Intravascular Stent Wire Mixed Oxide Layer
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Solution Overview
Problem
Existing intravascular implants, such as stents and flow diverters, face challenges with biocompatibility and mechanical properties due to rapid wear of oxide layers, particularly in wire mesh structures, which leads to nickel release and impaired compatibility.
Innovation Solution
A method involving surface treatment of wires with a mixed oxide layer of 250 nm to 400 nm thickness, formed through heat treatment in a salt bath, providing a dense diffusion barrier and improved mechanical properties, allowing for the use of mechanical polishing instead of electropolishing, and maintaining anisotropic roughness for enhanced implant performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thin oxide layer is formed on the wire surface, then nickel diffusion into the body is reduced and biocompatibility is improved, but the oxide layer wears out quickly and mechanical properties deteriorate
Solution Approach 1:
The patent changes the thickness parameter of the oxide layer from conventional thin layers (10 nm) to a thicker range (250-400 nm). This parameter change resolves the contradiction by providing sufficient thickness to prevent nickel diffusion while maintaining durability, as the thicker layer withstands wear better than thin layers while still forming an effective diffusion barrier.
Solution Approach 2:
The patent creates a composite surface structure consisting of a mixed oxide layer containing multiple metal oxides (such as TiO2, Nb2O5, Ta2O5) on the wire surface. This composite oxide layer combines the benefits of nickel diffusion prevention with improved mechanical properties and wear resistance, resolving the contradiction between biocompatibility and durability.
2Object-affected harmful factors
If electropolishing is used to create a smooth surface, then biocompatibility is improved, but manufacturing costs increase and anisotropic roughness is lost
Solution Approach 1:
The patent changes the surface roughness parameter by maintaining anisotropic roughness (Rq = 0.02 μm to 0.5 μm) instead of creating a perfectly smooth surface through electropolishing. This parameter change allows the use of mechanical polishing methods which are more cost-effective while still achieving good biocompatibility through the oxide layer formation.
Solution Approach 2:
The patent replaces the electropolishing process (electrochemical mechanical system) with mechanical polishing methods. This substitution reduces manufacturing costs while the subsequent oxide layer formation compensates for the rougher surface, maintaining biocompatibility without the high costs of electropolishing.
3Adaptability or versatility
If wire meshes are used instead of laser-manufactured stents, then deformability and compliance are improved, but oxide layer wear increases leading to nickel release
Solution Approach 1:
The patent applies a composite mixed oxide layer containing multiple metal oxides on the wire mesh surface. This composite layer provides a durable barrier that prevents nickel release from the superelastic NiTi alloy wires, allowing the wire mesh structure to maintain its superior deformability and compliance without the harmful nickel release problem.
Solution Approach 2:
The patent changes the oxide layer thickness parameter to 250-400 nm, which is sufficiently thick to prevent nickel diffusion while being thin enough to maintain the wire mesh's deformability. This parameter change resolves the contradiction by providing protection without sacrificing the mechanical flexibility needed for wire mesh implants.
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 solution significantly reduces nickel diffusion, enhances biocompatibility, improves mechanical properties, and reduces wear, while allowing for cost-effective surface treatment methods, resulting in improved crimping and sliding behavior of the implants.
Implementation Method 1
heat treatment in a special salt bath... heat treatment in a salt bath, providing a dense diffusion barrier... surface treatment of wires with a mixed oxide layer
Data Source
AI summary
The invention relates to an intravascular functional element, in particular an implant, more particularly a stent, flow diverter, stent graft and intravascular occlusion device, having a radially self-expandable lattice structure (12) which is tubular at least in some regions and which has a wire (10) or a plurality of wires (10), wherein the wire (10)/at least one of the wires (10) comprises a superelastic material, in particular a superelastic material of an alloy with the alloy elements nickel and titanium, wherein a mixed oxide layer is formed on the surface of the wire (10)/of the wires (10) with a layer thickness of 150 nm to 400 nm, in particular 200 nm to 350 nm, in particular 250 nm to 300 nm.