Effect of surfactants on drop formation flow patterns in a flow-focusing microchannel

The formation of droplets in an immiscible liquid the presence different surfactants was studied experimentally using a flow-focusing microchannel. A low viscosity silicone oil (4.6 mPa s) used as continuous phase and mixture 48% w/w water 52% glycerol dispersed phase. cationic (CMCDTAB = 20 mM), anionic (CMCSDS 11 non-ionic (CMCTX100 3.5 mM) surfactant were added aqueous phase, at several concentrations. Five patterns drop identified, namely squeezing, dripping, jetting, threading tip streaming/jetting, whose boundaries affected by type concentration. Using dynamic interfacial tension values, it possible to plot universal flow pattern map with capillary numbers two phases coordinates, where transition between dripping jetting collapsed for all fluid systems considered, including solutions without surfactants.