Figure 8: Demonstration of the anisotropic droplet shape on different types of surfaces.

(a) The difference in the advancing contact angles along the y and x directions for a rectangular droplet were as high as 26° (top), which continued to increase further (bottom) as the droplet was pinned and the contact angle decreased during evaporation to ambient. This level of asymmetry in a liquid droplet is only possible due to the high energy barriers associated with the localized pinning of the contact line along the pillar edges. The strategy was further tested on other geometries: (b) cuboidal pillars and (c) chemically patterned and optically smooth surfaces (D=3 μm and L=8 μm). Scale bar, 20 μm.