Reversible switching between isotropic and anisotropic wetting by one-direction curvature tuning on flexible superhydrophobic surfaces

In this letter, we report a kind of smart surfaces with reversible switching between isotropy and anisotropic wetting, which was realized by one-direction curvature tuning on flexible superhydrophobic surfaces. Along the curvature change, the wettability of this flexible film was changed from isotropic state (150°/150°) into anisotropic state confirmed by its anisotropic contact angles (150°/160°) and sliding properties (30°/65°). Further investigation revealed that the surface wettability was changed from composited pinned state into transitional state. This was attributed to the increase in roughness factor and the decrease in the contact area between the water droplet and the pillar array. At last, we demonstrate that the wetting states between isotropy and anisotropy on this flexible superhydrophobic film could be reversibly switched by curvature for many times (>10).