Hfe7500 fluorinated oil

Picoinjected droplets were reinjected into a droplet-sorting device (Supplemental Fig. S6) and spaced with surfactant-free HFE-7500 fluorinated oil. Flow rates were adjusted so that droplets were reinjected at a frequency of ∼300 Hz. Droplets were detected by their orange fluorescence and sorted based on their blue (concentration of picoinjected substrate) and green (concentration of product) fluorescence. The 1% most green fluorescent droplets having received the correct amount of substrate were gated (Fig. 2I) and deflected into the recovery channel by applying a 1200 V AC (30 kHz) electric field using a high voltage amplifier (Ahn et al. 2006 ; Baret et al. 2009 (link)). Sorted droplets were collected in an Eppendorf tube via a length of PTFE tubing. At the end of the process, the recovered oil/droplet mixture was successively supplemented with 200 µL of HFE 7500 fluorinated oil, 100 µL of 1H,1H,2H,2H-perfluoro-1-octanol (Sigma-Aldrich) and 200 µL of 200 µg/mL yeast total RNA solution (Ambion) by flushing the reagent through the PTFE tubing. The mixture was finally mixed by vortexing and briefly centrifuged. The upper aqueous phase was then recovered and transferred into a new tube.