Iron-Based Bioabsorbable Stent with Nitrided Surface Layer
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Solution Overview
Problem
Current bioabsorbable vascular stents face challenges in achieving a balance between corrosion rate, radial strength, flexibility, and wall thickness, with existing methods failing to optimize comprehensive properties such as radial strength, flexibility, fatigue resistance, and corrosion rate, particularly for thin-walled stents.
Innovation Solution
A bioabsorbable vascular stent with a multi-layer structure is developed, comprising a diffusion layer and a solid solution layer, where the diffusion layer is continuously distributed and free of corrosion-resistant compounds, with a nitrogen content of less than 1 wt-%, and a solid solution layer surrounded by the diffusion layer, optimized through ion nitriding and electrochemical polishing to enhance radial strength and corrosion rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bioabsorbable stent is made from pure iron or iron alloy with thin wall thickness, then flexibility and biodegradability are improved, but radial strength and structural support capability deteriorate
Solution Approach 1:
The patent applies local quality by creating a nitrided surface layer on the iron alloy stent, where only the surface region undergoes nitrogen diffusion to form a hardened layer with enhanced mechanical properties. The core material remains soft and flexible, while the surface provides strength, thus resolving the contradiction between flexibility and radial strength.
2Adaptability or versatility
If a bioabsorbable stent is made from pure iron or iron alloy with thin wall thickness, then flexibility and biodegradability are improved, but fatigue resistance deteriorates
Solution Approach 1:
The nitrided surface layer locally enhances fatigue resistance by creating a hardened, crack-resistant surface zone. This surface treatment provides improved fatigue performance without compromising the overall flexibility of the thin-walled stent structure.
3Productivity
If a bioabsorbable stent is made from magnesium alloy to achieve fast corrosion rate, then biodegradability is improved, but radial strength and structural support capability deteriorate
Solution Approach 1:
The patent changes the material parameter from magnesium alloy to iron or iron alloy, fundamentally altering the corrosion rate and mechanical property profile. This material substitution resolves the contradiction by providing a balance between adequate radial strength and controlled biodegradability that magnesium alloy cannot achieve.
4Strength
If a bioabsorbable stent is made from cobalt-chromium alloy to achieve high radial strength, then structural support capability is improved, but biodegradability and flexibility deteriorate
Solution Approach 1:
The patent changes the material parameter from cobalt-chromium alloy to iron or iron alloy, fundamentally altering both the biodegradability and mechanical property profile. This material substitution resolves the contradiction by providing adequate radial strength while enabling biodegradability that cobalt-chromium alloy cannot achieve.
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 stent achieves a significant increase in radial strength by 31.5% to 94.4% compared to pure iron stents, improved flexibility, and a two-fold increase in corrosion rate, while maintaining a thin wall thickness comparable to cobalt-chromium alloy stents, thereby addressing the limitations of previous bioabsorbable stents.
Implementation Method 1
subjecting a prefabricated component made from an iron-based raw material to ion nitriding treatment
Implementation Method 2
The material composition inside the absorbable component changes with the depth from the surface
Implementation Method 3
electrochemical polishing treatment and/or a chemical polishing treatment to completely remove the corrosion resistant layer
Data Source
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AI summary
A bioabsorbable medical device or a medical device component comprises an absorbable component prepared by subjecting a prefabricated component of an iron-based raw material to ion nitriding. Substance composition inside the absorbable component changes with the depth from the surface. The absorbable component comprises at least a first part and a second part. The first part surrounds the second part. Hardness of the first part is higher than hardness of the second part. An interface exists between the first part and the second part. A crack generated in the first part is impeded by the interface when extending to the second part. On the premise of ensuring radial stand strength, the bioabsorbable medical device or medical device component and a preparation method thereof reduce wall thickness of an iron-based stand, improve a stand corrosion rate and malleability, and achieve broader adaptability.