Comparison of three droplet microreactors for the continuous production of nano and micro particles

Abstract

In this study we compare three droplet microreactors for the synthesis of cerium oxide nanoparticles (CONs) and calcium phosphate crystals (CaPs) and discuss their suitability for long-term, continuous operation. The synthesis conditions were controlled by manipulating the flow rate ratio of the continuous phase to the dispersed (Qc/Qd), which is a crucial factor influencing droplet formation rate (DF) and droplet size. After identifying appropriate operating conditions (droplet size between 400 and 500 μm), synthesis experiments were conducted to test the continuous operation of the microreactors. Among the three designs, one flow focusing device with a buffer stream, demonstrated superior resilience to particle fouling, and seemed to be appropriate for long-term, continuous particle synthesis. Particles synthesized using microfluidics were consistently smaller and exhibited less crystallinity than those produced during conventional batch synthesis due to the short residence time in the microreactor.