Droplet actuation by coupling corona discharge and contact electrification: Domino coalescence and uphill braking

Abstract

Directed transport and control of droplets is essential for many modern technologies. Here, we propose an active control mode that combines corona discharge and contact electrification to efficiently drive the droplet or droplet group in a directed manner. In particular, we also implement a continuous coalescence of droplets, similar to dominoes. Moreover, due to the high adhesion effect caused by contact electrification, the droplet can stick on a slope without sliding down, even when the corona discharge is turned off. Interestingly, it can easily slide down when a conductor is nearby. Therefore, a droplet climbing, braking, and downhill system can be realized, and the gravitational potential energy stored by the droplet can be effectively regulated by the applied voltage. This work opens the possibility of droplet manipulation in modern applications such as miniaturized energy storage, biochemical medicine, and self-cleaning.