Nitinol Component Coupling by Superelastic Interference Fit
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Solution Overview
Problem
The challenge lies in effectively coupling nitinol components to dissimilar materials in medical devices due to the hard oxide outer layer of nitinol, which limits bonding and can create weak points, especially when using filler materials that may deteriorate nitinol's thermal properties.
Innovation Solution
A method involving altering the nitinol component by reducing its cross-sectional dimension through stretching, allowing it to fit into a receiving component, and then allowing it to revert to its original state, thereby securely coupling without the need for adhesives or heat exposure, utilizing the superelastic properties of nitinol to maintain the bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive bonding or welding is used to couple nitinol to dissimilar materials, then the components can be joined, but the hard oxide outer layer of nitinol limits bonding and creates weak points
Solution Approach 1:
The patent applies parameter changes by transforming the nitinol wire from its natural state to an altered state through stretching, which reduces its cross-sectional dimension. This physical parameter change allows the wire to be inserted through the opening in the receiver component, and upon recovery, creates a secure mechanical interference fit that eliminates bonding weak points while maintaining bond strength.
2Strength
If filler material is used to weld or solder nitinol to stainless steel, then the components can be joined, but this creates a weak point in the bond and deteriorates the thermal properties of nitinol
Solution Approach 1:
The patent extracts the problematic filler material from the joining process entirely. Instead of using filler materials that compromise thermal properties and create weak points, the invention uses a pure mechanical interference fit achieved through stretching and recovery of the nitinol wire, eliminating the need for any filler substance and preserving nitinol's thermal characteristics.
Solution Approach 2:
The patent replaces the thermal/mechanical bonding process (welding or soldering with filler) with a purely mechanical interference fit system. The stretched nitinol wire is inserted through the receiver opening, and upon elastic recovery, creates a secure mechanical lock that eliminates the need for thermal processes and filler materials, thereby preserving thermal properties.
3Ease of operation
If the nitinol wire is stretched to reduce cross-sectional dimension for fitting, then it can be inserted through the opening, but the wire must be altered from its natural state
Solution Approach 1:
The patent applies dynamics by utilizing the time-dependent elastic deformation and recovery of the nitinol wire. The wire is dynamically stretched to a reduced cross-sectional dimension for insertion, then dynamically recovers to its original dimensions upon release, creating the interference fit. This dynamic approach allows easy fitting while maintaining the wire's compositional stability through its inherent superelastic properties.
Solution Approach 2:
The patent temporarily changes the dimensional parameter of the nitinol wire through stretching, allowing it to pass through the receiver opening. After insertion, the wire naturally recovers its original dimensions, creating a secure fit. This temporary parameter change facilitates ease of operation while the wire's material composition remains stable throughout the process.
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 securely couples nitinol components to other medical device components without creating weak points, maintaining the thermal properties of nitinol and ensuring a strong, reliable bond, suitable for various medical devices.
Implementation Method 1
Nitinol has super-elastic properties that give it high flexibility, shape recoverability... altering the first medical device component from a natural state to an altered state, by reducing a cross-sectional dimension of the first medical device... allowing the second portions of the first medical device component to revert back to the natural state
Data Source
AI summary
A method for coupling a first medical device component to a second medical device component comprising altering the first medical device component from a natural state to an altered state, by reducing a cross-sectional dimension of the first medical device, fitting a first portion of the first medical device component in the altered state into a first opening of the second medical device component, wherein the first medical device component includes second portions not within the first opening of the second medical device component, and allowing the second portions of the first medical device component to revert back to the natural state.