Induced-charge electroosmosis for rapid mixing of reactive precipitation systems to obtain small and uniform particles

Abstract

The control of product quality in precipitation systems is often difficult due to high supersaturation levels and fast kinetics. Rapid and uniform mixing of fluids is required to minimize supersaturation gradients before the onset of nucleation. This study proposes an active mixing platform utilizing induced-charge electroosmosis (ICEO) to better control crystal quality attributes such as the size distribution. The mixing performance of the ICEO-based micromixer is characterized through experiments as a function of the solution properties and the electric field parameters such as phase angle, frequency, and voltage. Optimal mixing is achieved at lower conductivities when the phase difference is 180°. Furthermore, computational fluid dynamics simulations demonstrate that uniform supersaturation is achieved at shorter mixing lengths of the device along with a narrower residence time distribution in the presence of ICEO. Additionally, the performance of the ICEO-based crystallizer is demonstrated for the reactive precipitation of silver chloride particles and carbamazepine-succinic acid cocrystals. The application of ICEO leads to the production of smaller silver chloride particles with a narrower size distribution and an improved yield for cocrystallization compared to cases without ICEO. The ICEO-based micromixer characterized in this work is generally attractive for the continuous production of particles through reactive precipitation with stringent requirements on product uniformity and yield.