Simultaneous generation of multiple aqueous droplets in a microfluidic device

This paper describes a microfluidic platform for the on-demand generation of multiple aqueous droplets, with varying chemical contents or chemical concentrations, for use in droplet based experiments. This generation technique was developed as a complement to existing techniques of continuous-flow (streaming) and discrete-droplet generation by enabling the formation of multiple discrete droplets simultaneously. Here sets of droplets with varying chemical contents can be generated without running the risk of cross-contamination due to the isolated nature of each supply inlet. The use of pressure pulses to generate droplets in parallel is described, and the effect of droplet size is examined in the context of flow rates and surfactant concentrations. To illustrate this technique, an array of different dye-containing droplets was generated, as well as a set of droplets that displayed a concentration gradient of a fluorescent dye. (C) 2008 Elsevier B.V. All rights reserved.