(498c) The Effect of Particle Characteristics on the Hydrodynamic Separation of Binary Systems

When flowing in small, confined channels, emulsion droplets and other suspended materials migrate across the flow direction due to a combination of effects like hydrodynamic diffusion and wall migration. The phenomenon known as margination is observed in multicomponent suspensions such as blood: plasma, leukocytes, and white blood cells flow near the walls of a channel while large, deformable red blood cells congregate in the center. Although the segregation of red blood cells is well known, interactions between other particle types is experimentally understudied, with most work having been done computationally. The trajectory of particles is determined by particle properties including size, deformability, and surface chemistry along with flow properties such as shear rate. Given the large number of control parameters, there is a rich parameter space to explore the phenomenon of passive, cross-stream separation. For instance, a better understanding of particle hydrodynamics in complex systems will help to elucidate design principles for drug delivery vehicles entering the bloodstream, and may also improve our understanding of the immune response in blood flow, in which leukocytes interact with and remove foreign bodies.

In this presentation, we investigate the flow of a multicomponent system model. We begin by studying binary suspension flows to determine the effect of size ratio, deformability, and surface charge on species separation in a microchannel. Video microscopy data is then collected by flowing suspensions and tracking particle trajectories and concentration profiles for each species. By investigating emulsion drops and liposomes, we study two different mechanisms of deformability: droplet deformation due to surface tension and liposome deformation through membrane bending. We investigate the importance of the size ratio by making liposomes that are both larger and smaller than the emulsion droplets. The surface charge of liposomes is controlled using the respective lipid while the surface charge of droplets is controlled through the addition of surfactants. Studying binary systems with differences in particle size, surface charge, and deformability will help to further understand the properties that control particle dispersion in multicomponent systems.