Enhancing atmospheric water harvesting on hydrophilic-superhydrophobic hybrid surfaces through wettability gradient and synergistic diversion channel

Abstract

Climate change and resource depletion have exacerbated freshwater shortages, underscoring the urgent need for sustainable water resources. Atmospheric water harvesting technology, inspired by natural structures-especially fog collection on hydrophilic-superhydrophobic hybrid surfaces-offers a feasible solution due to its simple fabrication process, high collection efficiency, and zero energy consumption. While hydrophilic-superhydrophobic hybrid surfaces show potential for improving water collection efficiency, research on the mechanisms of droplet nucleation, growth, detachment, and transport remains limited. In this study, a hydrophilic porous hybrid surface with tunable wettability was fabricated by adjusting laser processing parameters, achieving a maximum collection efficiency of 1874.7 mg/cm²/h at a contact angle of 6°. The surface energy difference caused by the wettability gradient on this superhydrophilic-superhydrophobic hybrid surface accelerated droplet detachment and transport. Additionally, the introduction of single-row and multi-row diversion channels disrupted the droplet's force equilibrium and enhanced its directional sliding, further increasing the collection efficiency to 3623.1 mg/cm²/h and 4016.9 mg/cm²/h, respectively. Simulation results indicate that the combined effects of wettability-driven forces and Laplace pressure significantly improve the efficiency of droplet nucleation, growth, detachment, and sliding. The tunable wettability hybrid surface developed in this study is highly versatile and can be applied to a wide range of substrates, showcasing substantial potential for atmospheric water harvesting offering a sustainable water resource solution for arid regions.