Tribological and antibacterial behavior of Cu doped DLC coatings for biomedical implants

Cu-DLC coatings were deposited on CoCrMo alloys and silicon wafers using magnetron sputtering. Increasing the atomic percentage (at%) of Cu incorporated into the DLC coatings did not significantly alter their overall structure. However, X-ray diffraction results revealed structural differences with increasing Cu content, including larger crystallite sizes and a transition from a predominantly amorphous structure to a nanocrystalline phase. Significant changes in chemical bonding states were observed through Raman and X-ray photoelectron spectroscopy (XPS). Nanoindentation analysis showed reductions in both hardness and elastic modulus, which were inversely correlated with increasing Cu content. Moreover, the wear rate of Cu-DLC showed a greater decrease at 11.8 at% Cu compared to the other coating. Corrosion analysis further indicated that higher Cu content moderated the corrosion inhibition rate. Time course bacterial killing assays demonstrated that Cu contents between 11 and 15.2 at% in the DLC coatings effectively killed both Staphylococcus aureus and multi-drug resistant Klebsiella pneumoniae, with the highest Cu at% resulting in complete bacterial killing at all time points. Overall, incorporation of Cu into DLC coatings enhances corrosion and antibacterial activity with reduced mechanical integrity. An optimal balance between mechanical integrity and antibacterial function can be achieved by carefully controlling the amount of Cu incorporated into the DLC coatings.