Stability and collapse of holes in liquid layers on bounded substrates

We study experimentally and theoretically the stability regime and collapse dynamics of holes in liquid layers on bounded substrates having different wettabilities. It is shown that a critical diameter d_c exists which is a measure indicating the onset of hole closure. d_c depends, among others, on the thickness of the layer, the wettability of the substrate as well as the size of the domain. The wettability of the substrate only has a minor influence on d_c, whereas the influence of the size of the substrate is pronounced. The experimental results are in good agreement with the theoretical predictions of the stability threshold for a broad range of wettabilities and substrate sizes. We further show that the collapse dynamics and the evolution of the minimum thickness of the liquid film after collapse obey different power laws. Surface tension triggers the collapse of the hole, whereas the dynamics of the collapse is solely determined by inertia. By contrast, the evolution of the minimum thickness of the liquid film after collapse is the result of a balance between capillary and inertial forces. Corresponding scaling coefficients are determined.