A double-layered coating with patterned wettability for efficient fog collection

Fog collection is a green and environmentally friendly strategy to alleviate water scarcity, which can be well achieved by endowing the microstructural surface with special wettability property. However, it is always limited to the producible small sized surface and low efficiency of fog collection, or hindered by the poor durability. In this study, a double-layered coating with patterned wettability in a large scale is prepared by a facile double-layer spraying method, which integrates collection platform, curved track and storage area. A hydrophilic tree-shaped pattern and its surrounding superhydrophobic area are designed on the collection platform. Both mist and large droplets can be well collected on such a platform without failure of the superhydrophobicity and gravitational assistance, resulting in a superior efficiency of fog collection compared to the exist literatures. A theoretical model is further established to reveal the mechanism that the superhydrophobicity remains effective in a foggy environment. In addition, the curved track embedded in an inclined plane can transfer the collected droplets to the storage area at any position. The preferable durability of the double layered coating can last for several months. Such a design can provide an efficient prototype for freshwater collection in desert and arid regions.