3D measurement of field-induced deformations in magnetic hybrid materials

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The aim of the last funding period of this proposal is to measure the internal deformation in magnetic hybrid materials for systems that are close to real world systems. This information will be used to obtain a well-founded understanding of this class of materials. The methods used are a continuation and further development of those used in the first two founding periods. Using optical microscopy techniques (transmission and confocal microscopy), we determine the trajectories of magnetic particles and tracer particles in the material. This will allow us to deduce the deformation fields and other internal data. Specifically, we intend to 1. characterize precisely the matrix-mediated interaction between magnetic particles. Here the goal is not only the interaction itself, but also the underlying deformation field that can be determined with confocal microscopy. 2. use this interaction, to induce large deformations in the material. This will be done with periodically structured systems that allow for collective effects which enable a larger response of the system to an excitation. 3. measure the deformation field between a few magnetic particles under the influence of an applied magnetic field. Here, we especially aim at a comparison of different length scales, e.g., in collaboration with the Odenbach group. 4. investigate the influence of finite frequencies of the magnetic excitation. Most materials used as matrix materials of magnetic hybrid materials are viscoelastic. This is a strong hint that the magneto-mechanical effects depend on frequency. We intend to investigate these effects. 5. determine specific modes of material failure in magnetic gels. The displacement of magnetic particles in the magnetic hybrid material leads locally to very strong deformations. Do these strong deformations lead to a failure of the material under repeated loading? 6. analyse the influence of free or rigid boundaries on the internal mechanisms. Not only particles in the interior of the magnetic hybrid material influence each other, also surfaces nearby will change the internal dynamics. None of the work packages in this proposal can be dealt with separately. All work packages are connected within this proposal and, more importantly, to other projects.