Combining parallelized emulsion formation and sequential droplet splitting for large-scale polymer microgel production

With the rise of particle-based material systems in life and materials sciences over the past years, high-throughput microfluidics has gained tremendous interest as a simple fabrication method for large quantities of tailored emulsions and microparticles. Here, we present the fabrication of microfluidic systems that combine parallelized droplet formation with sequential droplet splitting by 3D printing via projection-microstereolithography for large-scale production of water-in-oil emulsions and polymer microparticles. The process of droplet splitting is investigated in a 3D-printed single-channel, flow-focusing device and then integrated into a microfluidic system with N = 3 × 20 parallelized channels with individual channel cross-sections of 60 μm. The arrangement of the integrated functional microfluidic elements is evaluated for different orientations to the 3D printing direction. Furthermore, emulsion droplet size adjustment for flow-focused and parallelized microfluidic systems is studied. For a proof-of-concept, the 3D-printed microfluidic system is used to fabricate water-in-oil emulsions and fluorescently labeled, thermally crosslinked poly(acrylamide) microparticles. With that, our platform provides a straightforward and time-efficient path toward microgel production in the size range of 140–170 μm on a milliliter-per-hour scale combining droplet formation parallelization and three integrated droplet splitting stages.