Intravascular Stent Fatigue Relief Dimples
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Solution Overview
Problem
Polymeric stents face challenges with fatigue failure due to cyclic loads and stress concentrations, particularly in dynamic environments like curved arteries, leading to mechanical instability and potential failure.
Innovation Solution
The design incorporates a series of radially expandable cylindrical rings with interconnecting links that provide flexibility and stability, featuring serpentine or undulating shapes with U-shaped elements, Y-shaped members, and relief dimples to distribute stress and prevent warping, ensuring improved fatigue performance and maintaining patency of blood vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polymeric stent is used to maintain vascular patency, then the stent provides flexibility for delivery through tortuous vessels, but the stent is susceptible to fatigue failure due to cyclic loads and stress concentrations
Solution Approach 1:
The patent applies local quality by introducing relief dimples at specific high-stress locations (inner bends and link connections) of the stent structure. These localized modifications concentrate stress relief features exactly where fatigue failures are most likely to occur, rather than uniformly modifying the entire stent. This allows the stent to maintain overall flexibility while providing targeted fatigue resistance at critical points.
Solution Approach 2:
The patent employs a composite structural approach by combining polymeric material with strategically placed relief dimples that create a hybrid stress distribution pattern. The relief dimples act as stress redistribution features within the polymeric matrix, effectively creating a composite-like behavior that enhances fatigue performance while preserving the inherent flexibility of the polymeric material.
2Strength
If the stent structure is made more rigid to resist radial compressive forces, then radial strength is improved, but longitudinal flexibility is reduced
Solution Approach 1:
The relief dimples are strategically positioned only at critical stress points (inner bends and link connections) rather than uniformly across the entire stent structure. This localized modification allows the stent to maintain its overall flexible configuration while providing targeted reinforcement exactly where radial compressive forces and cyclic loading create the highest stress concentrations.
Solution Approach 2:
The stent is divided into distinct structural elements (cylindrical rings, links, bends) with relief dimples applied selectively to specific segments. This segmentation allows different parts of the stent to have different mechanical properties - the relief dimpled areas provide enhanced radial strength while the undimpled areas maintain flexibility for longitudinal movement and vessel conformation.
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 stent achieves enhanced flexibility and stability, minimizing recoil and maintaining vascular patency by distributing stress evenly, thus reducing the risk of mechanical failure and ensuring effective deployment and functionality within the body.
Implementation Method 1
relief dimples to distribute stress and prevent warping
Implementation Method 2
The cylindrical rings are configured to provide flexibility to the stent
Implementation Method 3
Interconnecting elements or links extending between adjacent cylindrical rings provide increased stability and prevent warping of the stent upon the expansion thereof
Data Source
AI summary
The 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 comprised of a link and a U-shaped member has relief dimples formed in the curved portion of a valley to reduce localized stress and thereby reduce fatigue failure that can lead to link structure failure.