Numerical and Experimental Investigation of Static Wetting Morphologies of Aqueous Drops on Lubricated Slippery Surfaces Using a Quasi-Static Approach

TL;DR

This study combines numerical simulations and experiments to analyze the static wetting morphologies of aqueous drops on lubricated surfaces, revealing good agreement and insights into how parameters affect contact angles.

Contribution

It introduces a quasi-static computational approach for predicting wetting morphologies using interfacial energies and validates it with experimental data.

Findings

Good agreement between simulations and experiments for interface profiles and contact angles.

Contact angles depend non-linearly on substrate wettability and lubricant thickness.

Drop volume has negligible effect on apparent contact angles.

Abstract

Due to the slow dynamics of the wetting ridge, it is challenging to predict the wetting morphology of liquid drops on thin lubricant coated surfaces. It is hypothesized that when a drop sinks on a lubricated surface, quasi-static wetting morphology can be numerically computed only from the knowledge of interfacial energies, lubricant thickness, and drop volume. We used Surface Evolver software for the numerical computation of the interface profiles for a four-phase system. For the experiments, we used drops of 80 wt% formamide on silicone oil coated substrates with varying lubricant thickness, substrate wettability and drop volume. Optical images of drops were used to compare the experimental interfacial profiles and apparent contact angles with the numerically computed ones. We found good agreement between the experiments and the simulations for the interfacial profiles and apparent contact angles as a function of various systems parameters except for very thin lubricating films. Apparent contact angles varied non-linearly as a function of substrate wettability and lubricant thickness, however, were found constant with the drop volume.