Stranded Wire Stent Design for Fatigue and Profile Trade-offs
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Solution Overview
Problem
Existing stents face challenges in achieving a lower delivery profile while providing sufficient support to diseased vessels and maintaining a longer fatigue life, as they often result in shorter fatigue life due to smaller radii or diameters, leading to reduced radial force and increased strut numbers.
Innovation Solution
A stent wire comprising a plurality of filaments twisted into a bundle and bent into a pattern with substantially straight sections separated by bends, spirally wound about a central axis, with at least one filament displaced and spaced from adjacent filaments, allowing for optimized tensile strength through heat-treatment and stress relief at the apex of struts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a smaller radius is used to lower the overall profile of the stent, then the delivery profile is reduced, but the fatigue life becomes shorter
Solution Approach 1:
The stent wire is segmented into multiple filaments (e.g., 7 filaments) twisted together to form a stranded wire structure. This segmentation allows each filament to independently withstand stress, preventing catastrophic failure and extending fatigue life while maintaining a compact overall profile.
Solution Approach 2:
The stent is constructed as a composite structure combining multiple metal filaments twisted into a stranded wire, creating a composite material system that provides both the required mechanical strength and extended fatigue resistance while maintaining a low delivery profile.
2Volume of moving object
If a smaller diameter wire is used to lower the profile of the stent, then the delivery profile is reduced, but the radial force decreases
Solution Approach 1:
The wire is divided into multiple filaments that collectively provide the necessary radial force. While each individual filament is thin, their combined cross-sectional area and distributed structure enable the stent to exert sufficient radial force against the vessel wall while maintaining a compact profile.
Solution Approach 2:
The radial force is enhanced by utilizing the helical twist geometry of the stranded wire. The twisted configuration of multiple filaments creates a three-dimensional structure that converts axial compression into radial expansion force, providing adequate radial support despite using thinner individual filaments.
3Force
If the number of struts is increased to provide more support, then the radial force increases, but the profile becomes higher
Solution Approach 1:
The invention changes the physical parameters of the wire by using multiple twisted filaments instead of a solid wire. This parameter change allows the stent to achieve the required radial force through the combined strength of multiple filaments while maintaining a smaller overall profile, avoiding the need to increase the number of struts.
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 enables a stent with a lower delivery profile and extended fatigue life by distributing stress across a longer section and multiple planes, reducing apex stress and enhancing radial force without fatigue or weakening, even in corrosive environments.
Implementation Method 1
a stent wire comprising a plurality of filaments twisted into a bundle having a helix
Implementation Method 2
The tensile strength of the strands may be optimized by heat-treatment to give the most favorable characteristics so as to relieve strain particularly at the apex of the adjoining struts
Data Source
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AI summary
A stent including a stent wire comprising a plurality of filaments twisted into a bundle having a helix, the stent wire being bent into a pattern having a plurality of substantially straight wire sections separated by a plurality of bends. The pattern of the stent wire is spirally wound about a central axis in the same direction as the helix formed by the plurality of filaments. The each of the filaments in a bend have a cylindrical cross-section where at least one of the plurality of filaments is displaced and spaced from an immediately adjacent filament in the bend.