Hydrophilic slippery surface enabled coarsening effect for rapid water harvesting

Abstract

Water harvesting through the condensation of vapor in air has the potential to alleviate water scarcity in arid regions around the globe. When water vapor is condensed on a cooled surface, tiny water droplets act as thermal barriers. Thus, they must be removed rapidly for efficient water harvesting. Passive technologies for droplet removal rely on in-site growth and direct contact of densely distributed droplets. However, it is challenging to remove submicrometer droplets that lead to a poor water harvesting rate. Here, we present a coarsening effect to rapidly remove water droplets with diameters <20 μm from the hydrophilic slippery liquid-infused porous surface (SLIPS). We quantitatively study the driving and drag forces to enhance the rapid droplet size evolution. The self-propelled coarsening effect enables rapid droplet removal regardless of surface orientations, showing a promising approach compared to those on PEGylated hydrophilic surface, hydrophobic SLIPS, and superhydrophobic surface in water harvesting.