Shellac Coating for Magnesium Medical Devices
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Solution Overview
Problem
Existing medical devices made from magnesium or magnesium alloys face challenges with uncontrolled corrosion or biodegradation in vivo, leading to rapid hydrogen release and potential adverse effects on tissue healing.
Innovation Solution
A medical device with a shellac coating applied to the device body, which retards degradation by acting as a barrier with limited water permeability, allowing controlled degradation and hydrogen release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnesium is coated with degradable polymer such as polycaprolactone or polylactide, then corrosion or biodegradation is retarded, but degradation is slow and complex manufacture is required
Solution Approach 1:
The patent changes the chemical composition parameter of the coating material from conventional degradable polymers (polycaprolactone, polylactide) to shellac, which has different degradation characteristics. Shellac degrades faster through enzymatic hydrolysis by esterases while maintaining controlled corrosion retardation, thus resolving the contradiction between reliability and productivity.
2Productivity
If fast degradable polymer is used, then degradation speed increases, but polymer swells and volume increases
Solution Approach 1:
The patent changes the material parameter from swelling polymers to shellac, which degrades without significant swelling. Shellac's degradation mechanism through enzymatic hydrolysis does not cause the volume expansion problem associated with fast-degrading polymers, thus resolving the contradiction between productivity and volume control.
3Reliability
If thick degradable polymer coating is applied, then corrosion protection is improved, but device dimensions require complex adjustment
Solution Approach 1:
The patent changes the coating material parameter to shellac, which provides effective corrosion protection at thinner layers compared to conventional polymers. This reduces the need for complex dimensional adjustments and fitting modifications, thus resolving the contradiction between reliability and device complexity.
4Reliability
If magnesium compounds layer is applied, then corrosion resistance is improved, but layers are brittle and tear during manufacture
Solution Approach 1:
The patent changes the coating material from brittle magnesium compounds to shellac, which exhibits ductile behavior and maintains layer integrity during deformation steps. Shellac's organic polymer structure provides flexibility and toughness, preventing tearing and spallation during manufacture, thus resolving the contradiction between reliability and strength.
5Reliability
If degradable polymer coating is used on large medical devices, then beginning corrosion is retarded, but hydrogen release becomes uncontrollable
Solution Approach 1:
The patent changes the degradation mechanism parameter from uncontrolled hydrolysis to enzymatic degradation by esterases. This enzymatic pathway provides more controlled and predictable degradation rates, preventing explosive hydrogen release while maintaining corrosion protection, thus resolving the contradiction between reliability and harmful factor control.
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 shellac coating effectively retards the degradation of magnesium-based medical devices, maintaining desired mechanical properties, reducing hydrogen release, and preventing adverse tissue reactions.
Implementation Method 1
The shellac coating can be in the form of a single-layered or a multi-layered, in particular double-layered, three-layered or four-layered, shellac coating. The device body is at least partially, in particular only partially or completely, covered or coated with the shellac coating.
Data Source
Figure 1~3b
Figure 4~5
Figure 6a~6c
AI summary
The invention relates to a medical device (10) comprising: - a device body (12) preferably comprising a material susceptible to corrosion or biodegradation and - a shellac coating (14), wherein the device body (12) is at least partially covered by the shellac coating (14), wherein the shellac coating (14) has a thickness from 0.1 µm to 20 µm. Further, the invention relates to a method for manufacturing the medical device.