Push, Push, Push – Cooperative Actuators and Actuators Fields by Direct Writing Pro-cesses

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Two-photon crosslinking (2PC) based on C,H insertion reactions allows the generation of microactuators from magnetic composites by a maskless direct writing process. To this copolymers are employed in which 2-photon chromophores such as suitably substituted anthraquinone groups are incorporated and which are cross-linked with the aid of 2-photon processes. This cross-linking process takes place in the glass-like state of the polymers. After completion of the writing process, all non-crosslinked polymer molecules are washed out to develop the microstructures. If nanoparticles have been mixed into the prepolymers before the deposition of the layer, three-dimensional microstructured nanocomposites can be obtained directly in a one-step process. Thus, with the help of such a maskless writing process, magnetically actuatable microstructures in almost any form can be written three-dimensionally which are self-supporting. In the proposed project, cooperative magnetically actuatable structures such as ciliated surfaces for micromixers or micropumps or actuator fields which show metachronal waves will be generated. By variation of the written structures, actuator fields with designed properties or actuators, which can act cooperatively can be generated. Larger structures can be generated by molding with the same polymers, but by a conventional photochemical process and/or 3D printing.Furthermore, it will be investigated to what extent microactors can be generated by writing network structures in multilayers in which the actuators react to different stimuli. For this purpose multilayered systems are generated from different materials and after drying they are cross-linked in a glass-like state by means of the two-photon process, so that the individual structural components are covalently linked to each other. In this way, actuators are obtained in which parts of the structures can be influenced either gradually or switched on/off by an external stimulus, for example light or moisture. Thus, microactuators can be generated that allow intrinsic sensing and an autonomous response to changes in the environment. If these multi-responsive actuators are skillfully combined, a multi-stage actuator system should be achievable in which the respective stage is reached by an external stimulus. On the other hand, looking at actuator fields the individual parts of the cilia fields could be switched on and off by the external stimulus, so that novel cooperative phenomena can be investigated.The proposed project will also investigate how bi- and multistable structures can be generated using the newly developed method. For bi-stable structures, actuators have to be designed where the system can be switched from one stable state to another by a simple "snap through" mechanism or showing other buckling instabilities.