Microrheology, diffusion, and flow in complex fluids

点击翻译按钮获取中文摘要

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.