Figure 5.

Principle of ‘interconnection’ for two saw-tooth-shaped capillary channels. (a) An applied droplet is soaked into the structure by capillary forces. The liquid front stops at the sharp edges in capillary I, while it is transported farther into capillary II. As the liquid front in capillary II reaches the nearby interconnection the liquid is transported into capillary I. (b) The liquid coming through the interconnection picks up the stopped liquid in capillary I and forms a new free liquid front. Thereafter, the liquid is transported through a second interconnection into capillary II, where the stopped liquid is picked up. (c) Advancing water droplet on a biomimetic prototype laser engraved into PMMA. Characters indicate the same situations as in (b). (Online version in colour.)