Electrocapillary bridge formation from emulsions

Abstract

Abstract Liquid bridges formed under electric fields are well known in polar liquids such as water, whereas their formation in nonpolar oils is generally challenging. In this work, we show that electric-field-induced liquid bridges can readily form from oil-in-oil emulsions. Silicone–castor oil emulsions confined in a film–air–film geometry between parallel ITO electrodes generate multiple bridges under DC electric fields that are lower than those required for the corresponding pure oils. Bridge formation depends strongly on both electric field strength and emulsion mixing ratio. The number of bridges generally increases with increasing castor-oil fraction, while the threshold electric field exhibits a non-monotonic dependence on emulsion mixing ratio and reaches its lowest values at intermediate mixing ratios. For all bridge-forming mixing ratios, the induction time decreases rapidly with increasing electric field. Primary bridges form as coaxial core–shell structures composed of two oil phases. These findings suggest that dispersed droplets can strongly modify electrocapillary instabilities and facilitate electrically induced connectivity in low-polarity liquids that do not form bridges in their homogeneous state.