Efficient fabrication of desert beetle-inspired micro/nano-structures on polypropylene/graphene surface with hybrid wettability, chemical tolerance, and passive anti-icing for quantitative fog harvesting

Obtaining fresh water from the atmosphere by fog collectors is a promising way to meet the challenge of the water crisis. Bioinspired fog collectors have attracted widespread attention, but their application is limited by complex preparation processes and weak environmental adaptability. Herein, an efficient method that combines extrusion compression molding and surface modification is proposed for the large-scale fabrication of united superhydrophobic-hydrophilic polypropylene/graphene nanosheets (UPP/GNS) films for quantitative fog harvesting. Specifically, the desert beetle-inspired micro-pillars on the UPP/GNS surface exhibit a hydrophilic top and a superhydrophobic bottom and sidewall. A micro-nano/structure-induced hybrid wettability is acquired with a CA of 160 ± 3°. The hybrid wettability is excellent in accelerating droplet condensation and aggregation, which is beneficial for mass transfer in a fog harvesting system. Importantly, excellent chemical tolerance, passive anti-icing, active photothermal anti-icing, and sufficient durability enable the UPP/GNS film to maintain a stabilized fog collection efficiency under various external disturbances, such as salt, acid-/alkali solutions, and high temperature. Finally, the combination of hydrophilic and superhydrophobic wettability endows the UPP/GNS film with a fog collection efficiency of 1251 mg cm-2h−1. The economical and mass production method for the efficient fabrication of high-efficiency UPP/GNS fog collectors is a promising solution for mitigating the global water shortage.