Nanomechanical characterisation of multilayered organic-inorganic composite films produced by bioinspired processing routes

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This project aims at the nanomechanical investigation of organic-inorganic composite films synthesised via an established bioinspired route. A major goal is to impart superior mechanical properties on these biomimetic molecular architectures by the implementation of nature-derived molecular design principles. The envisioned composite films shall be fabricated on various types of surface-modified substrates through alternating layer-by-layer assembly of metal oxides as inorganic and charged polymers as organic components. While in the first stage of the project, titanium dioxide layers formed via low-temperature chemical bath deposition will be chosen as inorganic component of the multilayers, the investigations will then be extended to layers composed of vanadium oxide nanofibres with ultra-high aspect ratio. For the assembly of the latter type of layers, two deposition approaches will be used, in which either pre-formed fibres are adsorbed onto the surface, or the fibre growth is nucleated at suitable chemical surface sites. To investigate the mechanical properties of the composite films, nanoindentation and nanoscratch tests shall be employed, in order to determine hardness, Young s modulus, fracture toughness as well as the adhesion strength of the layers to the substrate. For this purpose, different procedures for analysing the nanoindentation/nanoscratch data will be critically evaluated with respect to their ability to cope with possible complications such as surface roughness and the influence of the substrate. On that basis, the importance of the multilayered architecture will be evaluated by comparing the nanoindenation data with those obtained from oxide monolayers as reference. Further to this testing, extensive structural characterisations will be made to enable a detailed correlation between the multilayer morphology/composition and their mechanical performance.