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Step emulsification is a key technique for achieving scalable production of monodisperse emulsion droplets owing to its resilience to flow fluctuations. However, the persistent issue of satellite droplets, an inherent byproduct of main droplets, poses challenges for achieving truly uniform product sizes. In a previous study, we introduced a module with step-emulsifier nozzles upstream and deterministic lateral displacement (DLD) micropillar arrays downstream to generate satellite-free droplets at a low throughput. In this study, we demonstrate an upscaled parallelized setup with ten modules that were designed to produce satellite-free droplets. Each module integrated 100 step-emulsification nozzles in the upstream region with DLD micropillar arrays downstream. We conducted 3D flow simulations to ensure homogeneous distribution of the input fluids. Uniformly supplying an aqueous polyvinyl alcohol solution and an acrylate monomer as continuous and dispersed phases into the ten modules, the nozzles in each module exhibited a production rate of 539.5 ± 28.6 drop/s (n = 10). We successfully isolated the main droplets with a mean diameter of 66 μm and a coefficient of variation of 3.1% from satellite droplets with a mean diameter of 3 μm. The total throughput was 3.0 mL/h. The high yield and contamination-free features of our approach are promising for diverse industrial applications. [ABSTRACT FROM AUTHOR]

Microfluidic post-array devices have the potential to generate quasi-monodisperse emulsion droplets with high throughput and dispersed phase fractions by splitting droplets with regularly arranged posts. However, the lack of understanding of post-array devices makes it challenging to predict droplet size and quantitatively evaluate the influence of post geometry, hindering their widespread application. Therefore, we investigated the characteristics of droplet breakup through a post array using a series of devices with sheath-flow configurations, in which the dispersed and continuous flow rates could be flexibly tuned. Using a poly(dimethylsiloxane)–glass device fabricated via soft lithography, we found that the volume ratio of the dispersed phase to the continuous phase significantly affects the droplet size, even when the viscosity ratio is close to one. For the first time, we demonstrated that the effective capillary number calculated from the emulsion viscosity and effect of the dispersed phase fraction consistently describes various experimental results. Furthermore, our flow observations and droplet diameter measurement showed two breakup modes: the size-constant obstruction and shear-induced modes with a power-law correlation similar to droplet splitting in a T-junction. Thus, the power-law correlation in microfluidic droplet splitting successfully expresses the droplet generation characteristics in post-array devices. A combination of effective viscosity correction and curve fitting allowed us to evaluate the influence of the material and post-geometry on droplet generation characteristics. This study contributes to the understanding of droplet breakup in post-array devices and extends their unique droplet generation properties to include high-throughput, high-fraction, robust, and continuous emulsification processes. [ABSTRACT FROM AUTHOR]