Bioinspired Design of Superwetting Pattern Surface with Bumpy Structure and Radiation Cooling Layer for High Efficient Water-Harvesting Systems

The atmosphere acts as a reservoir that accommodates an appreciable volume of freshwater, which can serve as a valuable resource. The Namib Desert Beetle, found in an extremely arid region, exhibits nonwaxy hydrophilic bumps and waxy hydrophobic depressions, which are effective in harvesting water from air. In this study, superwetting surfaces featuring a "bumpy" morphology have been established, and the associated water harvesting capability has been investigated. The results have established the formation of a hydrophilic-superhydrophobic hybrid surface with bumpy structures produced by an etching procedure (conducted over 20 h), which delivered a water uptake of 4619.0 mg·cm^-2·h^-1. In order to counteract surface evaporation, a radiant cooling layer (RCL) was added to inhibit re-evaporation. Use of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)), with a negligible extinction coefficient across the UV-visible-near-infrared spectral range, minimized light absorption and enhanced reflectivity, contributing to effective radiative cooling. The combination of P(VDF-HFP) and CaF₂ to generate functional particles with a porous RCL increased the water collection efficiency to 4916.6 mg·cm^-2·h^-1. The proposed double-sided functional structure involves a facile preparation procedure, high mechanical and chemical stability, low cost and environmental impact, and high efficiency of water collection, offering an effective means of achieving enhanced water harvesting.