Design and optimization of hybrid superhydrophobic-hydrophilic pattern surfaces for improving fog harvesting efficiency

Inspired by the fog harvesting capacity of a wettability gradient pattern on the back of Stenocara beetles, we provide a facile and low-cost method for the fabrication of hybrid superhydrophobic-hydrophilic pattern surfaces, with smooth aluminum alloy substrate as the hydrophilic component and superhydrophobic sticky paper of varying hole sizes as the superhydrophobic component. The fog harvesting efficiency is evaluated by adjusting and combining the hole size of the hybrid superhydrophobic-hydrophilic pattern surfaces. The prepared single aperture hybrid superhydrophobic-hydrophilic pattern surface exhibits an enhanced fog harvesting efficiency compared with the uniform superhydrophobic and hydrophilic surfaces. Furthermore, the fog harvesting efficiency of the prepared combined aperture hybrid superhydrophobic-hydrophilic pattern surface is 88.3 % higher than that of the single set-up. The dynamic fog harvesting mechanism demonstrates that the optimal combined aperture hybrid surface maximizes the number of coalesced droplets within a certain period to collect additional water droplets, thus optimizing the fog harvesting efficiency. The fog harvesting efficiency reaches a maximum of 362.5 mg/cm2/h. The hybrid superhydrophobic-hydrophilic pattern surface prepared in this study has potential applications in atmospheric water collecting.