Figure 1.

Composite wetting: Drops are suspended on top of the roughness features, with air trapped underneath. The drops are resting on a carpet composed of solid and air; the term “composite” is therefore used. (a) Schematic depiction and (b) micrograph of a drop on a microscale post surface. The width of the posts was 16 μm. (c) The surface from b has been rotated by 90°. Even though the drop was in the composite state, the hysteresis was considerable, as witnessed by the fact that the drop stuck to the surface even at extreme tilting angles.