Biocompatible Copper-Based Shape Memory Alloys via Oxide Coating
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Solution Overview
Problem
Copper-based shape memory alloys (SMAs) are considered cytotoxic due to their high copper content, making them unsuitable for medical applications despite their desirable properties such as extreme flexibility, which is essential for medical devices like archwires and guidewires.
Innovation Solution
Forming a durable aluminum oxide surface layer on single-crystal copper-aluminum-nickel SMAs to inhibit body fluid reactions and corrosion, similar to titanium oxide in Nitinol, thereby making them biocompatible for medical use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If copper-based shape memory alloys are used to achieve extreme flexibility and shape recovery, then the material properties are improved, but cytotoxicity and biocompatibility worsen
Solution Approach 1:
The patent applies composite materials by combining copper-based shape memory alloy with a biocompatible coating layer (such as titanium nitride, diamond-like carbon, or other biocompatible materials). This composite structure allows the core copper-based alloy to provide extreme flexibility and shape recovery properties, while the outer coating layer provides biocompatibility and prevents cytotoxicity. The coating acts as a barrier between the copper-based alloy and biological tissues, eliminating direct contact and associated toxic effects.
Solution Approach 2:
The patent uses an intermediary approach by introducing a biocompatible coating layer as a mediator between the copper-based shape memory alloy and the biological environment. This coating layer serves as an intermediate barrier that prevents direct interaction between copper ions and living tissues, thereby eliminating cytotoxicity while allowing the underlying copper-based alloy to maintain its superior mechanical properties including flexibility and shape recovery.
2Strength
If copper-based shape memory alloys are used to achieve hyperelastic behavior, then the mechanical performance is improved, but corrosion resistance worsens
Solution Approach 1:
The patent applies composite materials by combining copper-based shape memory alloy with a protective coating layer that provides corrosion resistance. The copper-based alloy core maintains hyperelastic behavior and mechanical strength, while the outer coating layer (such as titanium nitride, diamond-like carbon, or other corrosion-resistant materials) provides a barrier against corrosive body fluids. This composite structure allows both high mechanical performance and reliable corrosion resistance to coexist.
Solution Approach 2:
The patent uses an intermediary approach by introducing a corrosion-resistant coating layer as a mediator between the copper-based shape memory alloy and the corrosive biological environment. This coating layer serves as a protective intermediate barrier that prevents direct contact between copper-based alloy and corrosive body fluids, thereby eliminating corrosion issues while allowing the underlying copper-based alloy to maintain its superior hyperelastic mechanical properties.
3Object-affected harmful factors
If nickel-titanium SMAs are used to ensure biocompatibility, then safety is improved, but flexibility and shape recovery capability worsen
Solution Approach 1:
The patent applies composite materials by combining copper-based shape memory alloy with a biocompatible coating layer. The copper-based alloy core provides superior flexibility and shape recovery capability that exceeds nickel-titanium alloys, while the outer coating layer provides biocompatibility. This composite structure allows the device to achieve both high flexibility and biocompatibility, overcoming the limitations of nickel-titanium SMAs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The biocompatible copper-based SMAs demonstrate negative results in cytotoxicity, systemic toxicity, hemocompatibility, and implantation tests, ensuring they can be used in medical devices without causing toxic damage to tissues or corrosion, with enhanced corrosion resistance and flexibility.
Implementation Method 1
forming a durable aluminum oxide surface layer on single-crystal copper-aluminum-nickel SMAs to inhibit body fluid reactions and corrosion
Data Source
AI summary
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.