  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.
