Dynamics of hard and soft colloids in confined geometries and on structured surfaces

Abstract

We investigated the depletion interactions of colloids and hindrance behavior of hard and soft colloidal particles near neighboring walls. We first used numerical modeling to compute depletion interaction strengths for simple geometries which eventually guided our experiments to make interactions highly selective. The model helped us in identifying the important parameters to finetune these interactions and shed light on geometric design rules to optimize desirable shape-selective interactions on a variety of complex geometries. We further reported experimental studies that highlight the differences in the dynamics of hard and soft colloids under confinement using video microscopy and particle tracking. It was found that both soft sphere systems that we investigated (swollen polymer particles, core/shell microgels) behave differently from hard sphere systems under all degrees of confinement that were measured. Our findings suggest that soft sphere systems have lesser hindrance compared to hard sphere counterparts and the hindrance varies as a function of softness. In order to understand the soft sphere confinement dynamics more clearly, implications for future research are discussed.