Picosecond Laser Treatment of Cu-Doped TiO2 Coatings: Effects on Mechanical Resistance, Electrochemical Behaviour, and Antibacterial Activity

Implant-associated infections remain one of the leading causes of failure in orthopaedic and dental implants, necessitating the development of multifunctional surface coatings capable of simultaneously enhancing corrosion resistance, bioactivity, and antibacterial performance. The aim of this study was to investigate how picosecond laser surface treatment modifies the structural, physicochemical, mechanical, electrochemical, bioactive, and antibacterial properties of magnetron-sputtered TiO2/CuO coatings on Ti6Al4V alloy. Structural characterisation revealed that laser treatment transformed the predominantly amorphous TiO2 matrix into a more crystalline rutile-containing structure while preserving the CuO phase. The laser surface-treated (LST) surface exhibited increased surface hydroxylation, enhanced wettability, and a slightly higher release of Cu ions. In addition to modifying the surface chemistry, laser treatment improved the mechanical characteristics of the coating, contributing to its overall durability and suitability for biomedical implant environments. Electrochemical impedance spectroscopy demonstrated that both coatings significantly improved the corrosion resistance of Ti6Al4V in simulated body fluid, whereas the laser-treated coating showed superior long-term stability and passive layer evolution. Following immersion, both surfaces promoted the formation of Ca–P-rich hydroxyapatite deposits, indicating favourable bioactivity. Antibacterial testing against Staphylococcus aureus revealed reductions in bacterial viability of 67% and 74% for the AD and LST coatings, respectively. The enhanced antibacterial performance of the laser-treated surface was attributed to the combined effects of increased crystallinity, surface hydroxylation, hydrophilicity, and copper ion release. The novelty of this work lies in demonstrating that picosecond laser post-treatment can simultaneously tailor the crystallinity, surface chemistry, morphology, corrosion resistance, bioactivity, and antibacterial performance of magnetron-sputtered TiO2/CuO coatings without compromising coating integrity, thereby providing a promising multifunctional surface modification strategy for biomedical implants.