Dynamics of a drop at a liquid/solid interface in simple shear fields: A mesoscopic simulation study

The dynamics of a surface-confined drop in a simple shear field has been studied, pursuing the dissipative particle dynamics (DPD) simulation approach. The shear field induces contact angle hysteresis in the drop, the degree of hysteresis increasing with the shear rate. At shear rates exceeding a critical value, the drop acquires the tendency to lift off the boundary, leading to its removal. In the equilibrium contact angle range, ϑe>120°, the drop preserves its integrity as it escapes from the boundary, whereas at lower contact angles the drop assumes a distinctly elongated shape prior to its removal, which develops “necks’' at subsequent times. The drop breaks up as the necks are ruptured upon thinning, with some fragments escaping into the bulk phase and some remaining at the surface. Under certain hydrodynamic conditions the moving drop sheds a trail of tiny droplets on the surface. The simulation results are in qualitative agreement with experimental studies on the corresponding systems published in the literature.