Colloidal Fluids Wetting Solid Surfaces

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CTS-0100854Darsh Wasan, Illinois Institute of TechnologyIt has been shown previously that in the presence of colloidal particles, the wetting region is comprised of the bulk fluid with the meniscus and the transition region leading to a thin film of structured colloidal particles. Experiments with similarly charged monodispersed latex particles show co-existence of ordered-disordered particle structures, depending on the film thickness relative to the particle diameter. Since the particles are similarly charged, there must be some form of long-range attractive force responsible for creating the ordered structure. Microintereferometric methods are proposed to be used to measure the film thickness profile and to calculate the capillary pressure near the contact line. The effect of volume fraction, particle size, shape and polydispersity on the film structure and stability will be investigated by direct observation of the ordered microstructure within the thin film near the contact line. The structural disjoining pressure will be calculated from the particle radial distribution function and the mean potential of particle interactions. The contact angle is calculated from experimentally measured values of the capillary pressure and the calculated disjoining pressure.