Biocompatible copper-based single-crystal shape memory alloys

• US 8,556,969 B2
• Filed: 12/01/2008
• Issued: 10/15/2013
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: Ormco Corporation (Envista Holdings Corporation)
• Original Assignee: Ormco Corporation (Envista Holdings Corporation)
• Inventors: Johnson, Alfred David
• Primary Examiner(s): Isabella, David
• Assistant Examiner(s): Ganesan, Suba
• Application Number:
  US12/325,722
• Publication Number:
  US 20090187243A1
• Time in Patent Office: 1,779 Days
• Field of Search: 623/11.11, 148/562, 148/563, 148/402, 427/2.27, 427/453, 427/529
• US Class Current: 623/11.11
• CPC Class Codes: A61L 2400/16 Materials with shape-memory or superelastic properties
• CPC Class Codes: A61L 27/047 Other specific metals or alloys not covered by A61L27/042 - A61L27/045 or A61L27/06
• 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: C22C 9/01 with aluminium as the next major constituent
• CPC Class Codes: C30B 15/00 Single-crystal growth by pulling from a melt, e.g. Czochralski method under a protective fluid C30B27/00
• CPC Class Codes: C30B 15/36 characterised by the seed, e.g. its crystallographic orientation
• CPC Class Codes: C30B 29/52 Alloys
• CPC Class Codes: C30B 31/00 Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
• CPC Class Codes: C30B 33/005 Oxydation

Abstract

We describe herein biocompatible single crystal Cu-based shape memory alloys (SMAs). In particular, we show biocompatibility based on MEM elution cell cytotoxicity, ISO intramuscular implant, and hemo-compatibility tests producing negative cytotoxic results. This biocompatibility may be attributed to the formation of a durable oxide surface layer analogous to the titanium oxide layer that inhibits body fluid reaction to titanium nickel alloys, and/or the non-existence of crystal domain boundaries may inhibit corrosive chemical attack. Methods for controlling the formation of the protective aluminum oxide layer are also described, as are devices including such biocompatible single crystal copper-based SMAs.

Claims

1. A biocompatible device for use within a body comprising a single crystal copper-based shape memory alloy having an exposed outer surface at and below which resides a surface region of depth greater than 1 nm below the exposed outer surface that is enriched in aluminum relative to copper, wherein the aluminum enriched in the surface region of the single crystal copper-based shape memory alloy is in the form of aluminum oxide thereby forming a protective outer layer comprising aluminum oxide greater than 1 nm thick that is formed at least in part by oxidizing the aluminum enriched in the surface region of the single crystal.

2. The device of claim 1, wherein the single-crystal copper-based shape memory material comprises CuAlNi.

3. The device of claim 1, wherein the protective outer layer comprising aluminum oxide is an amorphous layer of aluminum oxide.

4. The device of claim 1, wherein the protective outer layer comprising aluminum oxide is substantially crystalline aluminum oxide.

5. The device of claim 1, wherein the protective outer layer comprising aluminum oxide is greater than 100 nm thick.

6. The device of claim 1, wherein the single crystal copper-based shape memory alloy is configured as at least one of:

a joint replacement, a hip bone replacement, a guidewire, a clot retriever, a blood filter, a stent, and a dental arch.

7. The device of claim 1, wherein the depth of the surface region is greater than 10 nm below the exposed outer surface.

8. A method of forming the biocompatible device of claim 1, the method comprising the steps of:

forming the single crystal copper-based shape memory alloy from a seed of copper aluminum based alloy aligned on the <

100>

crystallographic direction; and

forming the protective outer layer comprising aluminum oxide in the surface region of the single crystal copper-based shape memory alloy by a controlled process of doping the surface region with Al after forming the single crystal copper-based shape memory alloy, anodizing the surface region of the single crystal copper-based shape memory alloy, and/or applying a high voltage to the single crystal copper-based shape memory alloy.

9. A biocompatible dental arch comprising a copper-aluminum single crystal shape memory alloy having an exposed outer surface from which extends a surface region of depth greater than 1 nm below the outer surface of the single crystal shape memory alloy that is enriched in aluminum relative to copper, wherein the surface region provides a protective outer layer comprising aluminum oxide formed at least in part by oxidizing the aluminum enriched in the surface region of the single crystal.

10. The device of claim 9, wherein the protective outer layer comprising aluminum oxide is greater than 10 nm thick.

11. The device of claim 9, wherein the single-crystal copper-based shape memory material comprises CuAlNi, and the protective outer layer comprising aluminum oxide is an amorphous layer of aluminum oxide of thickness greater than 100 nm.

12. The device of claim 9, wherein the single-crystal copper-based shape memory material comprises CuAlNi, and the protective outer layer comprising aluminum oxide is substantially crystalline aluminum oxide of thickness greater than 100 nm.