Intrinsic analysis of dynamic wetting on soft surfaces

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Surface phenomena are remarkable because they are dominated by extreme forces localised right at the interfaces, in a spatial domain that usually involves few (1-3) molecular layers. In case of fluids or soft materials, however, thermally activated surface capillary waves corrugate the interface on larger scales, frustrating the attempt to investigate its structure and dynamics at molecular resolution through conventional analyses of atomistic simulation trajectories.Intrinsic analysis approaches, instead, by undoing the smearing effect of capillary waves have been used with success in recent years to analyse the structure of liquid/vapour and liquid/liquid interfaces. In this project, we propose to generalise these approaches to ternary systems and apply them to liquid droplets on soft substrates, to obtain a clearer picture of the molecular structure and dynamics close to the contact line at thermodynamic equilibrium, and, during the process of depinning. In our proposed approach, we will study both a simplified model of droplet/soft substrate, and, a realistic model at atomistic resolution of a water droplet on the surface of a polyelectrolyte multilayer. The model system will enable us to span a wide range of parameters, including different type of solutes, and, therefore, to investigate trends and to compare with, and extend, available theoretical models. The water/polyelectrolyte system, on the other hand, will give us the opportunity to investigate the link between the microscopic changes at the contact line and the macroscopic effects in a quantitative way, and to compare them directly with experimental measurements. With this approach, we will bring the current picture of the properties of the moving contact line to an unprecedented resolution.