Optimized Fog-Harvesting Material to Provide Drinking Water for Dry Regions

Systems that harvest the tiny airborne droplets of fog and turn them into potable water exist in at least 17 nations. Now researchers at MIT, in collaboration with colleagues in Chile, have found that their efficiency in a mild fog condition can be improved by at least fivefold. Fog-harvesting systems generally consist of a vertical mesh. The researchers have found three key parameters to efficient harvesting: the size of the filaments in those nets, the size of the holes between those filaments, and the coating applied to the filaments. The best performance comes from a mesh made of stainless-steel filaments about three or four times the thickness of a human hair, and with a spacing of about twice that between fibers. The mesh is dip-coated, using a solution that decreases a characteristic called contact-angle hysteresis. This allows small droplets to more easily slide down into the collecting gutter as soon as they form.