Antimicrobial properties of copper plasma-modified polyethylene

Copper plasma immersion ion implantation is utilized to produce an antibacterial surface on polyethylene. XPS analysis of the plasma-treated materials reveals that a relatively large amount of copper, about 11% relative to carbon, is implanted into the near surface region. At the same time, about 3% copper is found to be also deposited on the surface. The implanted copper is observed to have the zero valence state indicating that the implanted Cu does not bind chemically with the atoms in the polymer. On the other hand, the copper atoms close to the surface are found to have the divalent state due to surface oxidation. Formation of CC bonds is also observed due to dehydrogenation following copper plasma implantation. Based on the results of atomic force microscopy and contact angle measurements, the surface hydrophilicity and roughness are not significantly altered. Our antibacterial experiments indicate that the copper implanted polyethylene exhibits excellent antibacterial effects against Escherichia coli and Staphylococcus aureus, and the effectiveness is 96.2% and 86.1%, respectively.