A new method to coat implants with diamond-like carbon (DLC) material was described at an Institute of Physics conference in Chester, UK, by Prof. Joe Franks from Brunel University. The new coating is thought to have anti-infection properties:
At the conference Novel Applications of Surface Modification, organized by the Applied Physics and Technology Division of the Institute of Physics, Professor Joe Franks revealed how medical implants and engineering components can be coated with a diamond-like carbon (DLC) material to make them harder wearing, reduce friction between components, and provide lightweight corrosion protection. Importantly, DLCs, unlike diamond and other coating materials, can be deposited on a surface without having to heat the component to several hundred degrees. This means plastics, as well as metals and ceramics can be coated with DLCs.
The Brunel team have developed new DLC coatings for mechanical and biomedical applications. Mechanical applications include new coatings for drill bits and abrasive materials, non-clogging tungsten carbide milling inserts for engineering applications, and more efficient, lower friction, automotive components that are more fuel efficient.
DLC coatings are also biocompatible and unlike other types of coating don’t trigger the coagulation of blood. Franks reported that they have already provided surgeons at the Royal National Orthopaedic Hospital (RNOH) with DLC-coated knee implants for patients allergic to the metal used.
Professor Joe Franks said: “We’ve also developed coatings that can be used for catheters and various medical implants that go through the skin. The coating is important because it prevents colonization of the tissue by bacteria, such as the superbug MRSA.”
DLC was first produced in 1971 in a vacuum chamber using a technical and costly method that involved spraying charged carbon atoms at the surface to be coated. Subsequent techniques have improved on this. However, Franks and his colleagues have developed a more effective still method known as ‘plasma-assisted chemical vapour deposition’ (PACVD). The component to be coated is mounted in a vacuum chamber on an electrode connected to a high-energy radio wave transmitter. A hydrocarbon gas, such as methane or natural gas, is pumped into the chamber and the radio waves tear apart the hydrocarbon molecules and strip off the electrons from its carbon atoms to produce positive carbon ions. These are attracted to the negatively charged component to produce the coating.
Franks said: “The advantage of this method is that the ionized plasma surrounds the component, which means it does not need not to be manipulated inside the chamber to get an even and uniform coating. The ion energy can be varied as can the composition of the gases in the chamber to vary the properties of the coating, explained Franks.
Franks and his colleagues are working on ways to optimize the coating for specific applications.
The Institute of Physics press release…
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