Bioinspired silica-based sol–gel micropatterns on aluminium for humid air condensation

Several patterned coatings with a hybrid organic-inorganic nature were deposited on metallic substrates by exploiting the dewetting of a sol–gel bilayer. The hybrid coatings, inspired by the exoskeleton of a desert beetle, consisted of hydrophilic silica droplets on a hydrophobic CH3-silica bottom layer. The patterned morphology was tuned by changing the initial solution concentration, which resulted in substantial changes in the size and the density of distribution of the hydrophilic droplets. The reproducibility of the dewetting process on metallic substrates was confirmed, together with its scalability over large area substrates. The real-life application of the patterned coating for atmospheric water harvesting was tested in a custom-made apparatus, which demonstrated that the patterned coating led to a higher collected mass during condensation from humid air compared to the bare aluminium substrate. The patterned coating was proven to maintain its structure after the humid air exposure, confirming the robustness of the sol–gel-based materials.