Variable Curvature Stent Limb Design for Fatigue Life
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Solution Overview
Problem
Self-expanding stents face challenges with permanent deformation and limited fatigue life due to uneven strain distribution and increased radial force during compression and expansion, making them difficult to compress to smaller diameters and deploy accurately.
Innovation Solution
A variable curvature stent limb design with non-constant radii of curvature in opposite directions, allowing for more even strain distribution and enhanced compressibility, compatible with low-profile delivery devices, and made from materials like superelastic alloys for improved fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If self-expanding stents are compressed to smaller diameters for delivery, then they can be loaded into catheters, but the radial force increases making compression progressively more difficult
Solution Approach 1:
The stent employs an S-shaped curvature design with variable radius of curvature along its length. The curvature is designed such that the radius varies to create regions of different flexibility, allowing the stent to compress more easily to smaller diameters while maintaining structural integrity. This curvature design redistributes the radial force more favorably during compression.
Solution Approach 2:
The stent features non-uniform curvature with different regions having different radii of curvature. This creates local variations in mechanical properties, with some regions being more flexible than others. This local quality variation allows different parts of the stent to deform differently during compression, reducing peak radial forces and enabling compression to smaller delivery diameters.
2Length of moving object
If self-expanding stents are compressed to smaller diameters, then they can be delivered through catheters, but the strain increases causing permanent deformation or failure
Solution Approach 1:
The S-shaped curvature with variable radius distributes the mechanical strain more evenly throughout the stent structure during compression. By optimizing the curvature profile, the design prevents concentration of strain at specific locations, thereby reducing the risk of permanent deformation or material failure while enabling compression to smaller diameters.
Solution Approach 2:
Different regions of the stent are designed with different curvature radii to create local variations in strain distribution. This ensures that no single region experiences excessive strain during compression, protecting the overall structural integrity of the stent while allowing delivery through catheters.
3Force
If self-expanding stents have high radial force, then they provide good vessel support, but the friction increases making release from catheter difficult
Solution Approach 1:
The stent design creates a distinction between delivery-state properties and deployed-state properties. During delivery, the variable curvature allows easier compression with reduced peak radial forces, lowering friction with the catheter. Upon deployment, the stent expands to its configured S-shape that provides adequate radial support force for vessel engagement, thus resolving the contradiction between delivery ease and deployment support.
4Reliability
If current stent designs are used, then they can be deployed in vessels, but they have short fatigue life due to uneven strain distribution
Solution Approach 1:
The S-shaped curvature with specifically designed variable radius along the stent length creates a more uniform distribution of strain during the compression-expansion cycling that occurs with normal blood flow. This uniform strain distribution prevents stress concentration at specific locations, thereby extending the fatigue life of the stent while maintaining adequate structural strength.
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 variable curvature stent design enhances compressibility, reduces frictional forces during deployment, and extends fatigue life by evenly distributing strain, enabling use across a range of vessel diameters with improved sealing and support characteristics.
Implementation Method 1
the first radius of curvature is non-constant. The variably curvature stent limb also possesses a second variably curved region
Implementation Method 2
made from materials like superelastic alloys for improved fatigue life
Data Source
AI summary
A variable curvature stent limb is disclosed herein. A stent derived from a plurality of these variable curvature stent limbs may be highly compressible, such that it is compatible with a low-profile delivery device. This stent may be useful over a wider range of body vessel diameters and may possess a greater fatigue life, since this stent may provide a more controlled constant radial force.