Diffusion of Particles and Photons in Complex Fluids

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w:\awards\awards96\*.doc 9623441 Yodh This experimental research project in condensed matter physics will study particle dynamics in colloidal suspensions and diffusing photon dynamics in highly scattering or turbid media. These studies of colloids center around new ideas for the control of colloidal particle motion. In particular, traps and templates for particles on substrates will be created by carefully constructing free energy barriers. These free energy barriers are brought about as a result of entropy effects in the suspension. Photon transport investigations will center on the fundamental properties of highly scattered light. In particular the research will study how material anisotropy, and fluctuations are impressed upon photon electromagnetic fields that diffuse through turbid media in a manner similar to heat flow. %%% Careful study of light beams passing into highly scattering or turbid materials has revealed a variety of interesting phenomena and applications. Light diffuses through these substances in a manner similar to heat flow. As a result of our increased knowledge about these processes diffusing light can now be used to generate low resolution images of absorption or scattering variations within human tissues and in other complex, opaque media. One goal of this proposal is to develop an improved fundamental understanding of these processes, and to further develop the instrumentation required to exploit these phenomena, so that more diverse applications are possible. A secondary goal of this proposal is to create new materials based on particle suspension that may be of use in the topical field of photonics. ***