Polymer Stent Y-Link Structure for Flexibility and Fatigue Life
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Solution Overview
Problem
Existing stents face challenges in maintaining radial strength, flexibility, and fatigue resistance due to cyclic loading and implantation in dynamic environments, particularly when made from polymers that are prone to brittleness and mechanical failure.
Innovation Solution
A polymer stent design featuring radially expandable cylindrical rings interconnected by links, with strategically positioned undulating patterns and Y-shaped members to enhance flexibility and fatigue performance, while maintaining radial strength and biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polymer stent is made flexible to facilitate delivery through tortuous vessels, then longitudinal flexibility is improved, but fatigue resistance deteriorates due to cyclic loading in the dynamic implantation environment
Solution Approach 1:
The stent is divided into multiple cylindrical rings that are relatively independent in their ability to expand and flex. This segmentation allows each ring to independently accommodate cyclic loading while maintaining overall stent flexibility, resolving the contradiction between flexibility and fatigue resistance
Solution Approach 2:
Different structural features are applied at different locations: undulating patterns are positioned at specific areas to enhance flexibility where needed, while Y-shaped members are strategically placed to improve fatigue performance in critical regions subjected to concentrated cyclical loads
2Strength
If the stent structure is made rigid to maintain radial strength and resist recoil forces, then radial strength is improved, but longitudinal flexibility deteriorates, preventing proper maneuvering through tortuous paths
Solution Approach 1:
The stent is segmented into multiple cylindrical rings connected by interconnecting elements. This segmentation allows the stent to exhibit rigid behavior radially (resisting compression) while maintaining flexibility longitudinally (allowing bending), as each ring can independently resist radial forces while the connections between rings permit longitudinal flexure
Solution Approach 2:
The stent structure is designed to exhibit dynamic mechanical behavior: the cylindrical rings and interconnecting elements are configured to allow controlled movement and flexing in the longitudinal direction while maintaining radial stiffness, enabling the stent to adapt its mechanical properties based on the direction of applied forces
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 design improves fatigue resistance and flexibility, allowing safe delivery and effective deployment in tortuous vessels, with enhanced structural integrity and reduced mechanical failure risk.
Implementation Method 1
The stent of the invention generally includes a plurality of radially expandable cylindrical elements or rings which are relatively independent in their ability to expand and to flex relatively to one another
Implementation Method 2
Radial strength, which is the ability of a stent to resist radial compressive forces, is due to strength and rigidity around a circumferential direction of the stent
Data Source
AI summary
This invention is directed to an expandable stent for implantation in a body lumen, such as an artery, and a method for making it from a single length of tubing. The stent consists of a plurality of radially expandable cylindrical elements generally aligned on a common axis and interconnected by one or more links. A Y-shaped member is comprised of a U-shaped member and a link having a curved portion and a straight portion to improve the flexibility and thereby improve the fatigue performance of the Y-link junction.