Fe-Mn-X Biodegradable Alloy Wire for Stents
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Solution Overview
Problem
Current biodegradable stents face challenges with mechanical strength and controlled degradation rates, often experiencing pitting corrosion and inadequate elasticity, which can lead to premature failure and complications in biomedical applications.
Innovation Solution
A biodegradable wire material composed of iron (Fe) and manganese (Mn) with added nitrogen (N) and optionally molybdenum (Mo) or chromium (Cr) is developed to control corrosion and prevent pitting, ensuring controlled degradation and enhanced mechanical properties, suitable for use in stents and other medical devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If iron-manganese alloys are used to achieve faster biodegradation, then the degradation rate is improved, but the elasticity and yield strength become insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the alloy by adding specific elements (nitrogen, molybdenum, chromium) to the iron-manganese base alloy. This modifies the material properties to achieve both adequate strength and controlled biodegradation rate, resolving the contradiction between degradation speed and mechanical strength.
Solution Approach 2:
The invention creates a composite alloy system Fe-Mn-X where X represents additional alloying elements (nitrogen, molybdenum, chromium). This composite material approach combines the biodegradation benefits of iron-manganese alloys with the strength and corrosion resistance properties of the additional elements, simultaneously addressing both the degradation rate and mechanical strength requirements.
2Strength
If cold worked Fe-Mn alloys are used to enhance strength, then the strength is improved, but stress corrosion cracking and pitting corrosion occur
Solution Approach 1:
The invention converts the harmful effect of cold working (which causes stress corrosion cracking) into a beneficial outcome by adding alloying elements that specifically protect against these corrosion mechanisms. The nitrogen, molybdenum, and chromium elements form protective phases and improve corrosion resistance, allowing the cold-worked structure to be maintained while eliminating the corrosion vulnerability.
Solution Approach 2:
The additional alloying elements (nitrogen, molybdenum, chromium) act as intermediaries that mediate between the cold-worked microstructure and the corrosive environment. These elements form protective oxide films and modify the corrosion behavior, preventing direct attack on the cold-worked iron-manganese alloy structure.
3Duration of action of moving object
If pure iron wire is used to achieve slow degradation, then the degradation rate is controlled, but the degradation time is excessive (about 2 years)
Solution Approach 1:
The invention adjusts the degradation time parameter by modifying the alloy composition from pure iron to iron-manganese with additional elements. This compositional change accelerates the degradation rate from 2 years (pure iron) to an optimal range for medical applications, while maintaining controlled and uniform degradation through the specific alloying strategy.
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 Fe-Mn-X wire material maintains mechanical strength and resilience, preventing pitting corrosion and ensuring controlled biodegradation, thus reducing the risk of material fracture and promoting endothelial vasoreactivity and long-term hemodynamic stability.
Implementation Method 1
control corrosion in an in vivo environment
Implementation Method 2
ensuring controlled biodegradation
Implementation Method 3
maintains mechanical strength and resilience
Implementation Method 4
enhanced mechanical properties
Implementation Method 5
a desirable dissolution rate may be achieved by the alloying of manganese with iron
Data Source
Figure 1A~2
Figure 3a~3b
Figure 3c~3d
AI summary
A bioabsorbable wire material includes manganese (Mn) and iron (Fe). One or more additional constituent materials (X) are added to control corrosion in an in vivo environment and, in particular, to prevent and/or substantially reduce the potential for pitting corrosion. For example, the (X) element in the Fe-Mn-X system may include nitrogen (N), molybdenum (Mo) or chromium (Cr), or a combination of these. This promotes controlled degradation of the wire material, such that a high percentage loss of material the overall material mass and volume may occur without fracture of the wire material into multiple wire fragments. In some embodiments, the wire material may have retained cold work for enhanced strength, such as for medical applications. In some applications, the wire material may be a fine wire suitable for use in resorbable in vivo structures such as stents.