| Suspension flow dynamics affect the operation and efficiency of many different processes from physiology to industry. The details of fluid behavior depend upon the nature of the constitutive particles as well as on their inter-particle interactions. Research on suspension flow properties often focuses on the effect of these interactions in determining rheological behavior. For instance, short range attractions and electrostatic repulsions impact the development of gels and glassy systems. Both bulk and confined suspensions have macroscopic properties which are determined by microscopic behavior. Many other particle properties, such as surface roughness, asymmetrical shape, and deformability, affect suspension flows. Particle deformability plays an especially important role in physiological systems, for instance mediating healthy functioning in the circulatory system.;The focus of this thesis is on the deformability of particles and its impact on the behavior of suspension flows. Both theoretical and experimental studies were carried out on deformable particle systems. A high-speed optical microscopy set-up was designed and built to investigate and quantify particle dynamics on the microscale. Atomic force microscopy studies were carried out to characterize the deformability of microgel particles used in suspension flow experiments. A theoretical model was developed to describe the effect of particle deformability on the segregation of particles in shear flow and the development of a depleted zone near a wall. These three elements: flow studies, mechanical characterization, and theoretical understanding are each essential, and together can provide an overall picture for the effect of particle deformability on suspension rheology.;Each aspect of the work that follows can be further developed out in its own direction. The optical microscopy technique we have designed provides a method for further investigation into suspension dynamics, and is widely applicable to different types of flows, including emulsions, polymeric fluids, and multicomponent mixtures. The measurements of microgel modulus illustrate rich behavior near a phase transition, which can be explored as function of particle size and chemical preparation. The theoretical work suggests further calculations to enhance its applicability for a wider range of flow types. Furthermore, the synthesis of the work presented here provides insight into applications which may be developed to take advantage of the effects studied. The theory suggests a range of parameters to be explored to investigate elastic separations, design diagnostic devices for specific disease states, and even provide better assessment tools for current medical treatments. |
