Flow control using porous magnetic materials

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Our project proposal - Flow control with porous magnetic hybrid materials - in the framework of the SPP 1681 has the goal to develop a magnetic hybrid material whose flow properties can be controlled by an external magnetic field. A hybrid material consisting of shape anisotropic magnetic microparticles and an elastic matrix with channels will be prepared and studied for its magnetic, mechanical, and fluid-mechanical properties. The change of the channel geometry in this material is triggered by tilting the external magnetic field and the associated change in angular position of the particles, which in turn deform the matrix elastically. By changing the shape of the channel cross-section (e.g. from circular to elliptical), a reduction of the hydraulic diameter and consequently an increasing pressure drop can be achieved.External controllability of fluid mechanical properties in such a membrane could have a variety of applications, for example as a separator, or as a part of the separator in a Li-/Na-ion-battery whose permeability e.g. for the transport of ions, need to be limited in the case of excessive heat generation in the battery. This becomes more important the larger the battery stack becomes, e.g. in smart grid devices. Similarly, applications in the field of filtration, for example of drinking water, are interesting. Here, the filter would benefit of two important characteristics of the proposed hybrid material. One hand, one could regulate the hydraulic diameter, and hence the pressure drop across the filter and the volume flow through the filter by using the external magnetic field. Other hand, one could tackle the problem of biofouling, i.e. the progressive accumulation of bacteria and algae species at the inner filter surface by shaking this surface using an external alternating magnetic, so that the adhesion between the deposits and the surface is reduced and they can be transported outside. In a further application, a pumping effect in the channels of the hybrid material could be generated by a changing gradient field, so that there is a transport of liquid through the material.In the first funding period of the SPP, we plan to demonstrate the feasibility of such a novel magnetic actor materials. For this purpose, a comprehensive work plan is proposed, which includes the microscopic, magnetic, and mechanical characterization of the components used and of the final hybrid material. Due to its highly interdisciplinary nature, it is necessary to conduct intensive cooperation with working groups in related fields.