Shear-driven depinning phenomena of collodial suspensions in different geometries
Depinning is a nonequilibrium transition well known from systems consisting of collectively interacting particles driven over a substrate, with connections to other topics such as to glassy behavior, jamming and active matter systems. Interestingly, depinning transitions are also observed in dense colloidal suspensions in strong spatial confinement under shear. Understanding the corresponding dynamics is key for applications such as thin film lubrication and surface coatings.
Here, we perform overdamped Brownian dynamic (BD) simulations of strongly confined suspensions of charged colloids under shear in different geometries. In the first case, the colloids are confined to a narrow slit-pore, which induces the formation of a few well-defined layers with crystalline inplane structure. We find that the dynamics of this system is dictated by the frictional dynamics between the crystalline layers, displaying a pronounced depinning transition. In the second case, we consider a planar system consisting of two individually driven rings, confining additional particles between the inner- and the outer ring (Taylor-Couette geometry). For both cases, we identify the dominating transport mechanisms which govern the overall dynamics of the system.