Geometry-dominated fluid adsorption on sculpted solid substrates

The shape(1,2) and chemical composition(3) of solid surfaces can be control led at a mesoscopic scale. Exposing such structured substrates to a gas tha t is close to coexistence with its liquid phase can produce quite distinct adsorption characteristics compared to those of planar systems(4), which ma y be important for technologies such as super-repellent surfaces(5,6) or mi cro-fluidics(7,8). Recent studies have concentrated on the adsorption of li quids on rough(9-11) and heterogeneous(12) substrates, and the characteriza tion of nanoscopic liquid films(13). But the fundamental effect of geometry on the adsorption of a fluid from the gas phase has hardly been addressed. Here we present a simple theoretical model which shows that varying the sh ape of the substrate can exert a profound influence on the adsorption isoth erms of liquids. The model smoothly connects wetting and capillary condensa tion through a number of examples of fluid interfacial phenomena, and opens the possibility of tailoring the adsorption properties of solid substrates by sculpting their surface shape.