Microstructural and tribological properties of TiO2/Ag multilayer coatings using magnetron sputtering technique for potential applications in non-permanent implants

Abstract

The development of ideal surfaces for metal implants and osseous stabilization devices requires consideration of various phenomena. These include the formation of bacterial biofilms on the surface, which can lead to infections or rejection of the device. Additionally, the overgrowth of bone material around these devices can create a barrier to their removal once their function has been fulfilled. Due to this, the development of multilayer antibacterial coatings of TiO2/Ag on Ti6Al4V substrates was studied for potential use in non-permanent implants. Magnetron Sputtering technique, which provides significant control over the microstructural features was used to deposit 10 and 15 TiO2/Ag bilayers, resulting in coatings with a uniform and packed structure. Additionally, TiO2 monolayer was used as a comparative sample. Consequently, the properties of the developed systems were characterized using scanning electron microscopy/energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, tribologic assays and surface properties such as rugosity and wettability. Experimental results confirm the presence of crystalline anatase in all systems and an increase both in thickness and roughness as the bilayer number increases compared to TiO2 monolayer coatings. Multilayer coatings evince decreased wettability and crystallinity with higher bilayer counts compared to the highly hydrophobic nature of Ti6Al4V substrates (>90°). Both systems, 10 and 15 multilayer coatings present a thickness of approximately 730 nm and improved hydrophilicity with contact angles of 68.5° and 55.2° respectively, while the TiO2 monolayer grew around 1300 nm and had a contact angle of 86.3° Finally, the tribological properties improve as the silver content on the surface increases as the noble metal tends to accumulate in nanoparticles on the outermost layers of the multilayer systems, exhibiting its solid lubricating effect, however, the wear rate increases for 15TiO2-Ag sample, as more Ag migrates, altering the coating microstructure.