Cu layers sputtered on PTFE: effect of annealing on surface properties and antibacterial activity

This study presents specific properties of Cu layers on polytetrafluoroethylene (PTFE) and their antibacterial effect against two bacterial strains, Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Thin Cu layers were prepared by sputtering on PTFE and subsequently annealed at 300 grad C. Chemical and physical characteristics of Cu layers on PTFE were evaluated before and after annealing employing various analyses. As-sputtered Cu layers exhibited characteristics of metallic copper that were observed as a soar in conductance and surface plasmon resonance band in UV-Vis spectra. Annealing induced the oxidation and rearrangement through Cu layers creating crystalline island structures of CuO. Owing to annealing, PTFE itself was partly exposed and samples exhibited stable hydrophobic character. The nature of antibacterial responses was investigated in relation with the amount of copper and annealing of Cu layers. Bactericidal effect increased with sputtering time and decreased due to annealing. Annealed samples exhibited higher adhesion of Cu layers to PTFE that contributed to a lower bactericidal activity. PTFE sputtered for 400 s demonstrated the highest antibacterial effect against both bacterial strains. (authors)