Dual-scale micro/nanostructures for high-efficiency water collection

We describe a simple method of synthesizing dual-scale dome-like micro/nanostructures on copper using temperature controlled surface oxidation. The produced surfaces show two conflicting attributes, large contact angles and large droplet departure radii. Together, these two attributes promote water collection from air. A range of 80%-100% collection rate enhancements was observed for copper surfaces with a number of different wettability characteristics. Theoretical results showed that large departure droplets introduce strong disturbances in the diffusion boundary layer, which may be responsible for decreasing the vapor mass transfer resistance and enhancing the rate of water collection through moisture condensation. (C) 2017 Elsevier Ltd. All rights reserved.