Nitinol Wire Coupling by Interference Fit Without Thermal Bonding
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Solution Overview
Problem
Existing methods for bonding nitinol components in medical devices are hindered by the hard oxide layer, leading to weak bonds and deterioration of thermal properties, particularly when joining nitinol to stainless steel.
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 shape, creating a secure interference fit without adhesives or heat exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitinol is joined to stainless steel using welding or soldering with filler material, then the components can be coupled together, but the bond strength is reduced and thermal properties deteriorate
Solution Approach 1:
The patent replaces thermal joining methods (welding, soldering) with a mechanical interference fit system. The nitinol wire is stretched to reduce its diameter, inserted through the receiver component, and then allowed to recover its original diameter, creating a mechanical lock that eliminates the need for filler materials and thermal processes, thereby preserving thermal properties and achieving strong bonds.
Solution Approach 2:
The patent utilizes the parameter change of nitinol's diameter through stretching and recovery. The wire diameter is temporarily reduced to enable insertion, then returns to its original size to create the interference fit. This dynamic parameter change allows for strong mechanical coupling without compromising thermal characteristics.
2Strength
If adhesive bonding is used to join nitinol components, then the components can be coupled, but the hard oxide layer prevents effective bonding
Solution Approach 1:
The patent replaces chemical adhesive bonding with a mechanical interference fit system. By stretching the nitinol wire to reduce its diameter and then allowing it to recover, the invention creates a mechanical lock that does not depend on the surface oxide layer, thereby achieving strong bonds without the complexities of surface preparation and adhesive application.
3Length of moving object
If the nitinol wire diameter is reduced to fit through the receiver opening, then the wire can be inserted, but the wire must be stretched which may affect its properties
Solution Approach 1:
The patent deliberately changes the wire's diameter parameter through stretching to enable insertion, then allows the parameter to return to its original value through elastic recovery. This controlled parameter change exploits nitinol's superelastic properties to achieve insertability while preserving the wire's mechanical properties.
Solution Approach 2:
The nitinol wire's own superelastic properties are utilized to perform the size reduction and recovery functions. The material's inherent ability to stretch and recover eliminates the need for external processing or modification, maintaining wire properties while enabling insertion.
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 method enables robust coupling of nitinol components to other materials, maintaining shape recovery characteristics and preventing rotation, while avoiding weak points and thermal deterioration.
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
Implementation Method 2
allowing the second portions of the first medical device component to revert back to the natural state
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 2D
AI summary
A medical device (50) comprising a nitinol wire (100") defining a loop (54), a first strand (52), and a second strand (53), each of the first strand (52) and the second strand (53) extending proximal to the loop (54); and a receiving component (60') coupled to the first strand (52) and the second strand (53), wherein the receiving component (60') includes a first opening (61'), and a portion of the first strand (52) extends through the first opening (61'), wherein a diameter of the portion of the first strand (52) is less than a diameter of a remaining portion of the first strand (52); wherein the receiving component (60') further includes a second opening (62), and a portion of the second strand (53) extends through the second opening (62), wherein a diameter of the portion of the second strand (53) is less than a diameter of a remaining portion of the second strand (53).