Motion behaviour of water-droplet on alternate superhydrophobic/hydrophilic ZnO wetting-patterned surface

The wetting-patterned surfaces with alternate superhydrophobicity and hydrophilicity were designed and prepared by a facile solution growth of ZnO nanorods on selectively masked ZnO nanocrystals. The as-prepared patterned film was characterized by SEM; its wetting behaviour was evaluated using a contact angle measuring device. The ZnO-patterned film is composed of hydrophilic ZnO nanograins with a water contact angle of similar to 32 degrees and superhydrophobic ZnO nanorod arrays with a contact angle of similar to 154 degrees. From the observation of motion behaviour of water-droplets on the patterned films, the static water-droplet on the interface between superhydrophobic and hydrophilic regions moves towards the hydrophilic region in a self-driving way. The motioning water-droplets bypass the superhydrophobic region and then move to the hydrophilic region, even though the latter has a stronger adhesion resistance than the former. Such self-driving and bypassing behaviour can be attributed to their different surface tensions on the superhydrophobic/hydrophilic interface.