RF-magnetron sputter deposited hydroxyapatite-based composite & multilayer coatings: A systematic review from mechanical, corrosion, and biological points of view

Till date, a variety of efforts have been made to develop the essential properties of hydroxyapatite as the most promising bioactive ceramic used in a broad spectrum of clinical applications from bone-tissue engineering to the bio-coatings applied on the implants. Radio frequency magnetron sputtering provides multiple advantages including high efficiency, favorable bonding strength, and controllable properties, therefore an increasing tendency has been emerged for exploiting its benefits in fabrication of HAp bio-coatings. The present review strives to systematically address all of the reported results in the field of RFMS'ed HAp-based composite and multilayer bio-coatings with putting the stress on drawing a clear correlation between the assessed variables, e.g. chemical composition and content of reinforcing phase(s) and interlayer(s), operating conditions, pre/post treatments, and the final characteristics of the bio-coatings. The facing challenges and future horizons of these systems are also treated in detail.