Rheology of biocompatible ferrofluids in blood

磁性颗粒悬浮液在生物医学上的应用，特别是在癌症治疗方面的应用，在过去几十年中引起了越来越多的兴趣。在这种情况下，基础研究表明，特别是通常称为磁性药物靶向的方法的流体力学方面，即对肿瘤区域的磁控制递送，仍然需要澄清许多基本方面。在这方面特别感兴趣的是在磁场存在下各自悬浮液的粘性行为的变化，这是澄清基本流体力学问题所需要的。初步实验表明，即使在弱磁场中，生物相容性铁磁流体的粘度也会显著增加，同时其流动行为也会发生变化。这是由于在这种具有强磁矩的生物相容性铁磁流体中存在相当大的磁性颗粒团，从而产生强的粒子间相互作用。初步调查还表明，即使用水或血液稀释液体，所观察到的影响仍然存在。因此，该项目的中心目标是澄清血液中磁性颗粒悬浮液的流变学，即详细了解医疗应用中存在的这些混合物的流动行为。在毛细管流变实验中，可以应用毛细管流变学研究在大范围的场强、剪切速率和流体组成下的流变行为。这些研究的最终目标将是为这些悬浮液在磁场中的流动行为建立一个本构物质定律，这将允许模拟生物医学应用。

The use of suspensions of magnetic particles in biomedical applications - especially in cancer therapy has attracted growing interest in the past decades. In this context basic investigations have shown, that especially the fluid mechanics aspects of an approach commonly called magnetic drug targeting, i.e. a magnetically controlled delivery towards a tumor zone, still require the clarification of numerous fundamental aspects. Of particular interest in this respect are changes of the viscous behavior of the respective suspensions in the presence of magnetic fields that are needed for the clarification of basic fluid mechanical questions. Preliminary experiments have shown that biocompatible ferrofluids show a significant increase in their viscosity accompanied by the appearance of changes in their flow behavior even in weak magnetic fields. This is forced by the fact that comparably large clusters of magnetic particles exist in such biocompatible ferrofluids exhibiting a strong magnetic moment, which gives rise to strong interparticle interaction. The preliminary investigations have moreover shown that the observed effects subsist even if the fluids are diluted with water or blood. Thus, it is the central objective of project to clarify the rheology of suspensions of magnetic particles in blood, i.e. the flow behavior of those mixtures present in medical applications in detail. It is foreseen to investigate the rheological behavior over a wide range of field strength, shear rate and fluid composition in rheological experiments using capillary rheology. The final goal of these investigations will be the establishment of a constitutive material law for the flow behavior of such suspensions in a magnetic field, which will allow simulations of biomedical applications.