Soft matter: complex transport processes and micro-mechanics

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My research program has recently made several important contributions to understanding complex transport processes that take place in polymeric composites. Firstly, for hydrogel composites (where charged colloidal particulates are immobilized in uncharged hydrogel matrices), we have established a rigorous theoretical foundation for advancing novel diagnostic techniques that may, in the longer term, sense biomolecular reactions in hydrogel composites, monitor cell metabolism in immobilized tissue cultures, and facilitate the early detection of breast cancer. In this work, we will develop model experimental systems to demonstrate quantitative links between laboratory measurements and physicochemical characteristics of the nanocomposite microstructure. Secondly, for polymeric nanocomposites (where nanoparticulates are dispersed in polymer melts and glasses), we developed an original theory that successfully quantifies how impenetrable nanoparticles unexpectedly enhance the permeability and reverse selectivity of glassy membranes used for gas separations. To predict membrane performance under industrially relevant conditions, we will extend the present theory to compute nanoparticle clustering, which, in turn, will be used to predict membrane permeability and selectivity at high particle loadings. My research program has also successfully applied electro-kinetic theory to develop hypotheses concerning the dynamics and organization of polymers grafted to the surfaces of phospholipid membranes. Because the polymer dynamics play an important role in laboratory diagnostics, and influence the stability and effectiveness of liposomal drug formulations, we will experimentally test our hypotheses by directly imaging polymer-derivatized phospholipids while under the influence of electrical and hydrodynamic shear forces. Finally, we will develop a theory to elucidate the propensity of polymeric nano-tubes to spontaneously buckle and fold. This research will couple theory and micro-mechanical testing, using a sophisticated optical tweezers apparatus my group has recently built, to devise practical strategies for controlling the synthesis and assembly of nanotubes for biosensing and nanofiltration applications.