Liquid Collection on Superomniphilic Wavy Surfaces

There is great need for functional surfaces to promote efficient liquid collection from droplet-laden air flows, with applications including water harvesting, building climate control, thermal power generation, and desalination. Current state-of-the-art flat surfaces utilize hydrophobicity to promote high droplet mobility for improved drainage, but the surfaces lose their hydrophobicity at high supersaturation conditions. In this work, we design a self-regulating omniphilic surface for much improved liquid collection rates, with inspiration from the remarkable fog and dew collection ability of the Welwitschia mirabilis, a plant which can survive for thousands of years in the Namib Desert. The surface is designed with a periodic wavy structure, with millimeter-scale features tuned such that liquid deposition is focused on the peaks and the pressure-driven flow from peak to valley is dominated by capillary forces rather than gravity. The filmwise transport is then critical for the instantaneous wicking of liquid into the valley region where it is sheltered from the bulk flow, thus minimizing re-entrainment and evaporation. As such, this is a self-regulating and highly durable surface for efficient long-term liquid collection, with many energy and sustainability applications.