Surface Modification of Polymethyl Methacrylate by Capacitive-Coupled Plasmas

Surfaces of polymethyl methacrylate (PMMA) plate, an artificial biomedical material, were modified with low pressure RF capacitive-coupled plasma.The influence of the plasma power and gas-type on the surface properties, including the wettability, functional groups and protein absorption resistance, was investigated with atomic force microscopy, X-ray photoelectron spectroscopy and water contact angle measurement.The results show that the plasma power and gas-type had a major impact.For instance, while etching the surface, N₂, air and O₂ plasma produced quite a few grafting functional groups.An increase of the power in lower range significantly improved the wettability and protein adsorption resistance of PMMA surfaces.As the power increased, the adsorption capacity of bovine serum protein decreased, and the two variables followed a descending order:Ar>N₂>Air>O₂.Possible mechanisms were also tentatively discussed.