Synergistic Chemical and Topographical Mechanisms for Enhanced Antibacterial Activity in Dual-Phase Thin Films

The urgent need for alternatives to antibiotics has driven significant interest in antibacterial surfaces as potential solutions to combat bacterial infections. In this study, we explore the antibacterial performance of copper-coated dual-phase Zr–V thin films against Escherichia coli. These films were synthesized via magnetron cosputtering of Zr and V targets, resulting in a composition intermediate between purely amorphous and crystalline thin films. This unique composition promotes competitive growth of both phases: the amorphous phase forms smooth columnar structures, while the crystalline phase nucleates and grows as conical features capped by domes exhibiting spiky surface textures. The resulting dual-phase architecture combines a high surface area with pronounced topographical features capable of stretching bacteria and possibly breaking cell walls. When coated with a thin copper layer, these films exhibit enhanced antibacterial activity, benefiting from copper's inherent bactericidal properties. A comprehensive analysis of film topography, ion release rates, and antibacterial testing reveals a synergistic interaction between the chemical and topographical effects. Initially, copper ion release dominates, rapidly eliminating bacteria on the surface. Over time, bacterial adhesion to the spiky surface topography and stretching of the cell membrane further augment the bactericidal effects. This study demonstrates that the engineered dual-phase Zr–V thin films combined with a copper coating provide a promising platform for developing multifunctional antibacterial surfaces with controlled and sustained bactericidal activity.