Figure 3. Water drop transport on BFGS with weak/strong gradient spindle-knots.

(a), In weak gradient spindle-knots, water drops (1,2,3,4,5) hanging on single spindle-knots and joint, and form a big drop (1 + 2 + 3 + 4 + 5) via transferring from smaller spindle-knot to bigger ones at ~1.36 s. The transport length (L_a) is ~1.41 mm (see distance between both vertical dash lines) with time of ~1.36 s. (b), In strong gradient spindle-knot, water drops move directionally and hang between two spindle-knots. The length (L_b1) of movement to bigger spindle-knot is ~2.70 mm. The drop is coalesced with small drops (1,2,3,4) at ~2.08 s and the last drop (1 + 2 + 3 + 4 + 5) moves to right point location of two biggest spindle-knots (at ~2.12 s). The transport length (L_b2) is ~3.76 mm (see distance between both vertical dash lines) with time of ~2.12 s. Scale bars, 500 μm.