Instability of Confined Water Films between Elastic Surfaces

Abstract

We investigated the dynamics of nanometer thin water films at controlled ambient humidity adsorbed onto two atomically smooth mica sheets upon rapidly bringing the surfaces into contact. Using a surface forces apparatus (SFA) in imaging mode, we found that the water films break up into a distribution of drops with a typical thickness of a few nanometers and a characteristic lateral size and spacing of several micrometers. Whereas the characteristic length is found to be independent of the ambient humidity, the characteristic time of the breakup decreases from approximately 1 to 0.01 s with increasing humidity. The existence of characteristic length and time scales shows that this breakup is controlled by an instability rather than a conventional nucleation and growth mechanism for SFA experiments. These findings cannot be explained by a dispersion-driven instability mechanism. In contrast, a model involving the elastic energies for the deformation of both the mica sheets and the underlying glue layer correctly reproduces the scaling of the characteristic length and time with humidity.

Liquid dewetting under a thin elastic film

“…Few studies have investigated the intersection of dewetting and elastocapillarity; those that do have focused on a liquid dewetting off a bulk elastic solid and have chiefly been theoretical in nature [31][32][33][34][35]. Some studies have investigated systems where the liquid film is capped by a thin, compliant elastic layer [36][37][38][39]. In one set of experiments, the dewetting of thin water films between two sheets of mica, several microns thick, was observed [36,38].…”

OpenHumidistat: Humidity-controlled experiments for everyone

“…Systems designed to adjust the humidity in experiments are often based on equilibria of water vapour with salt solutions [2,3], local heating of a water bath in a reservoir chamber [4,5], or using an air stream composed of a mixture of approximately dry and water-saturated air [6,7,8,9] that is manually mixed in varying ratios. The first method provides stable control, but is very inflexible: for every value of humidity, a specific salt is required.…”

Design, construction, and testing of an accurate low-cost humidistat for laboratory-scale applications

“…The disadvantage is that this diffusion tends to be slow as well. A faster alternative is to use an air stream consisting of a mixture of dry and water-saturated air guided towards the sample [1,[8][9][10]. However, the lack of closed-loop control combined with its susceptibility to external disturbances and long response times renders this set-up very arduous to control manually.…”