Dynamics of dewetting

The dynamics of dewetting is re-examined from a theoretical perspective and in the light of experiment. Two cases are considered: (a) spontaneous dewetting following rupture of a thin liquid film previously formed on a partially wetted solid surface; (b) steady dewetting when a partially wetted solid surface is withdrawn vertically from a pool of liquid. In the first, a rim of liquid forms at a circular dewetting front that expands at constant speed, while the remainder of the film remains quiescent. The second is characterised by the formation of a serrated contact line, in which each straight-line section also recedes at a constant normal velocity, but with no significant rim. These two cases are analysed in terms of the relevant dissipation processes. Hydrodynamic dissipation is estimated using a simple model proposed by de Gennes, while the molecular-kinetic theory accounts for contact-line friction. The new analysis suggests that for a given system, the dewetting velocities and dynamic contact angles seen in the two cases are likely to be different. In (a), they will be the outcome of both dissipation channels operating in parallel, whereas in (b), both parameters will be determined by a dynamic balance between the two sources of dissipation that avoids an inflection in the liquid–vapour interface near the receding contact line. These predictions are consistent with current observations and could be tested by well-designed experiments.