Anodized Titanium Surface with Embedded Silver for Biocidal Coating
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Solution Overview
Problem
Metal objects, particularly those made of titanium and its alloys, used in medical implants and jewelry can cause irritation and infection due to corrosion and biofilm formation when in contact with body tissues, as existing biocidal coatings like metallic silver may detach, leading to tissue damage and increased wear.
Innovation Solution
An anodizing method is developed to create a surface layer with integral biocidal properties on metals like titanium, niobium, and zirconium, involving a two-stage process of passivation and voltage reversal to form pits within the substrate, which are then filled with a biocidal material such as silver, enhancing the surface's biocidal and hardwearing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic silver is electroplated onto metal to provide biocidal properties, then infection control is improved, but the coating may detach due to corrosion and passivation, causing tissue damage and increased wear
Solution Approach 1:
The patent applies preliminary action by creating an anodised surface layer with embedded silver particles before the metal is exposed to body fluids. The silver is incorporated into the anodised layer during the anodising process itself, rather than applying a separate electroplated coating that would later detach. This preliminary incorporation ensures the biocidal agent remains stable and integrated with the metal surface throughout its service life.
Solution Approach 2:
The anodised metal oxide layer serves as an intermediary between the metal substrate and the biocidal silver particles. This intermediate layer provides a stable matrix that embeds and secures the silver particles, preventing their detachment while still allowing the silver to exert its biocidal effect. The anodised layer acts as a mediator that combines the structural stability of the metal with the biocidal functionality of silver.
2Ease of manufacture
If metal alloys are used in jewellery to reduce cost, then economic feasibility is improved, but impurities in the alloy react with moisture and chloride ions, causing pitting and bacterial accumulation
Solution Approach 1:
The patent applies local quality by treating only the surface layer of the metal alloy with anodising, rather than requiring the bulk material to be pure. The anodised surface layer with embedded silver provides the biocidal protection locally at the interface with skin and moisture, while the underlying alloy structure can remain cost-effective. This localized treatment eliminates the need for expensive pure metals throughout the entire jewellery piece.
Solution Approach 2:
The patent changes the chemical and physical parameters of the metal surface through anodising. The electrochemical process transforms the surface composition by creating a metal oxide layer with different properties than the bulk alloy. This parameter change at the surface level provides corrosion resistance and biocidal functionality without altering the cost-effective alloy composition of the bulk material.
3Strength
If anodising is used to create a hardwearing surface layer, then wear resistance is improved, but the process complexity increases due to multiple voltage application stages
Solution Approach 1:
The patent merges multiple functions into a single anodising process. The anodising operation simultaneously creates the hardwearing oxide surface layer, embeds the biocidal silver particles, and forms the integral coating structure. By combining these functions into one integrated process rather than separate steps, the patent reduces overall process complexity while achieving multiple desirable outcomes.
Solution Approach 2:
The anodising process serves multiple universal functions: it provides wear resistance through the hardened oxide layer, incorporates biocidal silver particles, and creates a stable integral coating. This multi-functional approach allows a single process to address several requirements (hardness, biocidality, coating stability) that would otherwise require separate treatment steps, thereby simplifying the overall manufacturing process.
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 method results in a metal surface with improved biocidal and bacteriostatic properties, reducing the risk of infection and biofilm formation, while maintaining the material's strength and biocompatibility, with consistent and enhanced silver loading for effective antimicrobial action.
Implementation Method 1
passivating the metal object to form an anodised integral surface layer on the metal object by applying a positive potential
Implementation Method 2
producing a hydrous metal oxide or phosphate by (i) either applying a negative voltage to the metal object that has been anodised during steps (a and b), while in contact with the anodising electrolyte, or (ii) contacting the metal object that has been anodized during steps (a and b) with an electrolyte solution containing a reducible soluble salt of titanium or the substrate metal and applying a negative voltage
Implementation Method 3
contacting the anodised metal object with a solution containing a biocidal material so as to incorporate said biocidal material into the surface layer
Data Source
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AI summary
Metal objects are treated by anodising the metal object in contact with an acidic solution, and then subjecting the anodised metal object to a reversed voltage (compared to the anodising voltage). The thus- treated metal object is then contacted with a biocidal metal-containing solution. Biocidal metal is deposited on the surface of the metal object, resulting in improved biocidal properties.