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Microfluidic technologies are reliable methods to obtain uniform and tiny droplets, but their application is limited by the capacity of single microchannel and the difficulty in fabrication and operation of large amounts of parallel droplet generators. Here, we reported a microchannel device equipped with multiple capillaries for rupturing the dispersed fluid, which realized droplet generation frequency up to 40 kHz in a single microchannel. The microchannel was operated under jetting flow, which was robust for controlling the droplet size uniformity; therefore, the device did not need highly precise machinery and accurate installation during fabrication. 30–100 μm droplets with CV

Liquid-liquid dispersion coupled with droplet formation and mass transfer of surfactants is one of the most typical phenomena in many chemical processes. As in every aspect of this process, the interfacial tension variation caused by the unsaturated adsorption of surfactants on the droplet surface plays an important role. This article focuses on microdroplet formation and the dynamic interfacial behavior of surfactants in the jetting regime. In a capillary embedded step T-junction device, controllable preparation of monodisperse droplets is achieved, and a correlation for predicting droplet sizes is established. A method for measuring the dynamic interfacial tension is provided. Mass transfer coefficients are then calculated for Tween 20 during the droplet formation process by a semiempirical correlation. The results indicate that dynamic interfacial tensions are lower than those obtained when the surfactant is adsorbed to equilibrium. Based on the tip-streaming phenomenon, mass transfer coefficients for Tween 20 can reach up to ∼10-3 m/s, higher than those obtained in coaxial microfluidic devices. All the preliminary results shed light on the nature of droplet formation and will be of significance for application in industrial apparatuses.