Harps Enable Water Harvesting under Light Fog Conditions

Abstract Fog harvesting is useful for passively collecting fresh water in arid regions, but the efficiency of current mesh‐based harvesters is compromised by their poor drainage. Inspired by the linear needles of redwood trees, “fog harps” are developed whose array of vertical wires enables an unobstructed drainage pathway. A full‐scale (1 m² frame) fog harp is fabricated by winding a stainless steel wire around a spinning aluminum frame featuring threaded rods. The fog harp is field tested for a full year at a local farm (Blacksburg, VA, USA), alongside the control case of a mesh harvester. Under moderate fog conditions, the fog harp collects anywhere from 2 to 78 times more water compared to the mesh harvesters. Under light fog conditions, the fog harp collects up to several hundred milliliters of water per day while the mesh is unable to collect any water at all. The water harvesting performance of fog harps is therefore unprecedented in two ways: they substantively elevate the performance ceiling when exposed to healthy fog while also enabling, for the first time, appreciable water harvesting under light fog.