Multistep Wettability Gradient on Bioinspired Conical Surfaces for Water Collection from Fog

Water scarcity is on the rise globally. In severely arid deserts, nature has developed different mechanisms to transport water collected from fog and condensation before it is evaporated. This water is either stored or consumed. Some of the studied mechanisms are Laplace pressure gradient, grooves, and gravity. Another way to transport water is through heterogeneity in wettability, in which a droplet moves from a water repelling (hydrophobic) region to a water loving (hydrophilic) region. A combination of multistep heterogeneity on a bioinspired conical surface is studied to provide fast movement of water droplets. A representative cone was selected, and its water collection rates at different wettabilities were measured.