An Ultra-High-Throughput Flow-Focusing Microfluidic Device for Creation of Liquid Droplets in Air

In this paper a new microfluidic technique is proposed for ultra-high-throughput generation of micron-sized water droplets using a high-speed air. We use a 3D flow-focusing microchannel fabricated in PDMS by multilayer lithography process. The interaction of liquid and gas created three main flow conditions which are: Flooded, Dripping, and Jetting. We characterize the Jetting regime where a capillary jet surrounded by the air breaks up into uniform array of droplets. Frequency of generation and droplet size are reported for the jetting regime under different liquid and gas flows. It was possible to obtain 25μm diameter droplets and much higher frequencies (f≈120 kHz) compared to the state-of-the-art microfluidic systems. We believe the advantages of this platform enables many novel applications such as high-throughput screening of airborne targets and large-scale production of oil-free particles. The 3D structure of this device also eliminates the limitation of the conventional droplet-based microfluidic systems, namely clogging issues due to particle aggregation.