Polymer Scaffolds with Modified Crowns for Crush Recovery
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Solution Overview
Problem
Current polymer scaffolds for peripheral blood vessels face challenges in maintaining radial strength and stiffness while avoiding residual outward forces, and they are prone to fracture and cracking under external loads, making them unsuitable for long-term use in peripheral arteries.
Innovation Solution
A crush-recoverable polymer scaffold design with modified crown structures and link elements that reduce the inner radius of crowns and introduce pre-designed fracture points, allowing for high crush recovery and radial stiffness without sacrificing structural integrity, and incorporating radiopaque markers for improved visibility during deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polymer scaffolds are designed with high radial strength and stiffness, then they can maintain vessel patency, but they become prone to fracture and cracking under external loads
Solution Approach 1:
The scaffold is divided into multiple struts and links forming a grid pattern, where each element can independently absorb stress. The struts are connected by links that can flex and deform, preventing stress concentration that would lead to fracture while maintaining overall radial strength through the distributed structure.
Solution Approach 2:
Different regions of the scaffold have different structural properties - the struts provide radial strength while the links provide flexibility. The crown structures at junctions have modified geometries with larger inner radii to reduce stress concentration, while the connecting links have smaller cross-sections to allow flexing and prevent fracture propagation.
2Volume of moving object
If polymer scaffolds are made with thinner walls to reduce profile, then delivery is easier, but radial strength and stiffness are compromised
Solution Approach 1:
The scaffold employs curved crown structures at the junctions of struts and links. These curved geometries with optimized inner radii distribute stress more effectively than sharp corners, allowing thinner wall sections to maintain the same radial stiffness. The curvature prevents stress concentration that would otherwise require thicker walls to compensate.
Solution Approach 2:
The scaffold combines polymer material with a specific geometric composite structure - the grid pattern of struts and links creates an effective composite where the overall structure provides radial stiffness even though individual wall sections are thin. The geometric configuration compensates for the reduced material thickness.
3Force
If polymer scaffolds are designed for crush recovery, then they can withstand external compression, but they may not maintain structural integrity for long-term use
Solution Approach 1:
The scaffold is designed with dynamic characteristics - the links can flex and the structure can deform under compressive loads to achieve crush recovery. However, the overall grid pattern and crown structures maintain structural integrity by distributing stresses, allowing the scaffold to withstand both acute compression events and long-term cyclic loading without failure.
Solution Approach 2:
The crown structures are designed with larger inner radii and reinforced geometries before the scaffold is deployed, creating stress distribution patterns that prevent fracture initiation. This pre-engineered stress distribution allows the scaffold to recover from crush events while maintaining the structural integrity needed for long-term vessel support.
Data Source
AI summary
A medical device includes a polymer scaffold crimped to a catheter having an expansion balloon. The scaffold, after being deployed by the balloon, provides a crush recovery of about 90% after the diameter of the scaffold has been pinched or crushed by 50%. The scaffold also has a reduced crimped profile and a modification of the scaffold's ring structure at the crowns that contributes to the reduced crimped profile.