  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.
