Water collection and transportation on superhydrophilic/superhydrophobic bioinspired heterogeneous wettability surface

In recent years, the ability of superhydrophilic/superhydrophobic bioinspired heterogeneous wettability (SSBHW) surfaces to collect freshwater has gained significant attention due to their potential to mitigate water scarcity. Inspired by nature's creatures, this paper presents an SSBHW surface that can efficiently collect freshwater resources from the atmosphere, drawing inspiration from cactus needles and spider silk spindles. The superhydrophobic (SHO) surface was prepared by wet etching and low surface energy modification on copper surface. Based on the SHO surface, the superhydrophilic (SHI) patterns consisting of spindle-shaped and wedge-shaped were constructed by laser ablation. The prepared SHI pattern was not only trapped airborne droplets but also enabled the directional transport of droplets. To enhance the efficiency of water collection, the smaller spindle-shaped pattern spacing in the SHO region was designed, which help to transport the condensed water quickly towards the SHI region because of the surface energy gradient force. The synergistic effect between the advantages offered by the SHO and SHI surfaces results in a significant improvement in water collection efficiency. The water collection efficiency of the SSBHW surface is 870 mg cm−2 h−1, which is 3.32 and 2.2 times higher than that of the SHI and SHO surfaces, respectively. In addition, the mechanism of enhancement of the moisture harvesting behavior of inhomogeneous wettable surfaces was analyzed. This work provides a new strategy for the study of catchment surfaces, making it an effective solution for obtaining fresh water resources in arid regions.