Microfluidic-based synthesis of monodisperse silica microparticles with widely tunable size and minimized channel clogging

Silica microparticles are widely used in various fields, including chromatography, catalysis, and drug delivery systems, owing to their excellent intrinsic properties and micrometer-scale. To improve product quality and reproducibility, it is necessary to develop a preparation method for monodisperse silica microparticles with tunable size. Although monodisperse silica microparticles can be prepared using microfluidic devices, silica gel tends to form in premixed reaction precursor solutions over time, leading to clogging of the flow channels. This paper reports a preparation method for monodisperse silica microparticles across a wide size range while mitigating channel clogging. Specifically, monodisperse droplets of an aqueous sodium silicate solution were generated using a microfluidic device and subsequently reacted with an aqueous sodium bicarbonate solution outside the device. By adjusting the flow channel dimensions, gas pressure for the aqueous phase flow, and oil phase flow rate, monodisperse silica microparticles were successfully prepared over a size range spanning two-orders-of-magnitude.