Three-Fluid Sequential Micromixing-Assisted Nanoparticle Synthesis Utilizing Alternating Current Electrothermal Flow

Multiple micromixing in a controlled sequence is an essential process for complex chemical synthesis of functional nanoparticles with desired physicochemical properties. Herein, we developed a unique sequential micromixing-assisted nanoparticle synthesis platform utilizing alternating current electrothermal flow (ACET). A two-fluid micromixer comprised with pairs of staggered asymmetric electrodes was first designed and characterized by joint numerical simulations and experiments to obtain the optimized electrode configuration within a straight channel. On this basis, an extra pair of symmetric electrodes was added at the main channel entrance to form a three-fluid sequential micromixer. The middle fluid would first mix with the side fluids through the symmetric ACET microvortex pair in the upstream region and then realize the side fluid mixing by the asymmetric ACET microvortex in the downstream region. Rapid and complete mixing in a short channel was observed for a relatively high flow velocity up to 7 mm/s at an AC signal of 27.5 V and 1 MHz. Sequential micromixing was achieved by flexibly adjusting the volume of each fluid and the AC voltage within the three-fluid mixer. Both the two-fluid mixing process and the three-fluid mixing process were applied to synthesize the Co–Fe Prussian blue analogue nanoparticles. In comparison with two-fluid mixing, three-fluid sequential mixing offers nanoparticles with higher dispersion, controlled particle morphology, and more regular shapes. Therefore, the ACET flow-based sequential micromixing strategy can be an alternative for complex chemical and biochemical reactions.