Measurement of charge of a droplet induced by contact electrification

The contact electrification is the charge transfer between two surfaces by contact and separation. We have developed the experimental method to measure the amount of charge of a droplet induced by contact electrification. In the method, the uniform electric field is applied to a droplet suspended in dielectric oil. The horizontal movement of a droplet is determined by the balance between electric and drag force. The drag force exerted on a droplet has been calculated by Hadamard-Rybczinski solution. The effects of a droplet size, electrolyte concentration of an aqueous droplet on the amount of charge have been examined.