Anodised Metal Surface with Cyclic Voltage Porosity
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Solution Overview
Problem
Existing methods for treating metal objects to impart biocidal properties are inconsistent and time-consuming, especially with more passive metal alloys, and do not effectively promote tissue integration while ensuring a safe and effective biocidal level for medical implants.
Innovation Solution
A surface treatment method involving cyclic voltage application during anodising to form a surface layer with regions of high oxygen to metal atom ratio, incorporating bio-effective materials like silver into these regions, which are more available for elution and biofilm prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anodising methods are used to form a surface layer on metal objects, then a passive oxide layer is formed, but the process requires prolonged time and produces inconsistent results, particularly with more passive alloys
Solution Approach 1:
The patent applies periodic voltage cycling during the anodising process, alternating between forward voltage (to grow the oxide layer) and reverse voltage (to create porous structure). This periodic action enables consistent formation of surface layers with controlled porosity and biocidal material loading, significantly reducing process time while improving reliability across different metal alloys including more passive ones.
2Ease of manufacture
If the metal object surface is polished or smooth, then the surface is easier to manufacture, but the ability to promote tissue integration and osseointegration is reduced
Solution Approach 1:
The patent creates local porous structures through voltage cycling during anodising, where the surface layer contains regions of high porosity (pits) that specifically promote tissue integration. This local quality change allows the bulk surface to remain relatively simple while specific zones provide enhanced bioactivity and osseointegration capability.
Solution Approach 2:
The patent forms a porous oxide surface layer through controlled anodising with voltage cycling. The porous structure increases surface area and provides pathways for tissue ingrowth and osseointegration, significantly enhancing tissue integration capability while maintaining ease of manufacture through a single-step electrochemical process.
3Object-affected harmful factors
If a biocidal material is incorporated into the surface layer, then infection risk is reduced, but achieving consistent and biologically acceptable levels is difficult with conventional methods
Solution Approach 1:
The patent uses feedback control through voltage cycling, where the electrochemical responses during anodising provide real-time information about surface layer formation. This allows precise control over porosity and thickness, ensuring consistent biocidal material loading at biologically acceptable levels. The cyclic voltage profile adjusts based on current measurements, providing feedback control over the incorporation 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 reduces treatment time, achieves consistent biocidal loading, and promotes tissue integration by maintaining surface roughness and distributing bio-effective materials uniformly, enhancing the biocompatibility and infection control of metal objects.
Implementation Method 1
anodising the metal object to form an integral surface layer
Implementation Method 2
forming an anodised oxide layer on the metal object
Implementation Method 3
producing a hydrous metal oxide in said regions in the oxide layer by electrochemical or chemical reduction
Implementation Method 4
producing a hydrous metal oxide in said regions in the oxide layer by electrochemical or chemical reduction
Implementation Method 5
contacting the anodised metal object with a solution containing a bio-effective material so as to incorporate said bio-effective material into the surface layer
Data Source
Figure 1~2
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Figure 4~5
AI summary
Metal objects are treated by anodising the metal object in contact with an aqueous electrolyte, and then subjecting the anodised metal object to a reversed voltage. The anodising is performed in two stages, firstly to passivate with the formation of an oxide layer, and secondly to form regions in the oxide layer having a higher oxygen to metal atom ratio, for example pits or caps, in this oxide layer. The second stage of anodising is performed by applying a multiplicity of voltage cycles, each voltage cycle involving ramping the voltage between a lower threshold voltage and an upper threshold voltage, and then returning to the lower threshold voltage. The reversed voltage step forms a hydrous metal oxide in the regions of higher oxygen to metal atom ratio, and the oxide layer and hydrous metal oxide together constitute a surface layer which is integral with the metal object, and has ion exchange capacity. After the reversed voltage step the metal object is then contacted with a bio-effective material such as a biocidal metal, which is absorbed into the surface of the metal object. The processing time may be reduced by applying the multiple voltage cycles. The invention also provides a treated metal object which can be prepared by treating a metal object having a micro-rough surface according to the method described above.