Bioresorbable Stent Struts with Shape Memory Alloy Reinforcement
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Solution Overview
Problem
Bioresorbable polymeric stents face challenges with brittle fracture when expanding or collapsing, limiting their ability to securely expand and maintain position within vessels due to inherent mechanical weaknesses, which complicates their deployment and effectiveness in treating bifurcation lesions.
Innovation Solution
A dip-coating process is used to create polymeric substrates with high molecular weight and controlled crystallinity, allowing for the formation of stents with enhanced radial strength and ductility, enabling the enlargement of open cells without fracturing, and incorporating multiple layers for improved mechanical properties and drug delivery capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymeric stent is expanded for placement within a vessel, then the stent can maintain position and treat the lesion, but the stent may suffer from brittle fracture and mechanical failure due to inherent material weakness
Solution Approach 1:
The patent employs composite material structures by combining polymeric stent material with metallic reinforcement elements (such as shape memory alloy wires or mesh). This composite approach allows the stent to maintain the biocompatibility and flexibility of polymers while gaining the strength and fracture resistance of metals, thereby resolving the contradiction between reliability and material strength.
Solution Approach 2:
The patent utilizes parameter changes by transforming the mechanical properties of the stent material through phase transitions. Shape memory alloys are employed that can transition between martensitic (soft, flexible) and austenitic (strong, rigid) phases, allowing the stent to be compressed for delivery and then strengthened upon expansion, thus improving both reliability and strength simultaneously.
2Adaptability or versatility
If open cells along the stent are enlarged to allow greater flow between main vessel and side branch, then blood flow is improved, but cracks or failures occur in the stent struts
Solution Approach 1:
The patent applies dynamics by incorporating shape memory alloy components that can dynamically change their mechanical properties in response to temperature or stress changes. When the stent is deployed and subjected to body temperature, the shape memory material transforms from a soft phase to a hard phase, providing the necessary strength to withstand cell enlargement procedures without cracking, thus enabling flow path adaptability while maintaining reliability.
Solution Approach 2:
The patent utilizes flexible shell structures where the stent is designed with thin-walled but reinforced geometry. The polymeric layers provide flexibility for delivery and expansion, while embedded metallic reinforcement elements provide the necessary strength to prevent cracking during cell enlargement, allowing the stent to adapt to different flow requirements without compromising structural integrity.
3Ease of operation
If a stent is compressed for intravascular delivery, then the stent can be delivered through catheters, but brittle materials crack or have limited ability to collapse
Solution Approach 1:
The patent utilizes parameter changes by employing shape memory alloys that can reversibly change their mechanical properties through phase transitions. During delivery, the stent is in a martensitic phase (soft and flexible) that allows easy compression and navigation through catheters. Upon deployment at body temperature, it transforms to the austenitic phase (strong and rigid), providing the necessary compressive strength and structural integrity, thus resolving the contradiction between ease of operation and strength.
Solution Approach 2:
The patent employs composite materials combining polymeric stent structures with metallic reinforcement elements. The polymer provides flexibility for compression and delivery, while the metallic components (such as shape memory alloy wires or mesh) provide the necessary strength to withstand compressive forces during delivery and expansion, enabling both ease of operation and maintained strength throughout the delivery process.
Data Source
AI summary
Bioresorbable scaffolds for treatment of bifurcation lesion are described herein. Generally, an expandable scaffold may be fabricated from a high molecular weight isotropic PLLA material, wherein the scaffold incorporates one or more strain relief features which are configured to allow side branch treatment.