Microfluidic Synthesis of Colloidal Silica

TLDR

Laminar flow reactors suffer from axial dispersion at high linear velocities, producing wide particle size distributions. The study demonstrates the design, fabrication, and operation of microfluidic reactors for synthesizing colloidal silica particles. Two reactor configurations—laminar flow and segmented flow—were examined, and particle size and distribution were analyzed as functions of flow velocity and residence time, with segmented flow achieved by gas‑induced liquid plugs separated by inert gas bubbles. Internal recirculation within liquid plugs eliminates axial dispersion, yielding a narrow size distribution of silica nanoparticles.

Abstract

We demonstrate the design, fabrication, and operation of microfluidic chemical reactors for the synthesis of colloidal silica particles. Two reactor configurations are examined: laminar flow reactors and segmented flow reactors. We analyze particle sizes and size distributions and examine their change with varying linear flow velocity and mean residence time. Laminar flow reactors are affected by axial dispersion at high linear velocities, thus leading to wide particle size distributions under these conditions. Gas is used to create a segmented flow, consisting liquid plugs separated by inert gas bubbles. The internal recirculation created in the liquid plugs generates mixing, which eliminates the axial dispersion effects associated with laminar flow reactors and produces a narrow size distribution of silica nanoparticles.