Tuning the antimicrobial behaviour of Cu85Zr15 thin films in “wet” and “dry” conditions through structural modifications

The antimicrobial behaviour of Cu85Zr15 at. % thin films prepared by magnetron sputtering was studied in both wet and dry conditions. Small variations in key deposition processing parameters (pressure and substrate temperature) enabled the growth of thin films with similar nanostructures but different degrees of compactness, according to the Thornton’s structural zone model. This model has proven its effectiveness in providing sensitive structural information to explain significant differences in antimicrobial behaviour of the CuZr thin films, even when processing conditions lie within the same structural zone. The antimicrobial behaviour has been studied for E. coli and S. aureus for up to 4 hours of “dry” contact. Structures of lower compactness, grown at higher deposition pressure, are shown to provide higher antimicrobial activity for “dry” conditions than for “wet” conditions. For thin films of CuZr deposited at 0.5 Pa, the reduction percentage of bacteria is 99.47 %, which is much higher than the results of 70-80 % obtained for the films deposited at 0.1 and 0.3 Pa. Microscopy studies indicate that for 4 hours of contact time, bacteria exhibit inner damage and even lysis, however, no morphological changes are detected because of the short timeframes used.