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Keywords: Brownian rods, surfboards, drug delivery, capsules, vesicles, margination

Abstract: Many dispersions of colloidal particles with application in materials processing, biological assays, or medicine, contain elongated particles (e.g. ellipsoidal disks, rods, etc.) Recently these particles have been used in drug delivery applications because of the inability of leukocytes to easily rid them from the circulation. Moreover such particles are useful at the nanoscale for application in cancer therapies, either for detection of tumor vasculature or for the delivery of anti-cancer agents to tumor endothelial cells. Thus, the study of anisotropic particulate flows with adhesion in microchannels especially in mixtures with vesicle flows (i.e. red blood cells) has taken on a particularly important set of engineering applications. In order to understand the transport in these systems, a numerical simulation must include: a) a high fidelity representation of nonequilibrium dynamics of vesicles and capsules in microflows, b) the dynamic simulation of Brownian colloidal particles of general shape in microflows, and c) the combination of these in mixtures at finite concentration. Each of these transport processes brings in new physics which we will review. In discussing a) we will focus on the transition between tank-treading, tumbling, and trembling dynamics in flow and whether these transitions also happen at finite concentration in microfluidics. In b) we will discuss the particle concentration distribution of Brownian nonspherical particles in microfluidic flows and its relation to the nonequilibrium osmotic pressure. In c) we will examine how particle margination in mixtures occurs and how it is related to the concentration of vesicles/capsules in the microflow. Ultimately, we will look toward the virtual prototyping and engineering of these therapies.