A study of the antimicrobial and tribological properties of TiN/Ag nanocomposite coatings

TiN/Ag coatings with varying silver contents have been deposited by pulsed magnetron sputtering. The films were characterised in terms of structure and composition using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The tribological properties of the coatings were assessed by thrust washer wear testing, which showed a marginal reduction in friction coefficient with increasing silver content against a steel counterface. Zones of inhibition were used to determine the extent of silver ion release from the nanocomposite materials, and a NBT (nitro-blue tetrazolium) redox dye was used in an assay to determine the antimicrobial effectiveness of the surfaces following incubation. The microorganisms tested were Pseudomonas aeruginosa and Staphylococcus aureus. Whilst no zones of inhibition were observed on any of the surfaces, for the NBT assays, after incubation, the silver containing coatings revealed a significant reduction in the number of viable cells of both microorganisms, compared to a ‘pure’ TiN surface.