Diffusion-Controlled Nucleation, Growth, and Self-Assembly of Silica Nanoparticles in Laminar Microfluidic Flow

Microfluidic devices have emerged as a promising platform for controlling small fluid volumes at the micrometer scale, offering new opportunities in several areas, especially in the synthesis of nanomaterials such as SiO₂ nanoparticles. This potential is related to the precise control of synthesis parameters such as temperature, reagent concentration, flow rate, and micromixing, which are difficult to control in batch synthesis. Furthermore, the spatial confinement regime can facilitate the separation of nucleation and growth steps, providing superior control over particle size and dispersion. However, their operability under challenging conditions, such as high reagent concentrations, and the mechanisms governing synthesis, growth, and self-assembly remain insufficiently understood. Therefore, this study compares microfluidic and batch syntheses of SiO₂ nanoparticles. Through numerical simulations of laminar flow and species advection diffusion, we map the precursor overlap along the microchannel, including the identification of a narrow interdiffusion region where nucleation is expected to initiate. The role of flow in the formation of new self-assembled structures is also discussed, as consistent with the size-dependent hydrodynamic characteristics of particles under laminar convection and enhanced by confinement.