Variable-Hardness Catheter Structure for Kink Resistance
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Solution Overview
Problem
Catheters inserted into complex body tissues and organs are prone to kinks and breakages due to stress concentration at the boundary between sections with and without a metal layer, leading to rigidity gaps.
Innovation Solution
A catheter design with varying resin hardness regions, including a first region with high hardness, a second region with lower hardness, and optionally a third region with even higher hardness, to gradually increase rigidity from the distal end to the proximal end, reducing rigidity gaps and stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal layer is disposed on the outer periphery of the inner layer to increase catheter rigidity, then the catheter can maintain its shape and provide torquability, but a rigidity gap occurs at the boundary between sections with and without the metal layer, causing stress concentration and increasing the likelihood of kinks and breakages
Solution Approach 1:
The outer layer is designed with different hardness regions: a first region with higher hardness that covers the metal layer to provide rigidity, and a second region with lower hardness at the boundary area to reduce stress concentration. This local variation in material properties eliminates the rigidity gap while maintaining overall catheter strength and torquability.
Solution Approach 2:
The hardness parameter of the outer layer resin is changed across different regions. By controlling the resin composition and curing conditions, the patent creates a gradient in hardness from the first region (higher hardness) to the second region (lower hardness), which smoothly transitions the rigidity profile and prevents stress concentration at the metal layer boundary.
2Device complexity
If the catheter is made with uniform rigidity throughout, then the structure is simple and easy to manufacture, but the catheter cannot navigate bent and constricted blood vessels without risking kinks and breakages
Solution Approach 1:
The catheter is segmented into different functional regions along its length. The outer layer is divided into a first region with higher hardness for rigidity and a second region with lower hardness for flexibility. This segmentation allows the catheter to have both rigid sections for torquability and flexible sections for navigating bent vessels, improving deliverability while maintaining structural integrity.
Solution Approach 2:
The catheter exhibits dynamic mechanical properties through the varying hardness of the outer layer. The lower hardness second region allows the catheter to dynamically adapt to bent and constricted blood vessel geometries during insertion, while the higher hardness first region maintains torquability. This dynamic response enables safe navigation through complex vascular paths.
Data Source
AI summary
This catheter includes an outer layer formed of a resin, and an inner member covered with the outer layer. The distal end of the inner member is located proximally of the distal end of the outer layer. The outer layer has a first region extending from the distal end of the outer layer to the distal end of the inner member, and a second region which is positioned proximally of the first region and covers the inner member. The resin which forms the second region of the outer layer has a lower hardness than the resin which forms the first region.