Flow control using porous magnetic materials

我们的项目提案-多孔磁性混合材料的流动控制-在SPP 1681的框架内，目标是开发一种磁性混合材料，其流动特性可以通过外部磁场控制。将制备由形状各向异性磁性微粒和具有通道的弹性基质组成的混合材料，并研究其磁性，机械和流体力学性能。这种材料中通道几何形状的变化是通过倾斜外部磁场和颗粒角位置的相关变化触发的，这反过来又使基质弹性变形。通过改变通道横截面的形状这种膜中流体机械性能的外部可控性可以具有多种应用，例如作为隔膜，或者作为Li/Na离子电池中隔膜的一部分，其渗透性例如用于离子的传输，在电池中产生过多热量的情况下需要加以限制。电池堆越大，这变得越重要，例如在智能电网设备中。类似地，在过滤领域（例如饮用水）中的应用是令人感兴趣的。这里，过滤器将受益于所提出的混合材料的两个重要特性。一方面，可以通过使用外部磁场来调节水力直径，并且因此调节过滤器两端的压降和通过过滤器的体积流量。另一方面，人们可以解决生物结垢的问题，即通过使用外部交变磁场摇动该表面来解决细菌和藻类物种在内过滤器表面处的逐渐积累，使得沉积物和表面之间的粘附减少并且它们可以被输送到外部。在进一步的应用中，可以通过改变梯度场在混合材料的通道中产生泵送效应，从而使液体通过材料进行输送。在SPP的第一个资助期内，我们计划证明这种新型磁性作用器材料的可行性。为此，提出了一个全面的工作计划，其中包括所使用的组件和最终的混合材料的微观，磁性和机械特性。由于其高度跨学科的性质，有必要与相关领域的工作组进行密切合作。

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.