Thin Strut Bioabsorbable Stent via Multi-Stage Radial Deformation
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Solution Overview
Problem
Current biodegradable stents made from polymers 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.
Innovation Solution
A method involving the use of PLLA polymer with specific molecular weight and crystallinity ranges, combined with multi-stage radial expansion and axial deformation, followed by heat treatment and laser cutting, to create a stent with strut thickness of 130 μm or less, achieving high fatigue and radial strength while maintaining flexibility and biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If biodegradable polymer stents are made with thin struts to minimize arterial injury, then arterial injury is reduced and vascular healing is improved, but radial strength and fatigue resistance become inadequate
Solution Approach 1:
The patent applies parameter changes by controlling the crystallinity of PLLA polymer within a specific range of 40-70% and maintaining molecular weight between 50,000-200,000. These parameter optimizations enable the polymer to achieve both thin strut geometry (≤130 μm) for minimal arterial injury and adequate radial strength through enhanced material properties
Solution Approach 2:
The patent uses PLLA (poly-L-lactide) as a biodegradable polymer material that combines the advantages of biocompatibility and biodegradability with improved mechanical strength. The specific selection of PLLA with controlled crystallinity and molecular weight creates a composite-like structure that achieves both thin strut dimensions and sufficient radial strength to support the vessel
2Object-affected harmful factors
If biodegradable polymer stents are made with thin struts to minimize arterial injury, then vascular healing is promoted, but fatigue resistance becomes insufficient
Solution Approach 1:
The patent optimizes the crystallinity parameter of PLLA to 40-70%, which significantly enhances the fatigue resistance of the polymer. This parameter control allows the stent to maintain both thin strut thickness for minimal arterial injury and high fatigue resistance to withstand cyclic mechanical loads during vessel movement and heartbeat
3Length of moving object
If multi-stage radial expansion is applied to achieve thin strut thickness, then strut thickness is reduced to 130 μm or less, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-heating the PLLA polymer tube to its glass transition temperature range (60-80°C) before radial expansion. This pre-heating softens the polymer, making it more pliable and easier to expand radially through the mold in multiple stages, thereby reducing the overall manufacturing complexity despite the multi-stage process itself
Solution Approach 2:
The patent segments the radial expansion process into multiple stages with progressively increasing pressures. The first stage uses 5-20 psi to achieve initial expansion, the second stage uses 20-50 psi for further expansion, and the third stage uses 50-100 psi for final expansion. This segmentation allows controlled deformation of the polymer at each stage, achieving thin strut thickness while managing manufacturing complexity through systematic pressure control
4Length of moving object
If axial deformation and radial expansion are combined to achieve thin struts, then strut thickness is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary axial deformation to the PLLA tube before radial expansion. By pre-stretching the tube axially to 1.05-1.5 times its original length while heated to glass transition temperature, the polymer structure is prepared and oriented, which facilitates subsequent radial expansion and achieves uniform thin strut thickness with controlled precision
Solution Approach 2:
The patent controls the degree of axial deformation within a specific range (1.05-1.5 times original length) and maintains temperature within the glass transition range (60-80°C) during both axial and radial deformation. These parameter controls ensure that the polymer deforms uniformly and predictably, achieving the desired thin strut thickness while maintaining manufacturing precision
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 resulting stent demonstrates enhanced radial strength, fatigue resistance, and reduced recoil, allowing for effective vascular support and eventual biodegradation, thereby minimizing arterial injury and promoting healing.
Implementation Method 1
heating the tube to a glass transition temperature of from 60° C. to 80° C.
Implementation Method 2
radially expanding the tube by pressurizing the tube with inert gas in multiple stages
Implementation Method 3
The radially deformed tube is then heated at a temperature for few minutes
Data Source
AI summary
This invention discloses a process for preparation of a balloon expandable biodegradable polymer stent with thin struts (strut thickness 130 μm or less, preferably 100-110 μm) with high fatigue and radial strength. The invention discloses a process for the preparation of a biodegradable polymer stent which involves radially deforming the biodegradable polymer tube by applying pressure to it with an inert gas at a predefined temperature in multiple stages with each successive stage having a pressure higher than the pressure applied in a previous stage. The process further involves maintaining the predefined temperature and pressure conditions of each stage for a specified time period after application of the pressure.