Characteristics of particles deposited on a single free-fall charged droplet

Particles deposited on a free-fall charged droplet were experimentally studied. A droplet, charged under 40% Rayleigh limit, fell through the particle chamber to capture particles by electrostatic attractions. The velocity of the droplet was smaller than 2.1 m/s. The particle-laden droplet eventually spread on a glass slide, which was further analyzed using optical microscope. It was found that the equivalent number of particles captured by the charged droplet were larger than that of uncharged ones by one order of magnitude at least. Remarkably, particles on the charged droplet agglomerated into a large cluster, which indicates that the agglomerated cluster can be actively precipitated due to the gravity force if the droplet completely evaporates. The front side of the charged droplet was the predominant region to capture the particles. However, the actual area of capture was smaller than hemispheric surface.