Self-propelled Droplet Movement on Micro/nano Anisotropic Structures Surface

The micro/nano anisotropic structures was controllably fabricated by soft lithography using polydimethylsiloxane(PDMS) and Co nanoparticle composite under the external magnetic field and covering of ZnO nanohairs via nanocrystalline growth technique. The sample is covered with periodicities of ca. 400 μm conical fibers and the conical fibers diameter of ca. 200 μm. The tip diameter of cone is ca. 80 μm. The length of the cone is ca. 1 mm. The ZnO nanohairs cover fully over every fibers, where the ZnO nanohairs have the diameters of 80-100 nm and the lengths of ca. 1 μm. The sample is hydrophobic with a contact angle of 142.5° andanisotropic wettability. The result indicates that the droplets can roll under vertical vibration or bounce directionally. This finding offers an insight into design of functional structures for droplets move in direction.