Bioabsorbable Stent Axial Radial Deformation Fatigue Strength
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Solution Overview
Problem
Current polymeric stents face challenges in achieving adequate radial strength, fatigue resistance, and low recoil while maintaining thin strut thickness, which is essential for minimizing arterial injury and ensuring proper vascular healing, as they tend to have lower mechanical properties compared to metallic stents, leading to potential recoil and fracture issues during crimping and deployment.
Innovation Solution
A biodegradable stent with thin struts (less than 130 μm thickness) made from bioabsorbable polymers like PLLA, processed through extrusion, axial and radial deformation, and laser cutting to enhance mechanical properties, combined with a reduced e-beam radiation sterilization dose to maintain polymer integrity, ensuring high fatigue and radial strength while minimizing recoil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thin strut thickness is used to minimize arterial injury, then vascular healing is improved, but radial strength and fatigue resistance deteriorate
Solution Approach 1:
The patent employs composite material structures by combining bioabsorbable polymers with specific structural configurations (interlocking struts, optimized patterns) to achieve high radial strength and fatigue resistance while maintaining thin strut thickness. The composite approach integrates multiple material properties and structural elements to resolve the contradiction between thin struts for minimal arterial injury and sufficient mechanical strength for vascular support.
Solution Approach 2:
The patent utilizes parameter changes in the polymer material properties, including controlling crystallinity, molecular weight, and degradation rate, to optimize the balance between mechanical strength and thin strut design. By adjusting these parameters, the stent achieves adequate radial strength and fatigue resistance while maintaining minimal strut thickness for reduced arterial injury.
2Object-affected harmful factors
If thin strut thickness is used to minimize arterial injury, then vascular healing is improved, but fatigue resistance deteriorates
Solution Approach 1:
The patent employs composite material structures by combining bioabsorbable polymers with specific structural configurations (interlocking struts, optimized patterns) to achieve high radial strength and fatigue resistance while maintaining thin strut thickness. The composite approach integrates multiple material properties and structural elements to resolve the contradiction between thin struts for minimal arterial injury and sufficient mechanical strength for vascular support.
Solution Approach 2:
The patent utilizes parameter changes in the polymer material properties, including controlling crystallinity, molecular weight, and degradation rate, to optimize the balance between mechanical strength and thin strut design. By adjusting these parameters, the stent achieves adequate radial strength and fatigue resistance while maintaining minimal strut thickness for reduced arterial injury.
3Reliability
If high e-beam radiation dose is used for sterilization, then sterilization effectiveness is improved, but polymer integrity deteriorates
Solution Approach 1:
The patent optimizes the e-beam radiation sterilization parameters by adjusting dose, dose rate, and environmental conditions to achieve effective sterilization while minimizing polymer degradation. This parameter optimization resolves the contradiction between sterilization effectiveness and polymer integrity preservation.
Solution Approach 2:
The patent introduces intermediary substances or environmental modifications during e-beam sterilization to protect the polymer from excessive radiation damage while maintaining sterilization effectiveness. This intermediary approach allows achieving both sterilization reliability and polymer composition stability.
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 solution provides a stent with improved radial strength, fatigue resistance, and reduced recoil, allowing for effective vascular support until healing is complete and eventual biodegradation, while minimizing arterial injury and maintaining polymer integrity.
Implementation Method 1
processed through extrusion, axial and radial deformation
Implementation Method 2
The stent material attains plastic deformation and hence the stent does not recoil back to its original shape
Implementation Method 3
cutting specific pattern of scaffold structure on the expanded tube by laser machining
Implementation Method 4
reduced e-beam radiation sterilization dose to maintain polymer integrity
Data Source
AI summary
The invention discloses a process for the preparation of a biodegradable stent which involves deforming an extruded biodegradable polymer tube axially at a first predefined temperature by applying an axial force for a first predefined time interval. The process is followed by radially expanding the axially stretched tube at a second predefined temperature by pressurizing the tube with an inert gas in one or more stages, the pressure applied in each successive stage being higher than the pressure applied in a previous stage. The process further comprises laser cutting a specific pattern of scaffold structure on the expanded tube and then crimping the laser cut stent on the balloon of delivery catheter in a sterile environment in multiple stages.