrate with the membrane spaced above a surface of the base, the membrane having a central section that can be displaced toward the base by elastically deforming the membrane, the absorber or the source formed on the central section of the membrane.

6. The activator of claim 1 wherein the deformable element is formed of a material selected from the group consisting of metal and silicon.

7. The activator of claim 1 wherein the absorber is formed of a conducting metal.

8. The activator of claim 1 wherein the material of the source is selected from the group consisting of nickel-63, ruthenium-106, phosphorous-32, phosphorous-33, sulfur-35, calcium-45, and tritium.

9. The activator of claim 1 wherein the material of the source is nickel-63.

10. The activator of claim 1 further including a piezoelectric transducer secured to the deformable element to deform therewith to develop an electrical potential across output terminals of the piezoelectric transducer.

11. The activator of claim 10 further including a coil connected to the output terminals of the piezoelectric transducer to form a resonant tank circuit therewith.

12. The activator of claim 11 including a sensor electrically connected between the absorber and the source, the sensor having an electrical resistance that changes with a sensed quantity to thereby affect the time required to charge the absorber sufficiently to deflect the deformable element sufficiently to contact the absorber to the source.

13. A power generator comprising:

(a) a base;

(b) an elastically deformable element having a section spaced from the base that is free to be displaced toward the base from an initial position by elastic deformation of the deformable element;

(c) an electrical generator coupled to the deformable element for developing an electrical potential across output terminals of the generator as the deformable element returns elastically to its initial position;

(d) an absorber of radioactively emitted particles formed on one of the displaceable section of the deformable element and the base; and

(e) a material comprising a radioactive source formed on the other of the displaceable section of the deformable element and the base that faces the absorber across a gap, the radioactive source radioactively emitting charged particles, the deformable element capable of displacing in response to accumulated charge on the absorber such that at a sufficient charge the absorber effectively electrically contacts the source to discharge the absorber and allow the deformable element to return elastically to its initial position.

14. The power generator of claim 13 wherein the electrical generator coupled to the deformable element is a piezoelectric transducer secured to the deformable element to deform therewith.

15. The power generator of claim 13 wherein the deformable element comprises a cantilever beam mounted at one end to a mounting block mounted to the base to support the cantilever beam above a surface of the base, the absorber or the source formed on the cantilever beam at a free end of the beam.

16. The power generator of claim 13 wherein the deformable element comprises an elastically deformable bridge mounted to the base at two opposite ends of the bridge and having a central section that can be displaced toward the base by elastically deforming the bridge, the absorber or the source formed on the central section of the bridge.

17. The power generator of claim 13 wherein the deformable element comprises an elastically deformable membrane having a periphery mounted to the substrate with the membranes spaced above a surface of the base, the membrane having a central section that can be displaced toward the base by elastically deforming the membrane, the absorber or the source formed on the central section of the membrane.

18. The power generator of claim 13 wherein the deformable element is formed of a material selected from the group consisting of metal and silicon.

19. The power generator of claim 13 wherein the absorber is formed of a conducting metal.

20. The power generator of claim 13 wherein the material of the source is selected from the group consisting of nickel-63, ruthenium-106, phosphorous-32, phosphorous-33, sulfur-35, calcium-45, and tritium.

21. The power generator of claim 13 wherein the material of the source is nickel-63.

22. The power generator of claim 14 further including a coil connected to the output terminals of the piezoelectric transducer to form a resonant tank circuit therewith.

23. The power generator of claim 22 including a sensor electrically connected between the absorber and the source, the sensor having an electrical resistance that changes with a sensed quantity to thereby affect the time required to charge the absorber sufficiently to deflect the deformable element sufficiently to effectively electrically contact the absorber and the source.

24. The power generator of claim 13 wherein the electrical generator coupled to the deformable element is a piezoelectric transducer-secured to the deformable element to deform therewith, and including a rectifier connected to terminals of the piezoelectric transducer to rectify the output therefrom to a DC voltage, and a storage capacitor connected to receive the DC voltage from the rectifier.

30. The micromechanical power generator of claim 24 further including a coil connected to the output terminals of the piezoelectric transducer to form a resonant tank circuit therewith.

25. A micromechanical power generator comprising:

(a) a base;

(b) an elastically deformable micromechanical cantilever beam mounted at one end to a mounting block mounted to the base to support the cantilever beam above a surface of the base and having a free end that is free to be displaced toward the base from an initial position by elastic deformation of the beam;

(c) a piezoelectric transducer secured to the cantilever beam to deform therewith to develop an electrical potential across output terminals of the piezoelectric transducer;

(d) an absorber of radioactively emitted particles formed on one of the free end of the cantilever beam and the base; and

(e) a material comprising a radioactive source formed on the other of the free end of the cantilever beam and the base facing the absorber across a gap of 1 mm or less, the radioactive source radioactively emitting charged particles, the deformable element capable of displacing in response to accumulated charge on the absorber such that at a sufficient charge the absorber effectively electrically contacts the source to discharge the absorber and allow the cantilever beam to return elastically to its initial position.

26. The micromechanical power generator of claim 25 wherein the cantilever beam is formed of a material selected from the group consisting of metal and silicon.

27. The micromechanical power generator of claim 25 wherein the absorber is formed of a conducting metal.

28. The micromechanical power generator of claim 25 wherein the material of the source is selected from the group consisting of nickel-63, ruthenium-106, phosphorous-32, phosphorous-33, sulfur-35, calcium-45, and tritium.

29. The micromechanical power generator of claim 25 wherein the material of the source is nickel-63.

31. The micromechanical power generator of claim 25 including a sensor electrically connected between the absorber and source, the sensor having an electrical resistance that changes with a sensed quantity to thereby affect the time required to charge the absorber sufficiently to deflect the deformable element sufficiently to contact the absorber to the source.

32. The micromechanical power generator of claim 25 including a rectifier connected to the terminal of the piezoelectric transducer to rectify the output therefrom to a DC voltage, and a storage capacitor connected to receive the DC voltage from the rectifier.

33. A method of generating electrical power suited for use in microelectromechanical systems comprising:

(a) impinging charged particles emitted from a radioisotope source onto an absorber to draw the absorber and the source toward one another from the electrostatic force from the charge built-up on the absorber, one of the source and absorber formed on an elastically deformable element, the electrostatic force between the absorber and the source elastically deforming the micromechanical element to store mechanical energy in the element, until the absorber is brought into effective electrically conductive contact with the source to discharge the charge accumulated on the absorber and allow the deformable element to elastically return toward an initial position, releasing the mechanical energy stored in the deformable element; and

(b) transferring energy from the elastically deformable element as it elastically returns toward its initial position to an electrical generator coupled to the deformable element to generate electrical power at output terminals of the electric generator.

34. The method of claim 33 wherein the electrical generator is a piezoelectric transducer secured to the deformable element to deform therewith.

35. The method of claim 34 further comprising rectifying the output electrical power from the piezoelectric transducer and storing the rectified power on a storage capacitor.

36. The method of claim 33 wherein the elastically deformable element is a cantilever beam, and wherein the absorber is formed on a free end of the beam and draws the free end of the beam toward the source until the absorber comes into effective electrically conductive contact with the source.