Figure 1
From: Effective directional self-gathering of drops on spine of cactus with splayed capillary arrays
(a) Photo of Gymnocalycium baldianum cactus with clusters of 5–6 spines. (b) Optical observation of condensed drop moving on spine (Frame b1-b3). (c-f), ESEM images of the spine. The surface of the spine is covered with scales and the tips of the scales tilt at an angle (α) of ~20°. Cone spine opens an apex-angle δ of ~15° (c). Each scale has a width of ~30–50 μm and a length of ~100–130 μm (d). The tilt-up tips of the scales open a semicircle with a radius (Rc) of ~20 μm (e). The cavities are formed between the scales and the surface of the spine with a radius (rc) of ~8 μm (f). (g) Illustration for the scale-covered spine with an apex-angle δ. The space between the scale and the surface of the spine forms a splayed capillary channel, opening different radius of Rc and rc in two ends. Under the scale, there are parallel grooves.
