Bioabsorbable Stent Crystalline Morphology Control
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Solution Overview
Problem
Conventional stents made from semi-crystalline polymers like PLLA lack adequate radial strength and fracture toughness, leading to mechanical failure and recoil issues due to their brittle nature, which is exacerbated by insufficient processing to enhance these properties.
Innovation Solution
A method involving radially expanding and axially elongating PLLA tubes by increasing pressure and applying a tensile force, while heating and cooling within specific temperature ranges, to modify the crystalline morphology and enhance the mechanical properties of the stent, achieving a % radial expansion of 300-500% and 20-200% axial elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional semi-crystalline polymer stents are used, then the stent can be manufactured with basic structural integrity, but the radial strength and fracture toughness are insufficient leading to mechanical failure
Solution Approach 1:
The patent applies parameter changes by controlling the crystallization process through specific temperature ranges (below melting point but above room temperature) and deformation conditions during manufacturing. This transforms the crystalline morphology from conventional insufficient structures to optimized configurations with enhanced radial strength and fracture toughness, directly resolving the mechanical failure resistance issue while maintaining manufacturability.
Solution Approach 2:
The patent creates a composite-like structure within the semi-crystalline polymer by developing a specific crystalline morphology that combines rigid crystalline regions for strength with controlled amorphous regions for toughness. This internal composite architecture provides both the required radial strength and resistance to mechanical failure that conventional homogeneous structures cannot achieve.
2Strength
If conventional semi-crystalline polymer stents are used, then the stent can be manufactured with basic structural integrity, but the fracture toughness is insufficient leading to brittle nature
Solution Approach 1:
The patent changes the physical parameters of the polymer during manufacturing, specifically controlling crystallization temperature and deformation conditions. These parameter changes produce a crystalline morphology that enhances fracture toughness by creating a structure that can absorb and distribute stress, reducing the brittle nature while maintaining the semi-crystalline polymer's inherent advantages.
3Strength
If conventional processing methods are used, then the stent manufacturing is simple, but the radial strength and dimensional stability are inadequate
Solution Approach 1:
The patent applies preliminary action by incorporating crystallization control and deformation processing during the initial manufacturing stage rather than as a separate post-processing step. This preliminary action achieves the desired crystalline morphology and enhanced radial strength within the existing manufacturing workflow, minimizing additional complexity while significantly improving performance.
4Duration of action of stationary object
If conventional stent structures are used, then the stent can be deployed, but recoil and crack formation occur reducing longevity
Solution Approach 1:
The patent changes the material parameters through controlled crystallization to create a more stable structural configuration. This parameter change reduces recoil by enhancing the stent's memory and structural integrity, while also preventing crack formation by eliminating weak points in the crystalline structure, thereby extending stent longevity.
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 significantly improves the radial strength, fracture toughness, and dimensional stability of the stent, reducing recoil and crack formation, thereby enhancing the overall performance and longevity of the stent within the body.
Implementation Method 1
heating and cooling within specific temperature ranges
Implementation Method 2
heating and cooling within specific temperature ranges
Implementation Method 3
radially expanding and axially elongating PLLA tubes by increasing pressure
Implementation Method 4
applying a tensile force, while heating and cooling within specific temperature ranges
Implementation Method 5
modify the crystalline morphology
Data Source
AI summary
Methods to expand polymer tubing with desirable or optimum morphology and mechanical properties for stem manufacture and fabrication of a stent therefrom are disclosed.