High-Performance Biocompatible Ag-DLC Coatings - Precise and Localized Silver Doping Through Novel Helium Pulse Injections

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Diamond-like carbon (DLC) coatings are renowned for their excellent mechanical properties and biocompatibility. The overall DLC market is projected a compound annual growth rate (CAGR) of 14% by 2020, while the DLC in biomedical sector alone is growing with a CAGR of 33%, which is inspiring advanced DLC research for biomedical use. Hard DLC coatings have poor toughness which limits their application for joint implants that involve impact, shear, and torsion. Silver-doped DLC coatings (Ag-DLC) are increasing in popularity in the biomedical sector as they boost biocompatibility and toughness of pure DLC coatings simultaneously. The biocompatibility of Ag-DLC is shown to increase by increasing Ag fraction, but excessive Ag reduces the mechanical strength and durability and a high Ag dose may become toxic to the patient if the coating fails. We have identified that Ag is essential for early post-surgery, thus it would be highly beneficial to develop a coating where Ag is only doped near the surface, providing maximum biological performance without reducing DLC strength. In fact, selective Ag doping in a DLC matrix is challenging through established physical vapour deposition techniques. In this project, we are aiming to develop a novel DLC coating with precise and localized doping of Ag nanoparticles using the sputtering method. The Ag nanoparticles will be created in-situ by rapid plasma quenching with He pulses and simultaneously embedded in the DLC matrix in a single-step process. The unique features are precise amounts and specific size of Ag nanoparticles which will be embedded at controlled depths in the DLC matrix. The coatings will be tested for biological functioning i.e., biocompatibility and antimicrobial tests and mechanical performance, which includes hardness, toughness, and tribology. The new Ag-DLC coatings are expected to present a simultaneous improvement in biological and mechanical performance due to their unique tailor-made architecture.