Shape memory alloy thin film, method of fabrication, and articles of manufacture

• US 7,540,899 B1
• Filed: 05/24/2006
• Issued: 06/02/2009
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Monarch Biosciences, Inc.
• Original Assignee: TiNi Alloy Company
• Inventors: Johnson, A David
• Primary Examiner(s): WYSZOMIERSKI, GEORGE P
• Application Number:
  US11/420,157
• Time in Patent Office: 1,105 Days
• Field of Search: None
• US Class Current: 75/10.11
• CPC Class Codes: A61L 2400/16 Materials with shape-memory or superelastic properties
• CPC Class Codes: A61L 27/04 Metals or alloys
• CPC Class Codes: A61L 27/50 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: A61L 31/022 Metals or alloys
• CPC Class Codes: A61L 31/14 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: C21D 2201/01 Shape memory effect
• CPC Class Codes: C22B 9/223 by laser beams working by laser beam B23K26/00
• CPC Class Codes: C22C 1/11 Making amorphous alloys
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22C 19/03 based on nickel
• CPC Class Codes: C23C 14/165 by cathodic sputtering
• CPC Class Codes: C23C 14/34 Sputtering
• CPC Class Codes: C23C 14/5806 Thermal treatment
• CPC Class Codes: C30B 1/023 from solids with amorphous structure
• CPC Class Codes: C30B 29/52 Alloys

Abstract

A method of forming a single crystal in a thin film by progressively rapidly heating (and cooling) a narrow band of amorphous material. The amorphous thin film may be of shape memory alloy such as TiNi or CuAlNi. Heating may be accomplished by a line-focused laser beam. The thin film may be formed by sputter deposition on a substrate such as silicon. The thin film crystal that is formed has non-isotropic stress/strain characteristics, and very large recoverable strain in a preferred direction. The single crystal SMA exhibits greater strain recovery; Constant force deflection; Wider transition temperature range; Very narrow loading hysteresis; and Recovery that is repeatable & complete. Single Crystal SMA is manufactured by pulling a single crystal from melt, a method similar to that used by the semiconductor industry to fabricate silicon boules. This process enables manufacture of materials that approach theoretical limits.

Claims

1. A method for making a single crystal shape memory alloy thin film comprising the steps of:

depositing a thin film layer of amorphous shape memory alloy material on a substrate;

applying a strip of heat to the amorphous shape memory alloy material to form a crystallization front along the strip;

moving the strip of heat across the amorphous shape memory alloy material in a direction to move the crystallization front across the material;

crystallizing the amorphous material into crystallized material having a single crystal crystallographic orientation; and

cooling the crystallized material with a heat sink.

2. The method of claim 1 wherein the crystallization step comprises using a seed crystal to initiate the crystallization process.

3. The method of claim 1 wherein the crystallized material is superelastic at room temperature.

4. The method of claim 1 wherein the shape memory alloy material is initially a polycrystalline shape memory alloy.

5. The method of claim 1 in which the heat is provided by a device selected from the group consisting of:

laser, infrared wavelength light source, visible wavelength light source.

6. The method of claim 1 in which the heat is provided by a scanning electron beam.

7. A method for forming a thin film, single crystal shape metal alloy comprising the steps of:

sputter depositing a thin film of amorphous shape memory alloy material onto a substrate;

heating the thin film amorphous shape memory alloy material with a narrow band of heat so that it reaches its crystallization temperature in the narrow band;

moving the narrow band of heat across the thin film to create a moving crystallization front having a single crystal crystallographic orientation; and

cooling behind the crystallization front to stabilize the single crystal crystallographic orientation formed.

8. The method of claim 7 further comprising using a seed crystal as a starting material.

9. The method of claim 7 wherein the crystallized material is superelastic at room temperature.

10. The method of claim 7 wherein the shape memory alloy material is initially a polycrystalline shape memory alloy.

11. A method of manufacturing a device having a thin film of single crystal shape memory alloy comprising the steps of:

depositing a layer of amorphous shape memory alloy material on a substrate;

applying a strip of heat to a portion of the amorphous material to form a crystallization front along the strip;

moving the strip of heat across the amorphous shape memory alloy material to move the crystallization front across the material;

crystallizing the amorphous shape memory alloy material into a single crystal crystallographic orientation;

cooling the material behind the crystallization front with a heat sink; and

manufacturing a device from the crystallized material.

12. The method according to claim 11 wherein the device is selected from the group consisting of:

microactuator, valve, electric switch, relay, optical switch, stent, stent covers, and anastomosis devices.

13. The method of claim 12 wherein the shape memory alloy material is initially a polycrystalline shape memory alloy.