Manipulation of Oil Droplets in O/W Emulsion Flow in Bifurcating Channel by Electric Field

Abstract

Manipulation of oil droplets in O/W emulsion flow in bifurcating channel by externally applied electric field is experimentally attempted. The oil droplets in the O/W emulsion are charged with positive electricity in advance by adding cationic surfactant. Positive and negative electrodes are installed in both sides of the channel just before the bifurcating region to generate an electric field in spanwise direction. In the region where electric field is applied, positively charged oil droplets flow toward the negative electrode located in right-hand side of the channel. Oil droplets finally tend to be directed to the right-hand side branch at the bifurcation. Rate of number of oil droplets directed to the right-hand side branch increases with increase of the concentration of the cationic surfactant as long as the concentration is less than critical micelle concentration (CMC) of the cationic surfactant. When the concentration exceeds CMC, the rate keeps almost constant. This may because the surface of the droplet is fully covered by the surfactant when the concentration exceeds CMC.