Thin Strut Bioabsorbable Stent Fatigue Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current biodegradable stents made from polymers face challenges in achieving adequate radial strength, fatigue resistance, and low recoil with thin strut thickness, which is essential for minimizing arterial injury and ensuring proper vascular healing, while also maintaining mechanical integrity and flexibility for crimping and deployment.
Innovation Solution
A biodegradable stent with struts of 130 μm or less in thickness is manufactured using a process involving extruded PLLA tubes that are axially and radially deformed under controlled temperature and pressure conditions, followed by laser cutting and annealing, and coated with therapeutic agents for enhanced mechanical properties and sterilization using reduced e-beam doses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thin struts (130 μm or less) are used to minimize arterial injury, then arterial injury is reduced and vascular healing is improved, but radial strength and fatigue resistance become insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the glass transition temperature (55-65°C) and crystallinity (35-45%) of the PLLA polymer, along with specific deformation ratios (axial 1.2-1.5, radial 2.0-3.0) during manufacturing. These parameter optimizations enable thin struts (130 μm or less) to achieve both low arterial injury and sufficient radial strength (≥20 N) with adequate fatigue resistance
Solution Approach 2:
The patent uses composite material approach by combining PLLA polymer with specific molecular weight characteristics (Mw 590,000-620,000; Mn 350,000-370,000; PDI 1.6-1.8) and optimizing its crystalline structure. This composite approach at molecular and structural levels allows thin struts to maintain mechanical integrity while minimizing arterial trauma
2Object-affected harmful factors
If thin struts (130 μm or less) are used to minimize arterial injury, then vascular healing is enhanced, but recoil increases due to reduced structural support
Solution Approach 1:
The patent controls the glass transition temperature (55-65°C) and crystallinity (35-45%) parameters of PLLA to optimize the balance between flexibility for crimping and structural stability to minimize recoil. This parameter optimization allows thin struts to maintain low profile during delivery while providing adequate radial support after deployment
Solution Approach 2:
The patent applies dynamics principle by designing the stent with controlled elastic properties through PLLA parameter optimization. The stent exhibits dynamic behavior: highly flexible during crimping and delivery, then provides stable radial support after deployment with recoil minimized through optimized polymer crystallinity and cross-linking density
3Volume of moving object
If thin struts are used to minimize arterial injury, then the stent profile is reduced, but mechanical integrity during crimping and deployment becomes compromised
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: glass transition temperature (55-65°C), crystallinity (35-45%), molecular weight (Mw 590,000-620,000), and polydispersity index (1.6-1.8). These parameter changes enable thin struts to maintain mechanical integrity during crimping and deployment while achieving low profile for minimally invasive delivery
Solution Approach 2:
The patent applies preliminary action by pre-optimizing the PLLA polymer properties and stent scaffold design before manufacturing. The polymer is pre-characterized for molecular weight, PDI, and thermal properties, and the scaffold geometry is pre-designed with appropriate strut thickness and cell size ratios. This preliminary optimization ensures thin struts can withstand crimping and deployment stresses while maintaining low profile
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 process results in a stent with high fatigue and radial strength, low recoil, and adequate strut thickness, reducing arterial injury and enabling effective vascular healing, while maintaining the stent's mechanical integrity and flexibility for crimping and deployment.
Implementation Method 1
radially expanding the tube at a temperature of 70°C. to 80°C. by pressurizing the tube with inert gas
Implementation Method 2
Cutting specific pattern of scaffold structure on the deformed tube by laser machining
Implementation Method 3
Heating the tube after radial deformation under the same pressure conditions between 100°C. and 110°C. and maintaining for up to 2 min
Implementation Method 4
Sterilizing the crimped stent and catheter system by e-beam method with e-beam dose less than 20 kGy
Data Source
AI summary
This invention discloses method of manufacture of balloon expandable stent made from bioabsorbable polymer with thin struts (strut thickness 130 μm or less, preferably 100-110 μm) with high fatigue and radial strength. The invention further discloses balloon expandable stent made from bioabsorbable polymer with thin struts (strut thickness 130 μm or less, preferably 100-110 μm) with high fatigue and radial strength.