Flow of colloidal and living suspensions in confined geometries

Abstract

We study the role of geometric confinements on the flow of colloidal and living through experiment, simulation, and scaling theory. In the first project, we explore the dynamics of a propagating clogging front comprised of colloidal particles confined to two-dimensional microfluidic channels with leaky boundary conditions. We found using a combination of experiment, simulation, and scaling theory that because of the leaky boundary condition, clogs propagate backwards against incident flow with a stationary wedge-shape and that the speed of the jamming front is consistent with simple mass balance. In the second project, we confined a dense suspension of motile \textit{Escherichia coli} (\textit{E. coli}) within the thin spherical shell of a double emulsion droplet and studied collective azimuthal flows as a function of droplet curvature and \textit{E. coli} activity (motility). We experimentally discovered and confirmed with simulation that these systems exhibit azimuthal zonal flows which oscillate between counterclockwise and clockwise circulating states with persistence statistics which depend on the double emulsion size.