Titanium dioxide (TiO 2 ) is an important material that is used in many industrial applications related to photo-splitting of water, [1] photocatalysis, [2] photovoltaic devices, [3] etc. Since the discovery [4] of photoinduced superhydrophilicity (water contact angle (CA) < 108) on a hydrophilic TiO 2 surface in 1997, many research efforts [5][6][7][8] have been devoted to exploring this photosensitive mechanism with the aim of manipulating the surface wettability to a larger extent in virtue of the good light, thermal, and chemical stability and better biocompatibility of TiO 2 than of other organic or inorganic materials. However, its wettability has only been tuned in a limited region thus far.
In the past several years, inspired by the surface-topography-induced superhydrophobicity of lotus leaves [9,10] and water striders legs, [11] various films that exhibit superhydrophobic properties have been fabricated. [12][13][14][15][16][17][18][19] On the other hand, superhydrophilic surfaces have been realized by taking advantage of a 2D [4] or 3D [20] capillary effect. Very recently, several stimuli-responsive, smart, interfacial materials that can be switched between superhydrophilicity and superhydrophobicity by combining the geometrical morphology of [*] Dr.