Microrheology, diffusion, and flow in complex fluids

本提案是针对凝胶、聚合物、流动颗粒材料和生物流体等材料的实验研究项目，这些材料统称为复杂流体。这些材料具有粘性（类流体）和弹性（类固体）特性，这是因为它们具有介于原子尺度和体尺度之间的长度尺度结构。例如，聚合物溶液的结构是基于聚合物分子缠结之间的距离，我们研究的凝胶由相互作用的微米大小的颗粒组成。本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。这项工作的目标是在微观尺度上理解这些材料中发生的相互作用和过程。我们对这些相互作用如何导致微观结构的变化特别感兴趣，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体积尺度特性联系起来，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一个更好的基本理解，这可能会导致改进生物流体中药物运输的方法。我们还计划通过使用机械游泳器模拟真实微生物进行放大模型实验来研究微生物通过生物流体的游泳。我们也对复杂流体的整体流动特性感兴趣。本提案中描述的实验将帮助我们理解物体在这些材料中移动时的阻力，其中包括一种用于海上石油平台的新型锚。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.