High efficient fog-water harvesting via spontaneous swallowing mechanism-Yongmei Zheng

Inverse wettability gradient movement triggered by water droplets’ surface energy is conductive to many fields, such as droplet transport, water supply and water nanogenerator. Here, a novel phenomenon of spontaneous inverse wettability gradient movement of droplet (i.e., the “swallowing”) is revealed (with an energy trans-formation ratio at 64.1%) and successfully applied to a new fog-water harvester (i.e., unique gradient wire: UGW). In wetting area on UGW, the largest droplet hanging on more hydrophilic end acts as a gluttonous droplet moving towards inverse wettability to continuously coalesce other droplets and to gain kinetic energy from released surface energy of droplets, resulting in an accelerative reciprocating action like a windshield wiper. As for a given fog flow of 150 g s? 1 m? 2 , the maximum kinetic energy and velocity of the gluttonous droplet are 1.83 μJ and 3.8 cm s? 1 , respectively. This process needs no extra energy consumption and realizes a high water harvest efficiency (1.83 μL cm? 1 s? 1 ). This “Swallowing” action on such UGW allows droplet to accelerate gradually, which is beneficial to power generation from surface energy, heat transfer, and fog-water harvesting, etc.