Effect of droplet-induced fluid motion on the interphase synthesis of nanoparticles in a microfluidic reactor

Abstract: Droplet-based interphase synthesis provides means to produce nanoparticles with low polydispersity by controlling mass transport through droplet dynamics. An experimentally validated model, based on coupled computational fluid dynamics with population balance equation is proposed. The model incorporates: (i) hydrodynamics and thermal-transport of droplet-laden flow, (ii) spatial variation of species concentration with interfacial mass transfer and (iii) a tertiary phase within droplets to capture evolution of particle size distribution (PSD). We conclude that, mixing both inside and outside the droplets controls the PSD (arithmetic mean diameter (D10), ~ 50 nm).Consequently, as spherical-droplet diameter increases from 71% to 96% of the channel diameter (812 {\mu}m), coefficient of variation (CV=standard deviation/mean diameter) of PSD decreases from 33% to 21.3%, implying less polydisperse nanoparticles, due to altered mixing. With non-spherical drops, CV is further reduced to only 11%, which is significantly lower compared to that of 40% in single-phase micro-reactor, suggesting benefit of former.