Energy efficiency and sustainability encourage to develop lightweight materials with excellent mechanical properties, combining also additional functionalities and responses. Therein nature allows inspiration, as e.g. pearl of nacre and silk show extraordinary mechanical properties due to their aligned self-assemblies. However, biological complexity poses great challenges and in biomimetics selected features are mimicked using simpler concepts. Previously artificial nacre has been mimicked by multilayer and sequential techniques and ice-templating. However, concepts for aligned spontaneous self-assemblies are called for scalability. We will develop toughened nacre-inspired materials by templating functionalized polymers on colloidal sheets in suspension, followed by self-assembly by solvent removal. Similarly, we will develop silk-mimetic materials using aligned organic fibrous reinforcements in soft dissipative matrix. Nanofibrillated cellulose will be wet-spun using extrusion into coagulant bath, followed by post drawing, drying and functionalization to allow silk-like fibers with high mechanical properties. In another route, cellulose rod-like whiskers will be decorated with soft functional polymers allowing energy dissipation, followed by alignment and interlinking to mimick silk-assemblies. The colloidal routes allow also new functionalities by using functional polymers, e.g. electroactive and conjugated polymers and nanoparticles. Importantly, redox-active polymers are bound on the colloidal sheets. Incorporating in a planar electrochemical cell with flexible electrodes, electrochemical switching of stiffness is obtained using a small voltage, as the intercolloidal interaction is controlled by the charge state of the redox-active layers. This would allow a new class of material, eg. to interface users and devices. In summary, we present a colloidal self-assembly platform for biomimetic materials with exciting mechanical, functional, and switching properties.
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