The tribological protection of carbon fiber reinforced epoxy composites (CFC) is essential for broadening their use from structural to functional applications, e.g., to linear bearings in mechanical engineering. However, their wear resistance in sliding and rolling contacts is low. This work focusses on the possibility of improving their tribological properties by the application of thin hard multi-layered coatings. Chromium nitride (CrN) single layer and chromium-CrN multilayer coatings of ~4 µm thickness, partly finished with a 1 µm diamond-like carbon (DLC) top layer, were deposited by magnetron sputtering at low temperatures on soft CFC and for comparison of the mechanical behavior on comparatively hard austenitic steel substrates. Structural investigations showed especially that the multilayer coatings possess a very fine grained, columnar microstructure and a very low density of intercolumnar micro-cracks, while the single layer coatings possess a coarse structure. The indentation testing and the analysis of the deformed and fractured cross-sections revealed a tougher behavior with improved plastic deformability of the multilayers in comparison to CrN single layers. However, in wear testing only coatings with DLC top layers significantly improved the tribological material properties of CFC. This is due to the reduced shear forces in sliding on low-friction DLC coatings on the soft epoxy-based CFC, decreasing the total dynamic stresses during sliding under high loads.

The functionalization of biomaterials for implants becomes increasingly important for designing bioinert and bioactive surfaces to reduce the impact of implantation to human body (inflammation, encapsulation) and extend the lifetime of implants. Even pharmacological effects can be triggered by nanomaterials like thin films and nanoparticles in medical treatment. However, the systematic knowledge of the interactions between cells and artificial, inorganic materials is poor yet. Finding the decisive influences for high hemocompatibility or osseointegration is very difficult. Surface chemistry including wetting behaviour, surface charge, homogeneity and functional groups as well as surface topography are some of the fundamental surface parameters defining the cell–surface interaction. Focusing on physical and chemical vapour deposited thin films and coatings, this review will provide for a better understanding of biocompatible coating materials like titanium- and carbon-based compounds and calcium phosphates.

Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials.

The potential of the combination of hard and soft coating on elastomers was investigated. Diamond-like carbon (DLC), molybdenum disulfide (MoS₂) and composite coatings of these two materials with various DLC/MoS₂ ratios were deposited on four elastomeric substrates by means of the magnetron sputtering method. The microstructures, surface energy of the coatings, and substrates were characterized by scanning electron microscopy (SEM) and contact angle, respectively. The chemical composition was identified by X-ray Photoelectron Spectroscopy (XPS). A ball on disc configuration was used as the model test, which was performed under dry and lubricated conditions. Based on the results from the model tests, the best coating was selected for each substrate and subsequently verified in component-like test. There is not one coating that is optimal for all substrates. Many factors can affect the coatings performance. The topography and the rigidity of the substrates are the key factors. However, the adhesion between coatings and substrates, and also the coating processes, can impact significantly on the coatings performance.