Biocompatible coating and local load-adapted design of additively processed titanium alloys

• Applicants: Dr. Jessica Meißner; Professor Dr.-Ing. Mirko Schaper; Professor Dr.-Ing. Wolfgang Tillmann
• Subject Area: Coating and Surface Technology ; Biomaterials
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 415285024

Based on the results of the joint research project, the proposed interdisciplinary follow-up project aims to develop a customised hip prosthesis made of the additively processed titanium alloy Ti-6Al-7Nb (Ti67) with multi-biofunctional surface areas.The biocompatibility and load-compatible design of the implant are achieved by parameter adjustments in powder bed-based selective laser beam melting (LPBF) to create porous as well as geometrically defined surfaces with subsequent PVD thin films. The systems TiN, TiCN, and a-C:Ag, which were investigated in the first funding period, will be used as thin film material, as they differ fundamentally and allow local adaptation of the surface properties. By adding copper, higher strength, ductility, and anisotropy of the additively processed Ti67 are to be adjusted. In addition, the influence of copper on coatability and biocompatibility is addressed. To adjust the stiffness and surface properties locally, the process parameters of the LPBF process are varied so that areas of different porosity and roughness can be produced. In the additively manufactured hip prosthesis, the femoral head and acetabulum are in tribological contact, so the acetabulum possesses bone-like properties by having a porous inner and dense outer structure, while the ceramic femoral head is attached modularly to the hip stem. Since a mechanical support effect of the substrate material is required for PVD thin films, the extent to which the porous inner structure affects the friction and wear behaviour of the coated Ti67 parts is investigated. The interaction between the surface properties of the additively processed Ti67 and the applied PVD thin films as well as the influence on the mechanical, biocompatible and corrosion behaviour are the focus of the investigations. In the area of the hip shaft, it is expected that the porous structures and defined surface roughness in combination with a PVD thin film will lead to bone cell growth being stimulated while at the same time preventing biofilm formation. To be able to specifically adapt the influence of the thin films on the different implant areas, bioassays (including the establishment of Western-Blot-Investigations for the early characterisation of the influence of the thin film on signalling cascades in the cells) are being established in-vitro. In addition, infection scenarios are planned to simulate and control the influence of thin films on bacterial colonisation. With the knowledge gained, a prosthesis true to reality with defined roughness and porosity, including PVD thin film, will be manufactured and tested close to the application. This will verify and demonstrate the potential of the presented approach.

• DFG Programme: Research Grants