Multifunctional Layered Magnetite Composites

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In natural organic-inorganic composites such as nacre, stiff and hard but brittle inorganic crystals are joined together by soft and ductile organic materials. Due to a sophisticated hierarchical structuring and a well controlled coupling at the interface between the two components, these biological structures combine both stiffness and toughness. Another example are chiton teeth which are extremely wear resistant through a hybrid design of magnetite nanoparticles embedded in a polysaccharide-protein gel matrix. Inspired by these 3 materials design concepts, we aim to develop biomimetic composite structures that are based on the insoluble matrix of natural nacre as scaffold which is filled with a gelatin gel as mimic for the natural silk hydrogel. In this matrix, magnetite nanoparticles will be synthesized with and without the control of nucleator peptides derived from studies of proteins responsible for magnetite synthesis in magnetotactic bacteria to take advantage of the genetic control over the magnetite nucleation in these organisms. With the goal of a high mineral content and performing the synthesis in a magnetic field, the magnetite nanoparticles shall be co-aligned leading to coupling of the magnetic dipoles depending on the particle size as a three dimensional mimic of the magnetite nanoparticle chains in magnetotactic bacteria. Simultaneously, the nacre-like structure combined with the structural mimic of chiton teeth could lead to fracture resistant as well as wear resistant materials coupled with interesting magnetic properties due to the coupling of the magnetic dipoles. Via the polymer concentration adjustable network structure of the gelatine gel and the magnetite content, we aim to control the mechanical properties of the composite material. We hope to develop a material which combines the best of the properties of three different biominerals by structural design: The fracture toughness of nacre, the wear resistance of chiton teeth and the magnetic properties of co-aligned magnetite nanoparticles in magnetotactic bacteria. The structure and propertes of these materials shall be characterized by Neutron and X-ray scattering as well as other methods and the structural materials design will be supported by computer modelling.