Cacti- And Shorebirds-inspired Transports Of Liquid Drops And Two Related Fog Collectors

Abstract

Motivated by what has been used in cacti and shorebirds to directionally manipulate water drops, we have explored two approaches to guide the movement of liquid drops. Based on these approaches, in addition to separating oil from its mixture with water, we have further developed two fog collectors. The first fog collector has a configuration similar to its counterpart in a cactus. This collector includes a large ZnO wire and an array of small ZnO wires that are branched on the large wire. All these wires have conical shapes, whose diameters gradually increase from the tip to the root of a wire. This diameter gradient induces a capillary force to transport condensed drops from the tips to the roots of the wires. This single branched wire structure collected about 6 µL water within 30 min.As in the case of a shorebird, the second collector employs two nonparallel plates to direct the movement of condensed drops. The two nonparallel plates are first widely opened to provide a large surface area for water vapors to condense. The condensed drops are then transported to the corner of the two plates for collection, after these drops are squeezed and relaxed using the plates. A single 10-inch by 4-inch prototype "swallowed" about a tablespoon of water in 36 minutes. Over two hours, it harvested 400-900 times more water than beetles and cacti in desert areas.