Microrheology, diffusion, and flow in complex fluids

该建议是对凝胶、聚合物、流动颗粒材料和生物流体等统称为复杂流体的材料进行实验研究的计划。这些材料具有粘性（类流体）和弹性（类固体）性质，这是由于它们具有介于原子尺度和体积尺度之间的长度尺度上的结构。例如，聚合物溶液的结构是以聚合物分子缠结之间的距离为尺度的，我们研究的凝胶由相互作用的微米级颗粒组成。该提案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。这项工作的目标是了解微观尺度上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，例如当材料从流体转变为凝胶或玻璃时。我们希望将我们对这些相互作用的理解与材料的大规模性质联系起来，并最终将其应用于新材料的自底向上设计。我们将开发一个更好的基本了解的过程中的扩散复杂的流体，这可能会导致改善药物在生物流体中的运输方法。我们还计划通过使用旨在模拟真实的微生物的机械游泳者进行放大模型实验来研究微生物在生物液体中的游泳。我们还对复杂流体的整体流动行为感兴趣。在这个建议中描述的实验将帮助我们了解物体移动通过这种材料的阻力，与应用涉及一种新型的海上石油平台的锚。一个实验将研究凝胶中的热驱动对流，模拟岩浆中的类似流动，其他实验将研究流动的颗粒状材料。

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.