Surfactant stabilized water-in-oil droplets are produced in the flow-focusing junction of the droplet production device (Fig. ). The continuous phase comprises 1, 3 and 5 wt% perfluoropolyether-polyethylene glycol (PFPE-PEG) block-copolymer fluorosurfactant (Ran Biotechnologies, Inc., USA) dissolved in fluorinated oil (HFE-7500, 3M, USA). The dispersed phase is pure Milli-Q water. Both phases are injected into the production device with syringe pumps (11 PicoPlus Elite, Harvard Apparatus, USA). The fluids are loaded into 1 mL syringes (OmnifixÒ-F, B.Braun, Germany) and connected to the device by a cannula (StericanÒ, 0.4 x 20 mm 2 , BL/LB, B.Braun, Germany), and PTFE-tubing (0.4 x 0.9 mm, Bola, Germany). The flow rates for the oil and aqueous phases are set to 400 and 200 µl/hr, respectively and the produced droplets are collected in an Eppendorf tube (Eppendorf, Germany)