Pre-anodising Metal Implants for Accurate Surface Area
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Solution Overview
Problem
Existing methods for anodizing metal implants, such as those made of titanium, face uncertainty in determining the microscopic surface area due to variations in initial oxide thickness, which affects the calculation of sufficient silver ion absorption for infection suppression, especially when the metal objects are previously treated with sodium hydroxide solutions.
Innovation Solution
A method involving pre-anodising the metal object at a lower voltage to grow a thin, consistent oxide film, followed by electrical measurements to deduce the microscopic surface area, and then anodising to form an integral surface layer with pits, allowing for accurate incorporation of biocidal materials like silver ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the metal object is conditioned by treatment with sodium hydroxide solution, then the initial oxide thickness is significantly dependent on the temperature of the sodium hydroxide solution, but this leads to uncertainty in the thickness of the oxide layer and uncertainty in the calculated surface area
Solution Approach 1:
The patent applies pre-anodising as a preliminary action before the main anodising process. This pre-anodising step creates a consistent initial oxide layer that serves as a reliable baseline for subsequent surface area calculations, eliminating the uncertainty caused by variable initial oxide thickness from sodium hydroxide treatment.
Solution Approach 2:
The patent changes the measurement parameter from direct geometric measurement to electrical capacitance measurement. By measuring the electrical capacitance of the oxide layer, the system can accurately determine surface area without being affected by the chemical treatment history or temperature variations in sodium hydroxide solution.
2Ease of manufacture
If conventional anodising is performed without pre-anodising, then the process is simpler, but the initial oxide thickness varies leading to inaccurate surface area determination
Solution Approach 1:
Pre-anodising serves as a preliminary conditioning step that creates a uniform oxide foundation before the main anodising process. This preliminary action ensures consistent oxide layer formation and enables accurate surface area measurement through capacitance, without significantly complicating the overall manufacturing process.
Solution Approach 2:
The patent replaces mechanical or direct physical measurement methods with electrical capacitance measurement to determine surface area. This substitution provides more precise and reliable measurements of oxide layer thickness and surface area that are not affected by the variability of chemical treatment conditions.
3Quantity of substance
If the microscopic surface area is calculated based on initial oxide thickness, then the calculation can be performed, but the uncertainty in oxide thickness leads to uncertainty in silver ion absorption sufficiency
Solution Approach 1:
The patent replaces the mechanical/physical measurement approach (direct measurement of oxide thickness) with an electrical measurement approach (capacitance measurement). This electrical method provides accurate surface area determination that directly correlates with silver ion absorption capacity, eliminating the uncertainty chain from oxide thickness measurement.
Solution Approach 2:
The electrical capacitance measurement acts as an intermediary parameter that reliably indicates both the surface area and the silver ion absorption capacity. Instead of directly measuring oxide thickness and calculating surface area, the capacitance measurement provides a direct, accurate indicator of the functional properties needed for infection suppression.
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
This approach ensures consistent and accurate ion-absorbing capacity in the anodised surface, reducing the risk of infection by providing a reliable method for determining the microscopic surface area and enhancing the biocidal properties of metal implants.
Implementation Method 1
contacting the metal object with an anodising electrolyte, and pre-anodising the surface so as to grow a thin oxide film on the surface
Implementation Method 2
pre-anodising the surface so as to grow a thin oxide film on the surface
Implementation Method 3
making electrical measurements on the thin oxide film either during or after the pre-anodising step, and hence deducing the surface area of the metal object
Implementation Method 4
anodising the metal object to form an integral surface layer and to form pits through the integral surface layer
Implementation Method 5
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
AI summary
In a process for anodizing a metal object (12), the metal object (12) is contacted with an anodizing electrolyte (32), and is first pre-anodized so as to grow a thin oxide film on the surface. The microscopic surface area is then deduced from electrical measurements either during pre-anodizing or on the pre-anodized surface. The metal object (12) can then be anodized. This is applicable when treating an implant to provide a surface that has the ability to incorporate biocidal material such as silver ions. The pre-anodizing uses a low voltage, for example no more than 2. V, and may take less than 120 seconds.