(570d) Microchemical Synthesis Facilitated by Microfluidic Distillation
Microchemical systems have evolved from simple devices for basic chemistry to more complex systems for multi-step synthesis. Enhanced heat and mass transfer characteristics, safer synthesis of dangerous compounds, isolation of air and moisture sensitive chemistry, and reduction of hazardous waste all are realized using microreactors. Optimized reaction conditions and rapid experimentation also add value to the technology by shortening product development life cycles. These reasons and others have provoked interest in continuous-flow synthetic chemistry using microreactors. Traditional batch synthetic transformations utilize separations to purify, switch solvents, and isolate products during work-up. Separations are, therefore, central in carrying out synthetic chemistry and examples include liquid-liquid extraction, filtration, evaporation, and distillation.
Distillation is a ubiquitous method of separating liquid mixtures based on differences in volatility. Performing such separations in microfluidic systems is difficult because interfacial forces dominate over gravitational forces. We describe distillation in microchemical systems and present an integrated silicon device capable of separating liquid mixtures based on boiling point differences. Microfluidic distillation is realized by establishing vapor-liquid equilibrium during segmented flow. Enriched vapor in equilibrium with liquid is then separated using capillary forces, and thus enabling a distillation operation. Design criteria for operation of on-chip distillation is set forth, and the working principle demonstrated by separation of binary liquid mixtures. What is more, microfluidic distillation is applied to enable continuous-flow synthesis of chemistry relevant to pharmaceutical development.