Microfluidic emulsion characterization for the development of armored droplet arrays

Abstract

An experimental study was performed to determine the best method for using a flow-focusing device to produce monodisperse water droplets in a polymer flow with sufficient spacing to polymerize a protective shell around the droplets using continuous flow lithography. Contact angle measurements and surface tension measurements were used to determine how wettable the polymer is with respect to water and PDMS. Polymerization reaction kinetics tests were used to determine a suitable polymer for the system. The droplet size and spacing for different flow-focusing devices with different dimensions were characterized to determine the best dimensions. Finally, characterization tests for various polymer and water flow rates were performed to examine the droplet size, spacing, velocity and frequency of production, as well as the fluctuations and instabilities in the system. From these characterization tests it was determined that the best flow systems for armoring droplets arise when the water flow rate is greater than 0.05pL/min, the polymer flow rate is between 0.4 and 1.2pL/min and the flow-rate ration of water to polymer is less than 1:10.