Loop Catheter Activation Wire Coupling for Dissimilar Metal Joining
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Solution Overview
Problem
Existing catheters face challenges in creating a robust connection between dissimilar materials, such as stainless steel and nitinol, for the activation of distal features like loop radii adjustments, due to issues like brittle intermetallic formation, which affects the reliability of crimping or brazing methods.
Innovation Solution
A wire coupling system using a sleeve made of nickel superalloy, such as Inconel 600, is laser-welded to both stainless steel and nitinol wires, facilitating a strong and reliable connection by avoiding intermetallic formation and accommodating different wire diameters and compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If crimping or brazing methods are used to connect dissimilar wires (stainless steel and nitinol), then the connection process is simple, but brittle intermetallic formation occurs reducing reliability
Solution Approach 1:
A nickel superalloy sleeve (Inconel 600) is introduced as an intermediary component between the stainless steel activation wire and the nitinol loop wire. The sleeve is laser-welded to both wires, creating a reliable connection without direct contact between dissimilar metals. This mediator prevents brittle intermetallic formation while maintaining manufacturing simplicity through a standardized three-component assembly process.
2Device complexity
If direct connection between dissimilar materials is made, then device complexity is reduced, but connection strength decreases due to intermetallic formation
Solution Approach 1:
The connection assembly utilizes a composite structure comprising three different materials: stainless steel activation wire, nickel superalloy sleeve (Inconel 600), and nitinol loop wire. Each material is selected for its specific properties - the nickel superalloy sleeve provides excellent laser weldability and compatibility with both stainless steel and nitinol, creating a strong tri-material connection that overcomes the weaknesses of direct dissimilar metal joining.
3Strength
If laser welding is used to connect dissimilar wires, then connection strength is improved, but manufacturing complexity increases
Solution Approach 1:
The nickel superalloy sleeve (Inconel 600) possesses inherent properties that facilitate the manufacturing process - it is self-compatible with laser welding to both stainless steel and nitinol materials. The sleeve's material characteristics enable reliable laser weld formation without requiring additional process steps, specialized equipment, or complex manufacturing procedures, making the laser welding process straightforward and repeatable.
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 solution enables reliable and robust attachment of dissimilar wires, allowing for precise manipulation of catheter loop radii and positions, enhancing the stability and effectiveness of catheter features during medical procedures.
Implementation Method 1
a laser weld affixing the sleeve to both the first wire and alongside the second wire
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Disclosed is a coupling for use in a looped medical device, such as a loop catheter. A sleeve is fitted onto a distal portion of an activation wire and a shape-memory wire is positioned alongside the sleeved activation wire. The sleeve is welded onto the activation wire to hold the sleeve onto the activation wire and is also welded onto the shape-memory wire that is positioned alongside the activation wire, thereby affixing the activation wire to the shape-memory wire. Also disclosed is an activation wire for use in a catheter. The activation wire includes a proximal section, and a distal section having at least a partial loop. The activation wire includes a connection section on the distal section, where the connection section is linear, and where the external surface of the connection section has a higher coefficient of friction than at least some of the remaining portion of the actuation wire that is housed within the catheter shaft.