Magnetron sputtering

Magnetron sputtering

In one direction our research group study the fundamental principles of RF-magnetron sputter deposition of calcium phosphate coating as an approach to enhance biocompatibility of metallic and polymer materials applied in regenerative medicine.

Due to the current trend of the population ageing the development of biomaterials for tissues regeneration plays a major role in the field of medical material science. Nowadays, the doctor should have a number of implant systems at his disposal allowing to choose the device for individual patient’s needs to solve any even the most difficult clinical problems. To achieve the favorable implant interaction with the living body the specified interface properties of devices should be created.

As it is considered the interaction between the implant and organism occurs by the aggression path. Human body interprets implant as a foreign substance and tries to get rid of it. The interaction between the cells and tissues with the biomaterials is strongly defined by the tissue-implant interface. The surface properties determine both the biological response to the implants and the material response to the physiological environment. Hence, surface engineering of biomaterials is aimed at modifying the material properties through changes in surface properties meanwhile maintaining the bulk properties of the implant. The application of a biocompatible coating to the implant is a well-documented strategy. Biocompatible coatings must be free from toxic substances, do not cause negative immune reactions, don’t degrade (or degrade in a predictable manner) in contact with living tissues, and show a high adhesion to the implant. Calcium-phosphates are proved to be a natural metabolite of bone. In the field of medical material science, there are numerous studies devoted to increasing of the biocompatibility and osteoinduction of metal implants using calcium phosphate coatings (CaP). Hydroxyapatite (HA, Ca10(PO4)6(OH)2) – is a typical example belonging to the family of CaP materials. As this material defines the bone matrix, it possesses a high biocompatibility.

Radio frequency (RF) magnetron sputtering method is used to obtain the functionally-graded HA thin films. Magnetron sputter deposition is a very attractive method due to the high adherence of the coating to the substrate material, the thickness uniformity of the deposited layer, and the ability to control the coating structure (amorphous or crystalline) and the Ca/P ratio by varying process conditions. Method allows to deposit coatings with predetermined features and to improve the performance of medical implants including devices with complex geometries. In order to develop coatings with additional functional properties there are some studies carried out in the direction of using the modified HA. In particular, we deal with HA material substituted with silver to obtain antibacterial effect and silicate ions to increase coating bioactivity.

Currently, there is no reliable information on the growth mechanisms of CaP based coatings during RF-magnetron sputter deposition. Generally, researchers focus only on the controlling of process parameters to optimize the coating properties in connection with biological studies without investigation of the fundamental aspects of the film growth. This fundamental understanding is the key approach for further technological improvements. This makes it necessary a detailed description of the different processes occurring at the substrate level and an in-depth characterization of the thin film properties. Only the combination of both thin film and plasma characterisation allows to elucidate the growth mechanisms.

Hence, the main objective is the investigation of the fundamental aspects of the deposition of HA coatings by means of RF-magnetron sputtering and the development of strategies to obtain coatings with tailored properties