Nitinol Component Coupling Through Shape-Recovery 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 and deteriorate thermal properties when filler materials are used.
Innovation Solution
A method involving altering the nitinol component by reducing its cross-sectional dimension through stretching, allowing it to fit into an opening of another component, and then allowing it to revert back to its original state, thereby securely coupling without the need for fillers or heat exposure, using receivers that accommodate the nitinol wire in its altered state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitinol is bonded to dissimilar materials using conventional methods (adhesive bonding, welding, crimping, swaging), then coupling is achieved, but the hard oxide outer layer of nitinol limits bonding and creates weak points
Solution Approach 1:
The patent applies parameter changes by utilizing the temperature-dependent properties of nitinol. The nitinol component is heated to austenite transformation temperature or above, changing its physical state to enable elastic deformation. This allows the component to be compressed to a smaller cross-sectional dimension for insertion through an opening, then upon cooling, it reverts to its original shape, creating a secure interference fit without fillers or heat exposure to dissimilar materials.
2Strength
If filler material is used to weld or solder nitinol to stainless steel, then coupling is achieved, but it creates a weak point in the bond and deteriorates thermal properties
Solution Approach 1:
The patent extracts the harmful filler material from the coupling process entirely. Instead of using filler materials that create weak points and deteriorate thermal properties, the invention relies on the elastic deformation and shape memory characteristics of nitinol to create a direct mechanical interference fit between the nitinol component and the receiving component, eliminating the need for any intermediate bonding materials.
Solution Approach 2:
The patent replaces thermal bonding processes (welding, soldering) with a mechanical coupling mechanism. The nitinol component's elastic deformation and shape recovery provide the coupling force through mechanical interference fit, substituting thermal fields with mechanical fields to achieve the bonding function without heat exposure to dissimilar materials.
3Ease of operation
If the cross-sectional dimension of nitinol is reduced to fit through an opening, then coupling becomes possible, but the component must be altered from its natural state
Solution Approach 1:
The patent applies dynamics by making the nitinol component's dimensions changeable through temperature control. The component transitions between different physical states (austenite and martensite) based on temperature, allowing it to dynamically adjust its cross-sectional dimension. When heated, it becomes elastic and can be compressed; when cooled, it reverts to its original shape, providing both ease of fitting and dimensional stability in its final state.
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 using fillers or heat, maintaining the shape recovery characteristics of nitinol and providing a strong, reliable bond that inhibits rotation and translation, suitable for various medical devices.
Implementation Method 1
Nitinol has super-elastic properties that give it high flexibility, shape recoverability, kink resistance, high fatigue strength, corrosion resistance, and heat resistance
Implementation Method 2
The altering step may include stretching the wire so that a diameter of the wire is less than or equal to a width of the first opening
Data Source
AI summary
A method for coupling a first medical device component to a second medical device component includes 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. The method further includes fitting a first portion of the first medical device component in the altered state into a first opening of the second medical device component. The first medical device component includes second portions not within the first opening of the second medical device component. The method further includes allowing the second portions of the first medical device component to revert back to the natural state.