Microfluidic Step Emulsification with Parallel Nozzles on a Vertical Slit

We introduce a novel step emulsification device comprising parallelized channels intersecting a vertical slit, aimed at mitigating issues like nozzle blockage and unwanted droplet coalescence, by guiding the continuous phase flow effectively. This directed flow efficiently carries droplets away from the nozzles arrayed along a vertical slit toward an outlet, significantly reducing the droplet residence time. Employing slit devices with 16 and 128 parallel nozzles, averaging 15.8 μm in height and 107 μm in width, we achieved monodisperse droplets with average sizes of 63 and 68 μm and a coefficient of variation below 5% at production rates of 0.35 and 3.6 mL per hour, respectively. This advancement represents a significant step forward in addressing the challenges of step emulsification, promising enhanced control and consistency of droplet size at various production scales.