UC Berkeley

This dissertation is an attempt to address open questions in the area of suspension migration behaviors that have been observed. Different flow regimes and their corresponding migration behaviors are introduced, and the lack of experiments investigating the collective migration behavior of deformable particle or vesicle suspensions is discussed. One of the reasons for this gap in the literature is the absence of readily available, well-controlled vesicle suspensions (or another model deformable particle suspension). Vesicles are attractive to study because their dynamic behavior in flow is similar to that observed for cells of interest (e.g. red blood cells), but most vesicle generation methods produce very polydisperse vesicle suspensions – or suspensions with a broad distribution of vesicle diameters. The development of a protocol for reduced-polydispersity vesicle suspensions involves a parametric study of electroformation as a vesicle generation method, as well as the application of microfluidic separation technologies, originally developed for suspensions of particles and cells. Because the resulting vesicle suspensions still exhibit some polydispersity, migration experiments are performed with a bidisperse suspension of rigid spherical particles to gain insight into the effect of polydispersity on migration behavior. Initial results indicate that even in dilute conditions, particles in mixed suspensions exert some influence over each other. Differences are observed when comparing migration lengths of particles in bidisperse suspensions to migration lengths of particles in monodisperse suspensions. Potential next steps and challenges to conducting migration experiments with vesicle suspensions are discussed.