Photothermal and Antibacterial Properties of Ti-Nb-Zr-Ta Medium Entropy Alloy Thin Films

Abstract

This investigation seeks to elucidate the photothermal conversion characteristics and antimicrobial efficacy of Ti-Nb-Zr-Ta medium entropy alloy coatings with compositionally and microstructurally varied architectures. A suite of Ti-Nb-Zr-Ta MEA coatings was fabricated via magnetron sputtering at oblique incidence angles of 0°, 45°, and 80°. The composition, elemental valence states, phase constitution, and morphology of the films were characterized. Optical absorption and photothermal conversion capabilities were tested, and the biocompatibility and antibacterial properties were evaluated. Results​ The crystal structure of the Ti-Nb-Zr-Ta MEA films was identified as body-centered cubic (BCC). As the incident angle increased, the content of Ti and Nb increased, while Zr and Ta decreased; oxygen content increased, columnar tilting angles increased, structures became looser, and surface roughness increased. Due to the multiple reflection absorption of light by loose columnar crystals and enhanced plasmon resonance resulting from the porous structure, the optical absorption and photothermal temperature rise of the films improved. Under infrared irradiation, the film temperature rose rapidly; the film deposited at 80° reached a maximum temperature of 110°C after 3 minutes of 808 nm irradiation (2 W/cm²). The films exhibited overall antibacterial capability, completely eradicating adherent colonies after 10 minutes of infrared irradiation on the 80° film. The films also demonstrated excellent biocompatibility, allowing fibroblasts to proliferate naturally on their surfaces. Conclusion​ Ti-Nb-Zr-Ta MEA thin films deposited by oblique-angle magnetron sputtering exhibit enhanced photothermal properties due to the "light trap" structure formed by loose columnar crystals, endowing the films with photothermal antibacterial capabilities.