Absorbable Iron Alloy Implant with Alkaline Buffer Layer
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Solution Overview
Problem
Existing absorbable iron-based alloy medical devices corrode too slowly in the body, leading to prolonged device presence after the treated area has healed, and accelerated corrosion can result in mechanical property failures and increased risk of thrombosis.
Innovation Solution
An absorbable iron-based alloy medical device is developed with an alkaline protector layer on the surface of the iron-based alloy substrate, in addition to a degradable polymer coating. The alkaline protector neutralizes acidic degradation products and acts as a spacer to delay early corrosion, ensuring mechanical integrity during the initial implantation period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the corrosion speed of the iron-based alloy is accelerated to shorten the corrosion cycle, then the device can be completely corroded and absorbed faster after the diseased portion is cured, but the mechanical property and structural integrality of the device during the early stage of implantation (1-6 months) deteriorate
Solution Approach 1:
The coating system is segmented into multiple functional layers: an inner corrosion-resistant coating layer that maintains mechanical integrity during the early implantation stage, and an outer degradable coating layer that accelerates corrosion after the diseased portion is cured. This segmentation allows different parts of the coating to perform different functions at different time points, resolving the contradiction between early mechanical strength and later corrosion acceleration.
Solution Approach 2:
The corrosion-resistant coating layer is applied preliminarily to protect the iron-based alloy substrate during the early implantation stage (1-6 months). This preliminary protective action ensures the device maintains sufficient mechanical property and structural integrality during the critical period when the diseased portion is healing, before the degradable coating layer is degraded to accelerate subsequent corrosion.
2Productivity
If the amount of degradable polyester coating is increased to accelerate corrosion, then the corrosion speed increases and the corrosion cycle shortens, but the early corrosion speed becomes excessively high causing incomplete endothelialization and increasing thrombosis risk
Solution Approach 1:
The coating is segmented into an inner corrosion-resistant layer and an outer degradable polyester layer. The corrosion-resistant layer controls the early corrosion speed to prevent excessive acidification that would harm endothelialization, while the outer degradable layer provides sufficient polyester content to accelerate corrosion after healing. This segmentation resolves the contradiction between achieving high corrosion speed and maintaining reliable endothelialization.
Solution Approach 2:
Different regions of the coating have different properties: the inner layer has corrosion-resistant properties to protect the substrate early on, while the outer layer has degradable properties to accelerate later corrosion. This local differentiation of coating quality allows the device to achieve both controlled early corrosion and accelerated later corrosion, ensuring reliable endothelialization while shortening the overall corrosion cycle.
3Strength
If the amount of degradable polyester coating is reduced to prevent excessive early corrosion, then the mechanical property is maintained, but the corrosion cycle is prolonged and the device cannot be completely corroded within the desired timeframe
Solution Approach 1:
The dual-layer coating structure segments the corrosion control function: the inner corrosion-resistant layer maintains mechanical property during early implantation, while the outer degradable polyester layer ensures sufficient polyester content to accelerate corrosion after healing. This segmentation allows the device to maintain mechanical integrity without requiring excessive polyester reduction, while still achieving complete corrosion within the desired timeframe through the outer layer's degradation.
Solution Approach 2:
The coating system uses composite materials combining corrosion-resistant material in the inner layer and degradable polyester in the outer layer. This composite structure allows the device to benefit from both materials: the corrosion-resistant material maintains mechanical property during early implantation, while the degradable polyester accelerates corrosion after healing, resolving the contradiction between maintaining strength and shortening corrosion cycle.
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 device maintains sufficient mechanical properties during the early stages of implantation (1-6 months) while ensuring complete corrosion and absorption within a desired timeframe, thus addressing the limitations of both slow and rapid corrosion in existing devices.
Implementation Method 1
the alkaline protector neutralizes acidic degradation products and acts as a spacer to delay early corrosion
Implementation Method 2
Degradation of the degradable polyester coating in the body would lower the pH value of a local microenvironment near a device implantation position
Implementation Method 3
forming a local micro acidic environment where the iron-based alloy is corroded faster to generate iron salt and/or iron oxides and/or iron hydroxides serving as corrosion products
Data Source
AI summary
Disclosed are an absorbable iron-based alloy implanted medical device (1) and preparation method thereof. The device (1) comprises an iron-based alloy base (11), a degradable polymer (13) arranged on the surface of the iron-based alloy base, and an alkaline protector (12) arranged on the surface of the iron-based alloy base. The alkaline protector (12) contains at least one alkaline substance capable of neutralizing the acidic substance produced by the polymer at the early stage after the device is implanted to delay the corrosion of the iron-based alloy base (1) in the early stage of implantation, hence the iron-based alloy base (12) would not substantially corrode or would corrode slowly, clinically satisfying the mechanical properties and requirements of the device (1) in the early stage of implantation; and in the meantime, after the neutralization and consumption of the alkaline protector (12) exposes the base (11), the base (11) can still accelerate the corrosion speed thereof in the acidic environment formed by the polymer (13), so as to clinically satisfy the requirement of the corrosion cycle of the device (1) at the same time.