Nitinol Component Coupling by Shape Recovery Interference Fit
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Solution Overview
Problem
Existing methods for coupling nitinol components to dissimilar materials in medical devices face challenges due to the hard oxide layer of nitinol, which limits bonding and can deteriorate its thermal properties, often requiring filler materials that create weak points in the bond.
Innovation Solution
A method involving altering the cross-sectional dimension of a nitinol component by stretching it to fit into an opening of a receiver component, allowing it to revert to its original dimension upon removal of the force, thereby securely coupling without adhesives or heat exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitinol is bonded to dissimilar materials using traditional methods (adhesive bonding, welding, crimping, or swaging), then coupling is achieved, but the hard oxide outer layer of nitinol limits bonding and creates weak points requiring filler materials that deteriorate thermal properties
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transformation properties of nitinol (austenite to martensite phase change) to enable coupling. By controlling temperature and stress parameters, the nitinol wire transitions between phases, allowing it to be inserted in a compliant state and then recover its original shape to create a secure mechanical interlock without fillers or adhesives, thereby maintaining thermal properties and bond integrity
Solution Approach 2:
The patent replaces traditional mechanical coupling methods (welding, adhesives, filler materials) with a shape memory mechanical interlock system. The nitinol wire's superelasticity and shape memory effects provide the coupling mechanism through controlled deformation and recovery, eliminating the need for filler materials that create weak points and preserve thermal conductivity
2Strength
If filler material is used to weld or solder nitinol to stainless steel, then coupling is achieved, but weak points are created in the bond and thermal properties deteriorate
Solution Approach 1:
The patent extracts and eliminates filler materials from the coupling process entirely. By using nitinol's intrinsic shape memory properties, the invention achieves direct mechanical coupling between dissimilar materials without intermediate filler layers, removing the source of weak points and thermal property deterioration while maintaining strong bonds
Solution Approach 2:
The patent uses the nitinol wire itself as an intermediary that actively participates in the coupling mechanism through phase transformation. Rather than using passive filler materials, the nitinol undergoes controlled phase changes to create a mechanical interlock that directly couples dissimilar materials without requiring separate filler components
3Ease of operation
If the cross-sectional dimension of nitinol is reduced to fit into openings, then coupling is enabled, but the natural state dimensions prevent entry
Solution Approach 1:
The patent applies dynamics by making the nitinol wire's cross-sectional dimension variable through phase transformation. The wire transitions from a rigid austenite phase with larger dimensions to a more compliant martensite phase with reduced effective stiffness, enabling insertion into openings, then transforms back to austenite to achieve a secure interference fit
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 enables robust and secure coupling of nitinol components to other materials, maintaining the material's properties and avoiding weak points in the bond, while allowing for interference fit and rotational stability.
Implementation Method 1
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... applying a force to the medical device component in a direction transverse to the direction of the cross-sectional dimension
Implementation Method 2
allowing the second portions of the first medical device component to revert back to the natural state... allowing the cross-sectional dimension of the first portion of the first medical device component to increase to a dimension of the opening
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.