Dynamic surface potential gradient for charged droplet manipulation

Abstract

Droplet manipulation with specific functionalities expands its practical applications. This study combines droplet motion and reactivity through a dynamic surface potential gradient. A conductor is positioned to approach and partially overlaps the charged path on a superamphiphobic surface from the underside. In the overlapping area, the net charge density decreases, creating a static surface potential gradient around the boundary. Movement of the conductor induces a dynamic surface potential gradient along the printed charge path. Droplet manipulation is achieved through the asymmetric electrostatic forces provided by the dynamic surface potential gradient. The magnitude of the dynamic surface potential gradient can be controlled by the distance between the conductor and the charged superamphiphobic surface. The manipulated droplet is positively charged owing to its contact with and separation from the superamphiphobic surface. The sustained triboelectric process between the droplet and surface enables prolonged and functional droplet manipulation. The charged droplet can directly enable the chemical oxidation processes within the droplet. This provides the conditions for developing a microfluidic manipulation platform with specific functions.