Charge Density Gradient Propelled Ultrafast Sweeping Removal of Dropwise Condensates.

Continuous sweeping of dropwise condensates is an effective form of vapor to liquid transition in terms of thermal transport at a solid/liquid interface. However, using conventional approaches, it is difficult to simultaneously achieve small activating size and fast departure of condensed droplets with high efficiency, due to the insufficient driving force compared to adhesion. Here, we propose an unexplored method to stimulate a frequent sweeping removal of dropwise condensates at ultrahigh efficiency on a superhydrophobic substrate, aided by a charge density gradient (CDG). We show that the CDG can be injected inside a superhydrophobic substrate on which the condensate droplet with jump-induced charges starts to sweep at a small size down to the microscale followed by quick snowball-like growing and chase-like propelling. The incorporation of the CDG on a superhydrophobic substrate enables a continuous, fast, frequent, long-range, and gravity-independent droplet removal during condensation, making this strategy a promising solution for diverse applications in water harvesting, antifogging, and anti-icing.