Characterization of Tin/Cu Coating on a Niti Substrate Using Rf Magnetron Sputtering Technique: Mechanical, Structural, and Biological Characteristics of the Coating

TiN coatings can be utilized to enhance the surface characteristics of Ti-based implants due to their suitable mechanical and biological properties. However, the occurrence of bacterial infections on the surfaces of coatings creates problems in the development of bacteremia and the spread of infection in the body. Therefore, the addition of a suitable element to TiN coating materials with antibacterial properties is necessary. Among different coating elements with antibacterial properties, Cu shows suitable biological properties and considerable resistance to a wide range of bacteria. In this study, Cu was added to TiN coating to improve its mechanical and antibacterial characteristics. The TiN/Cu films featuring a variety of Cu concentrations were deposited on a NiTi implant substrate using radio frequency (RF) magnetron sputtering. The contribution of copper concentration to the morphology, wettability, and structure was analyzed using a scanning electron microscope (SEM), contact angle analysis, and X-ray diffraction (XRD), respectively. Based on the results, by increasing Cu concentration, the surface becomes more hydrophobic. The antibacterial properties of the coatings were further improved by increasing the Cu concentrations from 2.7 to 6.8 at% against Staphylococcus aureus. The NiTi average hardness was increased from 260 to 400 HV by applying a TiN/Cu coating on its surface with 2.7 at% Cu. However, increasing the copper content in the coatings to 4.11 and 6.8 at%, due to further increase in amount of free Cu, the hardness was progressively decreased to 350 and 320 HV, respectively. The resistance of NiTi substrate to corrosion was significantly improved by coating its surface with TiN/Cu. The optimal corrosion and bioactivity performances were obtained in the coatings containing 2.7 at% Cu, however, the best antibacterial properties occurred in the coatings with 6.8 at% Cu.