Charged drop impinging on particles dispersed over a metallic plate: A method of particle cleaning

Abstract

An electric field applied to a droplet impinging on a hydrophobic surface has an extensive variety of applications, including ant-icing, heat transfer enhancement, self-cleaning, droplet manipulation, and electrostatic spraying. The present study demonstrates an effective method of particle removal using a charged droplet. This method employs a pin-plate electrode setup to investigate the dynamics of a charged droplet impact on the surface covered with particles. The particles of different properties such as wettability, electrical conductivity, etc. have been used. Silane-coated glass beads, carbon black, and glass beads are dispersed over the ground copper electrode. The applied potential is also varied from 2 kV to 4 kV. A high-speed imaging is employed to visualize the drop motion, dynamic behavior, and self-cleaning phenomenon. The experimental results indicate that drop generation and impact occur at applied potentials of 2.5, 3, and 3.5 kV, in contrast, at 2 kV, there is no droplet pinch-off. At 4 kV, electric breakdown and bridging of the droplet between the capillary and ground electrode are observed. The drop impact on the silane-coated glass bead leads to their attachment due to the adhesiveness of the particles and the droplet. The silane-coated particles are removed from the droplet surface due to the deformation of the drop and the electric repulsive force. In the case of carbon black and glass beads, the particles are captured by the droplet due to the electrostatic force of attraction. Higher electric potentials lead to an increased spreading diameter of the droplet. The higher electric field enhances the contact area between the droplet and the particles, thereby removing more particles.