Microrheology, diffusion, and flow in complex fluids

这项建议是关于凝胶、聚合物、流动颗粒材料和生物流体等材料的实验研究计划，统称为复杂流体。这些材料同时具有粘性(类流体)和弹性(类固体)性质，这是因为它们在长度尺度上具有介于原子尺度和主体尺度之间的结构。例如，聚合物溶液是根据聚合物分子缠结之间的距离来构建的，而我们研究的凝胶由相互作用的微米级颗粒组成。这项建议中描述的一些研究将通过研究小颗粒如何在其中扩散来检查一系列复杂流体的微观结构。这项工作的目标是在微观尺度上了解这些材料中发生的相互作用和过程。我们特别感兴趣的是这些相互作用如何导致微观结构的变化，例如当一种材料经历从流体到凝胶或玻璃的转变时。我们希望将我们对这些相互作用的理解与材料的整体尺度性质联系起来，并最终将其应用于新材料的自下而上设计。我们将对复杂流体中的扩散过程有更好的基础了解，这可能导致改进药物在生物流体中的传输的方法。我们还计划通过使用模仿真实微生物的机械游泳器进行放大模型实验，来研究微生物在生物流体中的游泳。我们还对复杂流体的整体流动行为感兴趣。这项建议中描述的实验将帮助我们了解物体通过这种材料时所受的阻力，以及涉及到海上石油平台的新型锚杆的应用。其中一个实验将研究凝胶中的热驱动对流，对岩浆中的类似流动进行建模，其他实验将研究流动的颗粒状物质。

This proposal is for a program of experimental research on materials such as gels, polymers, flowing granular materials, and biological fluids, collectively referred to as complex fluids. These materials have both viscous (fluid-like) and elastic (solid-like) properties resulting from the fact that they have structure on length scales intermediate between the atomic and the bulk scales. For example, polymer solutions are structured on the scale of the distance between entanglements of the polymer molecules, and the gels we study consist of interacting micron-sized particles. Some of the research described in this proposal will examine the microstructure of a range of complex fluids by studying how small particles diffuse through them. The goal of this work is to understand the interactions and processes that take place in these materials on the microscopic scale. We are particularly interested in how these interactions lead to changes in microstructure, for example when a material undergoes a transition from a fluid to a gel or glass. We hope to relate our understanding of these interactions to the bulk-scale properties of the materials and eventually to apply it to the bottom-up design of new materials. We will develop a better fundamental understanding of the process of diffusion in complex fluids, which may lead to methods for improving the transport of drugs in biological fluids. We also plan to study the swimming of microorganisms through biological fluids by performing scaled-up model experiments using mechanical swimmers designed to mimic real microorganisms. We are also interested in the bulk flow behavior of complex fluids. Experiments described in this proposal will help us to understand the drag force on objects moving through such materials, with applications involving a new type of anchor for offshore oil platforms. One experiment will study thermally driven convective flow in gels, modeling similar flows in magma, and others will look at flowing granular materials.