A Shape Memory Alloy MEMS Heat Engine

• US 20060162331A1
• Filed: 01/27/2005
• Published: 07/27/2006
• Est. Priority Date: 01/27/2005
• Status: Active Grant

• Current Assignee: Azad Siahmakoun, Scott Ryan Kirkpatirck, Thomas Mcdaniel Adams, Zhefu Wang
• Original Assignee: Azad Siahmakoun, Scott Ryan Kirkpatirck, Thomas Mcdaniel Adams, Zhefu Wang
• Inventors: Siahmakoun, Azad, Kirkpatirck, Scott Ryan, Wang, Zhefu, Adams, Thomas McDaniel
• Granted Patent: US 7,444,812 B2
• Time in Patent Office: Days
• US Class Current: 60/527
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: F04D 33/00 Non-positive-displacement pumps with other than pure rotation, e.g. of oscillating type F04D35/00 takes precedence; hand-held fans A45B

Abstract

A microelectromechanical systems (MEMS) based heat engine capable of converting thermal energy gradients into mechanical or electrical energy, as well as its fabrication process is disclosed. This heat engine design consists of a stressed oscillating beam formed from a shape memory alloy (SMA) thin film. As the temperature of the beam changes, its shape changes due to the phase transformation of the shape memory alloy, causing it to oscillate between a hot source and a cold source. Due to the hysteretic behavior of the phase transformation, the oscillating SMA cantilever beam produces a net mechanical work output that may be either converted to electrical energy or mechanically linked to other MEMS devices.

Claims

1. An oscillating shape memory alloy heat engine comprising;

an oscillating member

wherein said member has a dimension less than 100 microns

wherein a first portion of said member comprises a shape memory alloy

a heat source

a cold source.

2. The oscillating heat engine of claim 1 wherein said oscillating member contains at least one thin film.

3. The oscillating heat engine of claim 1 wherein said oscillating member contains a cantilever beam.

4. The oscillating heat engine of claim 1 wherein said cold source is a substrate.

5. The oscillating heat engine of claim 1 wherein said shape memory alloy is Nitinol.

6. The oscillating heat engine of claim 1 wherein said oscillating member has a bi-layer structure.

7. The oscillating heat engine of claim 1 wherein said oscillating member has an externally applied load.

8. The oscillating heat engine of claim 6 wherein said bi-layer structure has a first layer and a second layer,

wherein said first layer has a different thermal expansion coefficient than said second layer.

9. The oscillating heat engine of claim 8 wherein said first portion of said oscillating member is the first layer.

10. The oscillating heat engine of claim 1 wherein said oscillating member is a variable capacitor.

11. The oscillating heat engine of claim 1 wherein said oscillating member has a second portion;

wherein said second portion has a magnetic permeability greater than air.

12. The oscillating heat engine of claim 11 wherein said second portion contains iron.

13. The oscillating heat engine of claim 11 wherein said second portion contains cobalt.

14. The oscillating heat engine of claim 11 wherein said second portion contains nickel.

15. The oscillating heat engine of claim 10 wherein said variable capacitor is part of a variable capacitive electrostatic generator.

16. The oscillating heat engine of claim 11 wherein said second member is part of an inductive electrical generator.

17. A method of producing self assembled devices comprising;

depositing a first layer on a substrate;

depositing a second layer thus forming a shape;

wherein said first and second layers have different thermal expansion coefficients;

changing temperature of the layers by at least 10 degrees centigrade;

wherein said changing of the temperature changes the shape.

18. The method as claimed in claim 17 wherein said self assembled device is a heat engine.

19. The method of claim 17 wherein said shape change moves a second device.

20. The method of claim 17 wherein said shape change creates a vertical change in shape.

21. The method of claim 17 wherein said shape change is a horizontal change in shape.