The effect of miscibility on the nanoscale dynamics of wetting

Wetting and dewetting dynamics span multiple scales, with nanoscale viscous bending of interfaces and liquid-solid friction impacting rheology up to the macroscale. Our study examines how miscibility influences friction at the three-phase contact line (contact line friction). Large-scale molecular dynamics simulations are employed to explore wetting regimes and molecular interfacial effects, which would be extremely challenging to inspect experimentally. We focus on silica-like surfaces to capture hydrophilic interactions with polar liquids like water. The first simulation set we present examines the spreading dynamics of aqueous glycerol droplets. Glycerol concentration is varied to mimic viscosity adjustment in experiments. Existing theoretical and semi-empirical correlations fail to predict the observed scaling between viscosity and contact line friction. Our results are explained by extending Molecular Kinetic Theory to liquid mixtures and considering interfacial effects such as adsorption and depletion. In the second set, confined water-butanol meniscus are examined. Partial miscibility leads to a low-tension diffuse interface between the two liquid phases. We aim to quantify the impact of mixing at the interface on solid friction and compare molecular simulations with Cahn-Hilliard Navier-Stokes equations.