Optimizing microstructure and properties of Zn-modified titania films via ultrasonic-assisted micro-arc oxidation: The critical role of ZnO concentration

Zn-modified titania, as a promising biomaterial for orthopedic implants with enhanced osteogenic properties, could be fabricated via ultrasonic-assisted micro-arc oxidation (UMAO) in electrolytes containing ZnO nanoparticles (NPs). The present work systematically investigates the influence of ZnO content (2, 5, and 10 g/L) on the microstructure, corrosion resistance, and in vitro biological performance of Zn-modified titania. Microstructural characterization reveals that 2 g/L ZnO yields a uniform film surface due to the deposition detachment, whereas films with 5 and 10 g/L ZnO retain partially-crystallized hydroxyapatite (HA) depositions connected to the underlying TiO 2 via nano-sized fusion bands. The structural evolution is attributed to ultrasonic assistance (UA), where its thermal effect promotes fusion while its mechanical effect governs deposition detachment. Electrochemical measurement suggests that the film with 10 g/L ZnO addition possesses enhanced corrosion resistance compared to other variants, mainly ascribed to the pore-sealing effect of HA depositions. For biological performances, the film with 10 g/L ZnO addition demonstrates an antibacterial rate of ∼84.89% against S. aureus bacteria , which also significantly enhances MC3T3-E1 osteoblast proliferation and differentiation. Therefore, our present study elucidates the formation mechanism of Zn-modified titania, providing critical insights for optimizing bioactive ceramic films for orthopedic implant applications. • A ZnO concentration threshold (≥5 g/L) facilitates HA deposition, which is securely anchored by interfacial fusion bands to avoid detachment. • Ultrasonic cavitation effect promotes HA formation with ZnO NPs as preferential nucleation sites. • The bioactivity of Zn-modified titania film is enhanced by both incorporated Zn and deposited HA.