Figure 3.

Hydrodynamic features of the trichome cluster and conical-shaped pathway. (A) In situ optical microscopic images showing evaporation and absorption of water droplet ~0.5 μL in volume dropped on the trichome cluster. (i) A water droplet is deposited on trichomes in Cassie state due to its wettability. (ii–vii) With continuous water evaporation, the contact line of the water droplet begins to move downward until the droplet transforms into Wenzel state. (viii–x) Finally, the water droplet is rapidly absorbed into the mucilage in a few seconds. (B) In vivo optical microscopic images of a sliced cactus stem. A conical-shaped pathway exists under the trichome cluster (left). Magnified image of its sharp end (right). (C) (i) SEM image of the conical-shaped pathway in lyophilized trichome cluster. (ii) The pathway starts from the trichome cluster marked by blue arrow. Scale bars, 300 μm (A) and 30 μm (B).