In this paper, we present a methodology to calculate interfacial tension of a water-oil interface under an electric field. The Young-Laplace equation, conventionally used to estimate surface/interfacial tension in axisymmetric drop shape analysis (ADSA), is modified to include electrostatic effects. The solution needs normal component of the Maxwell stress at the interface which is calculated separately by solving the Laplace equation for electric potential. The optimized fitting between the resulting theoretical profile and the experimentally obtained profile results into Bond number which is used to calculate the apparent value of interfacial tension. The algorithm can process a large number of drop profiles in one go. The methodology can be applied in the ADSA studies for adsorption dynamics where a drop is held for a long time while surface active molecules are allowed to adsorb. The method discussed in this paper will help the future studies in adsorption dynamics at fluid interfaces under electric field and the resulting interfacial property evolution.
Keywords: Young–Laplace equation; axisymmetric dropshape analysis; electrohydrodynamics; interfacial tension; tensiometry.