Diffusion Bonding Shape Memory Alloy Medical Device Components
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Solution Overview
Problem
Existing methods for attaching barbs to intraluminal prostheses, such as stent grafts, face challenges like corrosion, mechanical stress-induced failures, and heat-affected zones from laser welding, which can lead to embrittlement and increased likelihood of barb failure.
Innovation Solution
A bonding method using shape memory materials that involves positioning components in close proximity, heat treating them between 800° C. to 1100° C. to form a diffusion bond, and then heat-setting at 350° C. to 550° C. to impart a desired shape without impairing the bond, utilizing a press-fit and internal pressure generated by thermal expansion for enhanced bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soldering is used to attach barbs to struts, then mechanical attachment strength is improved, but corrosion resistance deteriorates due to contact with bodily fluids
Solution Approach 1:
The patent introduces a nickel coating layer as an intermediary between the stainless steel strut and the nickel-titanium alloy barb. This intermediate layer prevents direct contact between dissimilar metals, eliminating galvanic corrosion while maintaining strong metallurgical bonds. The nickel coating serves as a protective barrier that preserves both the mechanical strength of the attachment and the corrosion resistance required for biomedical applications.
2Productivity
If laser welding is used to attach barbs to struts, then attachment speed and precision are improved, but heat-affected zone causes embrittlement and increases failure risk
Solution Approach 1:
The patent replaces the thermal field of laser welding with a mechanical field approach using diffusion bonding. By heating the components to elevated temperatures (but below melting point) and applying pressure to create intimate contact, metallurgical bonds form through atomic diffusion without the localized melting and rapid cooling that cause embrittlement. This substitution of bonding mechanism eliminates the harmful heat-affected zone while maintaining attachment strength and material toughness.
3Reliability
If mechanical attachment methods are used for barbs, then corrosion resistance is improved, but reliability under repetitive mechanical stress deteriorates due to fracture
Solution Approach 1:
The patent changes the bonding parameters from room-temperature mechanical assembly to elevated-temperature diffusion bonding. By increasing the temperature to facilitate atomic diffusion and applying controlled pressure, the components form a metallurgical bond that is as strong as or stronger than the base materials themselves. This parameter change transforms the attachment from a weak mechanical connection susceptible to fatigue fracture into a robust integrated structure that can withstand repetitive mechanical stresses in the cardiovascular environment.
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
This method creates a strong, reliable bond between shape memory alloy components, reducing the risk of barb failure and maintaining superelastic properties, thus ensuring secure anchoring of medical devices in the body.
Implementation Method 1
The assembled configuration is heat treated at a temperature in the range of from about 800° C. to about 1100° C. to obtain a bond between the first component and the second component at a region of contact therebetween
Implementation Method 2
The assembled configuration is then formed into a desired set shape and heat-set at a temperature in the range of from about 350° C. to about 550° C. Accordingly, a memory of the desired set shape is imparted to the shape memory material
Implementation Method 3
utilizing a press-fit and internal pressure generated by thermal expansion for enhanced bonding
Data Source
AI summary
A method of bonding a first component of a medical device to a second component of the medical device, where at least one of the components comprises a shape memory material, includes positioning the components in close proximity to each other to obtain an assembled configuration, and heating the assembled configuration at a temperature in the range of from about 800° C. to about 1100° C. to obtain a diffusion bond at a region of contact between the two components. The assembled configuration is formed into a desired set shape and heat-set at a temperature in the range of from about 350° C. to about 550° C. to impart a memory of the desired set shape to the shape memory materials without substantially impairing the diffusion bond.