Effect of moderate DC electric field on formation of surfactant-laden drops

Abstract

The continuous formation of mm-scale surfactant-laden aqueous drops in oil was studied under an applied DC electric field of 0–267 kV/m. The parameters varied included the flow rate of dispersed phase, the electric field strength, the viscosities and densities of dispersed and continuous phase and the surfactant type (anionic or cationic) and concentration. An increase in the electric field strength resulted in a decrease of the drop size due to increasing stresses on the drop interface. The size reduction continued until transition to the irregular regime. The values of critical electric field strength for this transition increased with an increase in both the flow rate and the viscosity ratio between the dispersed and continuous phase. The critical electric field strength and the size of the drops formed in the periodic dripping regime were independent of the electric field polarity. The effect of the electric field increased with a decrease of interfacial tension and density difference between the dispersed and continuous phase.