Figure 4

Outside radial movement of droplet on surface of Sample-A at ~150 ^oC.

a) Droplet moves from center to right periphery. b) Droplet moves from center to top periphery. c) Droplet moves from center to left periphery. d) Droplet moves from center to bottom periphery. When the droplet is dripped beside the center of the surface, it slides along the outside radial direction (i.e., wettable gradient direction) and sliding off the surface in less than ~500 ms. Inside radial movement of droplet on surface of Sample-B at ~150^oC. e) Droplet moves from above periphery to center. f) Droplet moves from left periphery to center. g) Droplet moves from right periphery to center. h) Droplet moves from bottom periphery to center. When the droplet is dripped at the periphery of the Sample-B surface, it could slide along the inside radial direction (i.e., wettable gradient direction) and move to the center of graphite plate in less than 600 ms. i) Sliding velocities of droplets on different points on surface of Sample-A at ~150 ^oC. j) Sliding velocities of droplets on different points on surface of Sample-B at ~150 ^oC (r is the distance to center of graphite plate). The volume of the droplet is 10 μL. The scale bar, 10 mm.