(373h) Dynamics of Colloid-Polymer Suspensions in Confined Systems and on Structured Surfaces

We will present experimental studies of the behavior of colloid-polymer suspension near interfaces, with a focus on depletion-induced interactions and hydrodynamic particle-wall interactions. The former part of the study will concentrate on depletion interactions; the main objective of this work is to achieve controlled and preferential depletion-induced self-assembly of colloids on structured surfaces with specific geometries of interest. In the latter part, we study the effect of depletion interactions on the particle-wall hydrodynamics; specifically, we aim to determine the effect of polymer-induced depletion on the mobility function of hard spheres under confinement. The depletion effect of non-adsorbing dissolved polymers on the interactions between hard colloids and structured surfaces was extensively studied using a set of systematically guided experiments. We will show how the polymer concentration can be used to control the self-assembly of colloidal particles on various surface geometries. We will also present data on the effect of depletion-induced interactions on the hydrodynamic particle-wall interactions under confinement, using particle tracking video microscopy to study the confined dynamics of colloids in a polymer solution. The hydrodynamic coupling between colloidal particles and confining walls hinders the Brownian diffusion of these particles. Our experiments show that the hard sphere hindrance effects are in excellent agreement with analytical predictions from literature across a much wider range of degrees of confinement than previously explored experimentally. It was also found that the hindrance increased substantially in the presence of polymer due to the attractive particle-wall interactions induced by the depletion effects.