Welded Nitinol Guide Wire Core Segments
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Solution Overview
Problem
Conventional guide wires for angioplasty and other intravascular procedures face challenges in balancing column strength and flexibility, with difficulties in joining stainless steel and nitinol materials due to welding issues, leading to potential buckling or damage to blood vessels.
Innovation Solution
A multi-segment guide wire design featuring a high-strength stainless steel proximal core and a flexible nitinol distal core, connected via a nickel transition piece using advanced welding methods like friction or laser welding, ensuring a strong and flexible connection without compromising the properties of nitinol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an external connecting tube is used to join stainless steel proximal core to nitinol distal core, then the connection strength is improved, but the guide wire profile increases and obstructs catheter elements
Solution Approach 1:
The invention removes the external connecting tube from the guide wire structure and instead directly welds the nitinol distal core to the stainless steel proximal core. This extraction of the tube eliminates the profile obstruction problem while maintaining connection strength through direct welding of the core materials.
Solution Approach 2:
The invention introduces a specialized welding process as an intermediary method to directly join the dissimilar metals (stainless steel and nitinol) without requiring an external connecting tube. This welding intermediary enables direct fusion of the two materials, achieving both strong connection and minimal profile.
2Device complexity
If direct welding of nitinol to stainless steel is attempted, then the guide wire profile is minimized, but welding deficiencies and cracking occur at the interface
Solution Approach 1:
The invention modifies the welding parameters specifically for joining nitinol to stainless steel, controlling heat input, welding speed, and thermal cycle to prevent interface cracking and welding deficiencies. By optimizing these parameters, direct welding achieves both minimal profile and high reliability.
Solution Approach 2:
The invention applies localized welding techniques that concentrate the joining process at the interface between nitinol and stainless steel, controlling heat distribution to prevent cracking while achieving strong bonds. The welding parameters are specifically tailored for the local conditions at the material interface.
3Ease of operation
If the distal core is made of flexible nitinol material, then flexibility is improved, but column strength decreases leading to buckling risk
Solution Approach 1:
The invention divides the guide wire core into two distinct segments: a proximal stainless steel core providing column strength and pushability, and a distal nitinol core providing flexibility and shapeability. This segmentation allows each material to perform its optimal function without compromising the other.
Solution Approach 2:
The invention creates a composite structure by joining dissimilar materials (stainless steel and nitinol) with different mechanical properties. The stainless steel segment provides high strength and stiffness for pushing through the vasculature, while the nitinol segment provides flexibility and shape memory for navigating tortuous anatomy.
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 solution provides a guide wire with enhanced column strength and flexibility, minimizing the risk of buckling or damaging blood vessels, while maintaining the beneficial properties of nitinol, and allowing for smooth catheter movement during procedures.
Implementation Method 1
connected via a nickel transition piece using advanced welding methods like friction or laser welding
Implementation Method 2
connected via a nickel transition piece using advanced welding methods like friction or laser welding
Implementation Method 3
a flexible nitinol distal core
Data Source
Figure 1~2C
Figure 3~4
Figure 5~6
AI summary
An intravascular guide wire having two core materials joined together without the use of a connector tube or sleeve, the core materials being stainless steel and psuedoelastic metal alloy, nitinol. The core materials are joined to each other through an intermediate transition piece made essentially of nickel, which is welded on either side to the two core materials. In a multi-segment intravascular guide wire, discrete, high modulus and medium modulus core portions of different materials are welded to a shapeable, low modulus distal core portion made of a third material having a flattened, shapeable section at a most distal end that is not welded to but made from the distal core portion, so the flattened, shapeable section can be deformed to create a steerable tip. Processes such as simultaneous resistance and friction welding can be used to join the core portions.