Evaporation of sessile liquid droplets

The evaporation of sessile liquid droplets on a completely wetted substrate is a complex dynamical process. Available models assume that the evaporation flux is controlled by the stationary diffusion of the liquid molecules in the atmosphere, and that the interface is in equilibrium with the gas phase just above it. This assumption must be reconsidered at the moving contact line, but the description of the thin edge of the drop is still an open question. The present paper reports experiments performed with alkanes on bare and grafted silicon wafers. It is shown that the short range part of the interaction plays no role on the dynamics, but provides an indirect evidence of the presence of a mesoscopic evaporating film left on the substrate ahead of the receding contact line.