Solid-State Drawing Biodegradable Filament Strength
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Solution Overview
Problem
Biodegradable polymers, such as polylactic acid, face limitations in biomedical applications due to insufficient mechanical strength, which restricts their use in demanding applications like surgical sutures and vascular stents, where non-degradable materials with higher strength are typically used.
Innovation Solution
A method involving solid-state drawing and annealing of biodegradable filaments, specifically poly(L-lactic acid) and polyamide, to enhance mechanical strength and flexibility, utilizing a process that includes rotary motors, heat treatment, and shaping to create stents with improved tensile and compressive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biodegradable polymers are used for surgical sutures and vascular stents, then biocompatibility and biodegradability are improved, but mechanical strength deteriorates
Solution Approach 1:
The patent applies parameter changes by subjecting the biodegradable polymer filament to solid-state drawing at controlled temperatures (60-150°C) and draw ratios (1.1-2.0), which modifies the physical structure and crystallinity of the polymer without changing its chemical composition, thereby enhancing mechanical strength while preserving biodegradability
Solution Approach 2:
The patent utilizes phase transitions during the solid-state drawing process, where the polymer undergoes structural reorganization and crystallization at temperatures below its melting point, transforming from an amorphous state to a more ordered crystalline structure that exhibits enhanced mechanical properties
2Strength
If melt extrusion or melt drawing is used to improve mechanical strength, then mechanical strength is improved, but molecular weight and physical properties are lost due to high temperature
Solution Approach 1:
The patent changes the processing temperature parameter from high temperature (melt state) to low temperature (solid state, 60-150°C), fundamentally altering the processing condition to avoid thermal degradation while still achieving the desired mechanical strength improvement through structural reorganization
Solution Approach 2:
The patent replaces the thermal-mechanical melt drawing process with a solid-state drawing process, substituting high-temperature thermal energy with controlled mechanical drawing force applied at low temperatures, thereby achieving strengthening without thermal degradation
3Strength
If injection molding is used to improve mechanical strength, then mechanical strength is improved, but the process becomes very complicated multi-step
Solution Approach 1:
The patent extracts and eliminates unnecessary intermediate steps from complex multi-step processes like injection molding, focusing solely on the essential solid-state drawing operation that directly achieves strength enhancement through a single, simplified process step
Solution Approach 2:
The patent segments the complex manufacturing process into a simple, isolated solid-state drawing step that can be performed independently, separating the essential strengthening function from the complexity of multi-step injection molding processes
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 method significantly increases the mechanical strength and flexibility of biodegradable stents, enabling their use in biomedical applications by maintaining tensile and compressive properties without degrading molecular weight or physical properties, as demonstrated through enhanced tensile strength, modulus of elasticity, and surface smoothness.
Implementation Method 1
a heat treatment oven which is provided between the two rotary motors and heat-treats the filament which is fixed by the jigs and moved by the two rotary motors
Implementation Method 2
a step of shaping and then annealing the drawn biodegradable filament
Data Source
AI summary
A solid-state drawing method for preparing a surgical suture or a biodegradable stent having improved flexibility and mechanical strength. The method for preparing a biodegradable stent includes (a) providing a biodegradable filament that comprises a material which is biodegradable; (b) solid-state drawing the biodegradable filament to provide a drawn biodegradable filament; (c) shaping the drawn biodegradable filament to provide a shaped biodegradable filament; and (d) annealing the shaped biodegradable filament to provide the biodegradable stent, wherein the biodegradable filament has a draw ratio that ranges from 1.1 to 5.0; and wherein the draw ratio is calculated by Equation 1 below:Draw ratio=(LSSD/LO)2,where LO is length of the biodegradable filament before the solid-state drawing, and LSSD is the length of the biodegradable filament after the solid-state drawing.