Anodized Titanium Implant Surface with Biocidal Silver
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Solution Overview
Problem
Metal implants used in surgical procedures face challenges with infection control due to coating detachment from corrosion by body fluids, leading to wear and tissue damage, and existing methods fail to provide a durable and non-toxic biocidal surface layer.
Innovation Solution
A method involving anodising titanium metal implants at a voltage above 50 V for at least 30 minutes to create a dense hard surface layer with shallow pits, followed by ion exchange to incorporate biocidal metal ions, such as silver, which controls the release rate and quantity to prevent toxicity and maintain a polished finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating (titanium nitride or silver) is applied to the metal implant, then the biocidal effect and wear resistance are improved, but the coating may detach due to corrosion from body fluids, causing tissue damage
Solution Approach 1:
The patent applies high-voltage anodising (above 50 V) to change the electrochemical parameters of the titanium surface, transforming it into a porous oxide layer that can incorporate biocidal metal ions. This parameter change enables the surface to achieve both biocidal functionality and corrosion resistance without requiring traditional coatings that are prone to detachment.
Solution Approach 2:
The patent creates a composite structure by incorporating biocidal metal ions (such as silver, gold, platinum, palladium, copper, tin, antimony, lead, bismuth, or zinc) into the anodised oxide layer on the titanium implant. This composite approach combines the biocidal properties of metal ions with the corrosion resistance of the titanium oxide matrix, eliminating the need for separate coatings.
2Reliability
If biocidal metal ions are incorporated into the surface layer, then the biocidal effect is improved, but the release rate must be controlled to avoid toxic effects on body cells
Solution Approach 1:
The patent controls the release rate of biocidal metal ions by adjusting the anodising voltage (above 50 V) and duration, which determines the porosity, thickness, and surface area of the oxide layer. These parameter changes regulate the diffusion and release kinetics of metal ions, ensuring sufficient biocidal activity while preventing excessive release that could be toxic to body cells.
Solution Approach 2:
The high-voltage anodising process creates a porous oxide layer structure that controls the release of biocidal metal ions through diffusion. The porosity provides pathways for ion release while the matrix structure limits the total quantity released, achieving a balanced biocidal effect without excessive toxicity to surrounding tissues.
3Strength
If the anodising voltage is increased to generate a denser surface layer, then the wear resistance is improved, but the surface finish may be affected
Solution Approach 1:
The patent optimizes the anodising voltage parameter (using high voltage above 50 V, typically 50-150 V) to simultaneously achieve a dense hard surface layer and maintain a polished finish. This specific voltage range creates the necessary oxide layer density for wear resistance while preserving the surface smoothness, avoiding the milky or matt appearance associated with lower voltage anodising.
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 generates a durable, biocidal surface layer that effectively suppresses infection for up to 6 months with controlled silver release, minimizing toxic effects and maintaining the implant's surface finish, thereby reducing wear and tissue damage.
Implementation Method 1
anodising the implant at a voltage above 50 V for a period of at least 30 min, so as to generate a surface layer
Implementation Method 2
anodising the implant at a voltage above 50 V for a period of at least 30 min, so as to generate a surface layer
Implementation Method 3
performing ion exchange so as to incorporate ions of a biocidal metal into the surface layer
Implementation Method 4
The implant is cleaned ultrasonically using first acetone as the liquid phase, and then a 1 M aqueous solution of sodium hydroxide
Data Source
AI summary
A metal implant for use in a surgical procedure is provided with a surface layer that is integral with the metal substrate, and which incorporates a biocidal material. The surface layer is grown by anodizing at a voltage between 50 and 150 V, and the biocidal material incorporated in it by ion exchange. This produces a significantly harder surface than anodizing at low voltage, and generates pits containing ion-absorbing material.