Atmospheric Water Harvesting on Micro-nanotextured Biphilic Surfaces

Water scarcity is an acute worldwide problem with increasing frequency even in the developed countries of Europe. Nature has inspired scientists to carry out atmospheric water harvesting both from fog and dew on surfaces of extreme wettability or biphilic surfaces (surfaces with hydrophilic and hydrophobic patterns). Literature reports exhibit large variation and contradictory results. Herein, we systematically study the effect of the different biphilic shapes on both dew and fog harvesting, clarifying the variable results observed in the literature. First, we demonstrate a facile and scalable method of biphilic surface fabrication using plasma micro-nanotexturing, plasma deposition, and plasma etching through a stencil mask. We comparatively study the water collection performance of three different biphilic pattern shapes and two uniform patterns, in two different harvesting modes, namely, dew harvesting and fog collection. Our results demonstrate superior atmospheric water collection efficiency for biphilic patterns. We demonstrate increased rate compared to untreated surfaces, 2× for fog collection, and 1.6× for dew harvesting. We also demonstrate that biphilic spot- and biphilic path-like patterns behave differently depending on the harvesting mode: spot patterns show maximum water collection in fog collection and minimum in dew harvesting, whereas path-like patterns show maximum water collection in dew harvesting.