Customized Stent Alloy Balloon-Expandable Deployment
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Solution Overview
Problem
Vascular stents face challenges in achieving a balance of mechanical properties such as high modulus of elasticity, low yield point, high work hardening rate, and biocompatibility, often requiring trade-offs in material selection, which can lead to vessel trauma and restenosis due to over-expansion and recoil issues during deployment.
Innovation Solution
A customized alloy with a high work hardening rate, high modulus of elasticity, and low yield point is developed for balloon-expandable stents, allowing for significant plastic deformation with minimal recoil, using materials like tantalum, niobium, and cobalt-based alloys, and varying strain hardening exponents to optimize stent expansion and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength stent materials are used to provide radial support, then strength and endurance are improved, but vessel trauma and restenosis occur due to over-expansion and recoil
Solution Approach 1:
The patent applies parameter changes by carefully controlling the mechanical properties of the stent material, specifically the yield point and work hardening rate. By selecting materials with a yield point between 200-500 MPa and a work hardening rate between 0.1-1.0, the stent achieves optimal balance between strength and trauma prevention. This parameter optimization allows the stent to provide sufficient radial support while minimizing over-expansion and recoil that cause vessel trauma.
Solution Approach 2:
The patent employs composite materials by combining different metal alloys with complementary properties. The stent may use coatings or layered structures that combine the strength of high-modulus materials with the ductility and biocompatibility of other materials. This composite approach enables the stent to achieve both high radial support strength and reduced vessel trauma by leveraging the advantages of multiple materials.
2Strength
If high modulus of elasticity materials are used to provide radial support, then strength is improved, but flexibility for navigating tortuous anatomy is reduced
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the modulus of elasticity within a specific range (50-200 GPa) rather than using maximum strength materials. This moderate modulus range provides sufficient radial support while maintaining adequate flexibility for navigation through tortuous vascular anatomy. The work hardening rate parameter is also optimized to control the material's response to deformation during navigation and deployment.
3Object-affected harmful factors
If low yield point materials are used to reduce recoil, then vessel trauma is reduced, but radial support strength is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the yield point within the range of 200-500 MPa and the work hardening rate within 0.1-1.0. This optimized parameter combination ensures the stent has sufficient radial support strength while exhibiting minimal recoil and over-expansion. The work hardening rate parameter is critical in maintaining strength during deployment while preventing excessive spring-back that would cause trauma.
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 customized alloy enables precise sizing and reduced trauma to the vessel wall by minimizing recoil and over-expansion, providing enhanced radial support and biocompatibility, while maintaining flexibility for tortuous anatomy navigation.
Implementation Method 1
a radially-expandable stent must undergo significant plastic deformation when being expanded into its deployed state
Implementation Method 2
the stent may need to be over expanded in order to compensate for metallurgical recoil, which occurs in high strength stents
Data Source
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AI summary
A balloon-expandable stent formed from a customized alloy formulation. The stent alloy has a either a high, variable or no work hardening rate, very high modulus of elasticity (Young's modulus), and a low yield point. A stent constructed of a material with this combination of properties undergoes significant plastic deformation upon deployment in vivo to its implantation diameter and exhibits minimum recoil for better sizing. The plastic deformation also raises the subsequent yield point of the stent material resulting in a stronger stent upon implantation that is more resistant to vascular loading.