Fig. 1.

dropFAST integrated platform. (A) For a bacterial sample, dropFAST enables encapsulation of single bacterial cells along with a fluorescent bacterial growth indicator dye and antibiotics into picoliter-sized droplets. This is immediately followed by short on-chip incubation that allow for a few bacterial replications and then in-line fluorescence detection. Empty droplets emit weak fluorescence, while droplets with growing bacteria emit strong fluorescence. Growing bacteria in a sample is then quantified via histogram analysis of droplet fluorescence. (B) Integrated dropFAST device parallelizes droplet generation, incubation, and detection in a continuous flow. The droplet generator consists of a 20 μm flow-focusing region that facilitates stable droplet generation (inset i), followed by a 500-μm-wide incubation zone (inset ii), and finally a 10-μm-wide detection zone that allows for sequential detection of droplets (inset iii). (C) Integrated dropFAST platform includes instrumentation to facilitate heated incubation using a Peltier heater and streamlined fluorescence detection using a laser excitation source and an avalanche photodiode (APD) detector.