Precise tuning of surface wettability - by means of curvature-driven reversible switching from the pinned to the roll-down superhydrophobic state (see figure) - is reported for the first time. The adhesion force and sliding behaviors of superhydrophobic poly(dimethylsiloxane) (PDMS) pillar arrays show a strong dependence on surface curvature. Alteration of the curvature of the surface allows a water droplet to be easily adjusted from the "pinned" to the "roll-down" state, which provides the possibility of precise, in situ control of the movements of water droplets.