Substrate curvature dependence of intrinsic contact angles

Abstract

The intrinsic contact angle is an essential wetting parameter between a liquid and a substrate and had long been regarded as an intrinsic interfacial property. Recent investigations showed that the intrinsic contact angles depend on substrate curvatures. However, the reported trends were contradictory, and the underlying physics has not been revealed. This paper presents a molecular perspective to understand the intrinsic nature of the curvature effect on the contact angles. Molecular dynamics simulations quantitatively validate the theoretical model without fitting. This general molecular interaction model provides a unified curvature effect on different fluids that the contact angle decreases on a concave substrate and increases on a convex substrate. This curvature effect is amplified on a more wettable substrate and enlarged by a longer-range molecular interaction. We anticipate that the new understanding of nanoscale wetting will give new insights into the design of nano-flow systems and stable superhydrophobic surfaces.