Figure 6.

Representation of a droplet generator module of a microfluidic screening platform. Aqueous stream 1 contains the fluorogenic substrate which can be supplemented with lysis reagents. The stream is combined with aqueous stream 2, which carries a suspension of cells displaying, expressing or secreting the protein of interest and variants thereof, or a PCR mixture (in vitro systems). The water-in-oil droplets are formed at a flow-focusing junction and move into an incubation line. Droplets carrying active variants are shown in green. The incubation line is either directly connected to the next module of the platform (sorting module, Figure 6) or it is intersected with an additional module—the droplet fusion device (not depicted)—which enables modification of preformed droplets [59,64,65,68,69,70].