Fig. 3. Three modes of oil droplet motion on different patterns.

(A) Regime diagram showing three types of oil droplet behaviors depending on pattern parameters. In the green regime, oil droplets move spontaneously toward the center. In the blue regime, oil droplets remain pinned after being released. In the red regime, oil droplets exhibit outward spreading. The test liquid is hexadecane and the droplet volume is fixed at 1 μl. (B) Time-lapse images illustrating the three modes of oil droplet motion.