Electrocoalescence Mechanisms of Microdroplets Using Localized Electric Fields in Microfluidic Channels

Electrocoalescence of water-in-oil microdroplets in microfluidic channels is an active technique that enables droplet-based mixing functionalities to be achieved in lab-on-a-chip applications. In this work, a characterization of the electrocoalescence mechanisms of water microdroplets in oil is presented, using localized electric field systems. We report a theoretical and experimental description of the electrocoalscence behavior of droplet pairs by varying the physical and fluid dynamic conditions of the phases. Our results demonstrate that localized electric field systems can be reliably used to merge droplets in pairs, regardless of the distance between the drops. The coalescence behavior was dependent upon the viscosity of the continuous phase for water droplets that were separated by a thick layer of oil and upon interfacial tension for droplets that were in close proximity. We showed that these systems have the potential to be used for high-throughput applications and that, unlike other examples of active systems in the literature, the need of droplet synchronization and the application of high voltages is considerably reduced.