Highly Parallel Three-Dimensional Microfluidic Systems for Manufacturing Catalytic Nanoparticles

University Of Southern California, Los Angeles CA

Investigators

Abstract

The unique biological, optical, and chemical properties of metal nanoparticles have driven several decades of research into their many potential applications. If these applications are to be realized at a level that will make a significant societal impact, cost-effective techniques for producing industrially relevant quantities of nanoparticles must be developed. Today, chemical manufacturing techniques for high quality nanoparticle fabrication remain at small production scales, with a cost that reflects the limited throughput and labor intensity of a by-hand process. This is because only small-scale chemical reactions can achieve uniform mixing conditions and uniform temperatures throughout the reaction vessel, which are essential conditions for producing uniform, high-quality nanoparticles. Standard, large-volume industrial chemical reactors lack uniform mixing and temperature distribution tend to produce low-quality particles and are therefore an inappropriate route to the scale-up of high-quality nanoparticle manufacturing, for example, for catalysis. This award investigates continuous-flow chemical micron scale reactors as a means to maintain the small-scale conditions necessary to make high-quality nanoparticles while allowing for continuous processing that can be automated and operated around the clock. Further, to scale these microreactors to industrially relevant conditions, this research investigates massive parallelization, i.e., the controlled operation of many microreactors at once to produce large quantities of high-quality nanoparticles. This research effort is coordinated with an outreach program that integrates community college students into research, and makes science and engineering careers accessible to these students, especially women and minority students. High quality nanoparticles for commercial purposes are still prepared at the lab scale, essentially by hand. The limit to scale-up is the fact that in solution-phase chemical techniques, the size and monodispersity of the resulting nanoparticles are extremely sensitive to the reaction temperature and reagent mixing conditions. It is impossible to maintain the necessary uniformity in current industrial-scale reactors even with stirring. Microfluidic reactors, however, have inherently good thermal uniformity and droplet microfluidic systems allow for rapid mixing and homogenization. This research approach relies on ionic liquid (IL)-based nanoparticle synthesis in microfluidic reactors. In these reactors, droplets of IL are separated in a fluorocarbon oil-based carrier stream. The microfluidic system developed in this research will operate at remarkably high colloid concentrations, nearly 50-100 mg nanoparticles/mL reaction solvent, compared to nearly 2 mg/mL for traditional solution phase approaches. In the nanomanufacturing system studied here, a microreactor system is scaled to sixteen parallel channels. The funded work is a science-based investigation of the key system parameters, such as, process monitoring and feedback control, that must be addressed to scale such a parallel system to an arbitrarily large capacity.