Biodegradable Stent Closed-Cell Strut Design
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Solution Overview
Problem
Current biodegradable shape memory polymer stents face challenges in achieving an optimal combination of mechanical, biochemical, and technological characteristics, leading to issues such as low radial force and suboptimal configuration, which affects their performance and deployment in vascular applications.
Innovation Solution
A biodegradable shape memory stent with a closed-cell structure is developed, featuring a sinusoidal shape and optimized strut configuration, made from a polymer with specific molecular weight and polydispersity index, allowing for improved mechanical properties and mass production suitability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a biodegradable polymer material is used to create shape memory stents, then the stent can degrade over time and avoid long-term foreign body presence, but the radial force and mechanical strength are reduced compared to metal stents
Solution Approach 1:
The patent employs composite polymer structures combining different biodegradable polymer components with complementary properties. The first polymer provides shape memory effect while the second polymer enhances mechanical strength and radial force, creating a synergistic composite material that resolves the contradiction between biodegradability and mechanical performance
Solution Approach 2:
The patent applies different polymer materials to different regions or layers of the stent structure. By optimizing the local composition and properties of each layer, the stent achieves adequate radial force in critical areas while maintaining overall biodegradability and shape memory functionality
2Strength
If the stent wall is arranged in a webbed configuration, then the stent can provide structural support, but the operational lumen diameter of the vessel is decreased
Solution Approach 1:
The patent divides the stent wall into discrete, optimized strut segments rather than continuous webbed structures. This segmentation allows blood flow to pass more freely through the stent framework while the strategically positioned segments provide necessary structural support, thus increasing the effective operational lumen diameter
Solution Approach 2:
The patent employs curved and sinusoidal strut configurations instead of straight rigid elements. The curved geometry distributes mechanical support more efficiently while creating larger open spaces for blood flow, effectively increasing the operational lumen diameter without compromising structural integrity
3Length of moving object
If the stent is crimped to a small delivery diameter, then the stent can be delivered through catheters, but the ratio of inner diameters before and after crimping affects deployment performance
Solution Approach 1:
The patent utilizes the dynamic shape memory properties of the polymer material to enable the stent to transition between crimped and expanded states. The material's viscoelastic behavior and glass transition characteristics allow reversible deformation, enabling reliable deployment from a small delivery diameter to the final expanded configuration without permanent damage
Solution Approach 2:
The patent controls the crimping and deployment process by manipulating temperature and mechanical stress parameters. By heating the stent above its glass transition temperature during crimping and then allowing it to cool and self-expand, the patent optimizes the diameter ratio and ensures reliable deployment performance while minimizing structural damage
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 stent achieves a favorable ratio of inner diameters before and after crimping, enhanced radial force, and predictable degradation, ensuring effective vascular support and reduced risk of detachment or migration, while maintaining mechanical properties for an extended period.
Implementation Method 1
biodegradable endovascular shape memory polymer stents
Implementation Method 2
The polymer may be obtained by copolymerization of monomers selected from the following group: L-lactide, D-lactide, D,L-lactide, meso-lactide, glycolide, ε-caprolactone, trimethylene carbonate, p-dioxanone
Data Source
AI summary
Biodegradable self-expanding polymer stent has an outer diameter of 0.25-40 mm, length of 5-250 mm, and closed-cell wall structure formed by struts, where ratio of inner diameter values before crimping and after crimping is in a range of 3 to 5, and made of a copolymer obtained from L-lactide, D-lactide, D,L-lactide, meso-lactide, glycolide, ε-caprolactone, trimethylene carbonate, p-dioxanone and compounds comprising functional groups capable of photopolymerization; supramolecular structure of the copolymer is oriented substantially circularly in a transversal cross section of the stent. Method of manufacturing includes extruding a tube of a polymer material; annealing the extruded polymer tube; laser cutting the extruded polymer tube to form a stent workpiece; heating the stent to above glass transition temperature of the polymer, crimping the stent workpiece uniformly over the entire outer surface thereof, and quenching at about minus 20 degrees Celsius; placing the quenched stent on a delivery means.