Emulsion electrocoalescence in microfluidics: impact of local electric fields.

The mechanism of coalescence of aqueous droplet pairs under an electric field is quantitatively studied using microfluidics in quiescent conditions. We experimentally trap droplet pairs and apply electric fields with varying frequencies and formulation compositions. We find that the electrical resistance of the oil used as continuous phase controls the onset of electrocoalescence in quiescent conditions. We observe that the local field enhancement between droplets strongly depends on formulations but also on the number of droplets across the electrodes. These findings provide a better understanding of the onset of electrocoalescence and pave a route towards the rationalization of droplet-based microfluidics operations.