New Insights Into The Prediction Of Adaptive Wetting Of A Solid Surface Under A Liquid Medium

The wetting of a solid surface by a liquid droplet under a liquid medium not only includes the solid-droplet molecular interactions but also involves the interfacial interaction with the surrounding medium. Such wettability adaptation evolves either due to the formation of a thin film of the surrounding medium over the solid surface, or the molecular reorganization at the solid-liquid interfacial region. Here we developed a theoretical framework and proposed a novel experimental approach to evaluate the solid-medium interfacial tension by implicitly involving the adaptation behavior of a solid surface in the presence of another liquid. We investigated the wettability of three solid surfaces, namely glass, poly(methyl methacrylate) (PMMA), and polytetrafluoroethylene (PTFE), for a wide range of polar and non-polar oil droplets underwater. From our proposed two-liquid approach, we measured the polar and non-polar solid surface tension components. Our experimental results revealed the significant impact of interfacial tension of both droplet and the surrounding medium on the overall wettability of the solid-medium-droplet system. The predicted results were within +/- 25% deviation from that of the experimental observation for most of the cases. In contrast, the application of the previously reported theories resulted in a larger deviation (above +/- 35%) for all samples.