Swellable Coating on X-ray Markers for Absorbable Scaffolds
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Solution Overview
Problem
Medical implants with X-ray markers face challenges in corrosion due to interaction with the framework, especially in aqueous environments, leading to reduced X-ray visibility and increased corrosion rates, which can result in undesirable biological reactions.
Innovation Solution
A medical implant with a swellable, electrically insulating coating on monolithic X-ray markers that increases in volume upon contact with water, preventing contact with the framework and ensuring self-centering and self-passivation, thereby reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a solid X-ray marker is bonded into the eyelet of an absorbable scaffold, then the marker position can be determined, but corrosion-promoting contact between the marker and scaffold occurs due to adhesive gap displacement
Solution Approach 1:
A polymer coating is applied as an intermediary layer between the X-ray marker and the absorbable scaffold. This coating prevents direct metallic contact between the marker and scaffold, eliminating galvanic corrosion while maintaining the marker's X-ray visibility and positional stability throughout the scaffold's degradation process.
Solution Approach 2:
The polymer coating's physical state changes from a liquid or paste application state to a solid protective layer after curing. This parameter change enables the coating to fill irregularities in the eyelet-marker interface and maintain stable separation as the scaffold degrades, preventing adhesive gap displacement and marker migration.
2Measurement precision
If composite radiopaque markers with high radiopaque particle content are used, then X-ray visibility is improved, but the mixture becomes too viscous for processing
Solution Approach 1:
The radiopaque function is extracted from the adhesive composite and concentrated into a separate, pre-formed solid X-ray marker. This allows the marker to achieve high radiopaque particle content (up to 100% by weight) for optimal X-ray visibility without the viscosity constraints that would prevent processing if such high concentrations were used in an injectable adhesive.
3Reliability
If the adhesive gap is uniformly distributed around the marker circumference, then marker displacement is prevented, but technological limitations prevent uniform distribution
Solution Approach 1:
The polymer coating transforms from an application state (liquid or paste) to a final solid state, during which it shrinks and conforms to the marker surface. This parameter change enables the coating to uniformly fill the eyelet space around the marker circumference, creating consistent spacing and preventing marker displacement without requiring precise control of adhesive gap uniformity during assembly.
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 swellable coating effectively prevents corrosion by spacing the X-ray markers from the framework, maintaining X-ray visibility and ensuring the degradation process is not interrupted, while simplifying the manufacturing process and reducing the risk of local element formation.
Implementation Method 1
the coating is designed to be swellable such that it experiences an increase in volume upon contact with a water-containing medium
Data Source
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AI summary
The invention relates to a medical implant comprising: a framework (1) having at least one receptacle (2) for an X-ray marker (5), wherein the framework (1) comprises a first metal, and at least one X-ray marker (5) arranged in the receptacle (10), wherein the X-ray marker (5) comprises a second metal. According to the invention, the X-ray marker (5) comprises a second metal, and an electrically insulating coating (3) is applied to the X-ray marker (5) to prevent corrosion-promoting contact between the X-ray marker (5) and the framework (1).