Drops that pull themselves up

We relate different existing literature experimental findings of drop retraction in evaporating or in coffee ring systems as a unique physical phenomenon that is not related to evaporation, but rather to the presence of surfactant molecules in the drops. The retraction is induced by fluctuations of the dropʹs triple line that result in a net leakage of the surfactant molecules onto the solid-air interface right across the triple line. This net leakage can be induced by either nucleation and growth of a surface defect at the triple line or random triple line fluctuations analogous to spinodal process. Using this understanding, we can set a lower limit to the value of the, otherwise un-measurable, solid-vapor interfacial energy.