Water harvesting by hierarchical surface

Abstract

Atmospheric water harvesting (AWH) is a possible solution of the water scarcity, while superhydrophobic surface is a strong candidate in AWH because of the novel feature of coalescence-induced jumping. Superhydrophobic surface prepared by the route of alkaline oxidation has best opportunity in scalable application because of the benefit of low-cost and simplicity. The fabrication conventionally produces the nano-roughness and micro-flower. Whereas most of the report focus on optimizing the geometric parameter of the nano-roughness and designing the hierarchical structure, which is introducing additional micro-structure prior to the alkaline oxidation. In the meantime, the influence of micro-flower had been neglecting by many reports. Moreover, there has yet to have an agreement to whether micro-flower imposes positive or negative effect to water condensation. To fill the knowledge gap, we had prepared the samples with different local features, including micro-flower, nano-roughness, and micro-structure, to examine their effect to the AWH performance. Furthermore, we had adopted the artificial intelligence (AI) technology to facilitate the quantitative analysis in this work. We found that micro-flower has an essential influence on water harvesting. The micro-flower act as the preferable nucleation site and the promoter to the mobility of the condense droplet. The synergistic effect enhances the frequency of condensation cycleso that the AWH performance is enhanced, where the highest heat flux is 27% higher than the previous work. The linear relationship between the departure volume and the amount of micro-flower confirms the prominent influence of micro-flower in related the other local features.