A radial wettable gradient was fabricated on the surface of graphite plate by a simple one-step
anodic oxidation process. It was found that the direction and value of the wettable gradient could
be easily controlled by adjusting current and oxidation time gradient. With the increase of surface
temperature, droplets on surface not only exhibited the transition of boiling mode, but also showed
the controlled radial spreading, evaporation and movement behaviors. These phenomena could be
attributed to the cooperation of wettability force, hysteresis force and vapor pressure (Leidenfrost
effect). Especially, the controlled radial convergence or divergence of droplets with high velocity
were realized on the surfaces with either inside or outside radial gradient, which would have crucial
applications in the design of microfluidic devices and the exploration of the biotechnology
