Novel Plasma Surface Texturing of Metals for Biomedical Applications

A novel plasma process for creating nano- and micron-scale textures was investigated on several alloys using radio-frequency (RF) inert gas plasmas. Various morphologies with high aspect ratio as well as 3-dimensionally interconnected porous structures have evolved on metal surfaces. The morphologies were found to be varied with alloy composition and/or plasma processes. In this plasma texturing process, metal samples were placed directly on the substrate holder that was electrically connected to an RF electrode. Typical process parameters included power of 200W to 800W, pressures of 20 mTorr to 80 mTorr, and process time of 8 min to 10 min. The resulting microstructures were believed to be formed by the combination of ion sputtering and subsequent materials diffusion due to heating of the metal surfaces. Process variables, including RF energy and pressure, as well as properties of the material to be textured (thermal and electrical transport properties and sample geometry) were all found to affect the degree of texturing and type of microstructure formed. This texturing process provides several advantages over other coating-based texturing processes. A major advantage with this surface modification process is the elimination of concern regarding coating delamination and loose particulates, which would cause serious problems in some biomedical applications. Possible applications of the textured surfaces include drug reservoirs, surfaces that promote tissue or bone in-growth, and other applications benefited by high surface areas.