Anti-bacterial property of hydrogen-free amorphous carbon coatings on Ar plasma-pretreated polytetrafluoroethylene (PTFE) with a-C:H:Finterlayer

Amorphous carbon (a-C) films have a growing interest in the biological and medical field, as a coating material, due to their biocompatibility and antibacterial property. However, a-C films deposited directly on polymers often show adhesion failure. In this paper, two types of a-C films, amorphous hydrogenated carbon (a-C:H) film and hydrogen-free a-C (H-free a-C) film were deposited on polytetrafluoroethylene (PTFE) using a plasma deposition method. Prior to a-C film coating, the PTFE substrates were treated with Ar and O ₂ plasma and an appropriate interlayer was chosen to enhance the adhesion strength. The effect of the plasma pretreatment on the chemical composition of the PTFE was investigated by X-ray photoelectron spectroscopy (XPS). A T-peel test was carried out to evaluate the adhesion strength of the a-C coated PTFE. In the T-peel test, Ar plasma pretreatment improved the adhesion strength more effectively than that of O₂ plasma pretreatment, because of the substantial defluorination and oxygen bonding occurred by Ar plasma pretreatment. Moreover, H-free a-C film reduced the numbers of Escherichia coli (E. coli) colonies dramatically, compared with original PTFE and a-C:H coated PTFE. Consequently, H-free a-C film coating can be a promising method to inhibit the increase of bacteria.