Creating monodispersed droplets with electrowetting-on-dielectric step emulsification

Abstract

Monodisperse droplets are important in drug screening, and cell-based and biochemical research. However, conventional methods for creating droplets, such as co-flow, T-junction and flow-focusing, have poor monodispersity because of fluctuations in the flow rate. Because step emulsification is based on the principle of Laplace pressure, it is insensitive to the flow rate and yields a constant and high monodispersity. In the present study, we combine electrowetting and step emulsification to reduce the negative influence of flow-rate fluctuations and to prepare highly monodisperse droplets. We demonstrate that the flow rate and voltage applied to the droplets can independently influence the droplet size. This method has great potential in chip-based bioanalysis and cell-based studies where highly monodisperse droplets are needed.