Rheology of Complex Fluids at High Shear Rates using Scattering and Microfluidic Rheometry

Structure-property relationships of fluids may be governed by self-association behavior influenced by flow. We developed microfluidic methods to minimize fluid volumes, to test high shear rates (up to 1 000 000/s), and to obtain simultaneous measurements of viscosity and structure. For fd-virus solutions and wormlike-surfactant solutions we measure alignment, form and structure factors, and we interpret these results in light of rod-like scattering models, in an effort to understand length distributions of the surfactant solutions. A high degree of alignment is observed over a wide range of shear rate; at intermediate rates, wormlike solutions exhibit semidilute behavior and at higher rates dilute behavior is observed, and we relate this change to differences in structure. For protein solutions, we measure aggregation of protein particles during flow past surfaces of controlled surface chemistry, to which protein adsorbs.