Generation of water-in-oil and oil-in-water microdroplets in   polyester-toner microfluidic devices
  This paper demonstrates that disposable polyester-toner microfluidic devices are suitable to produce either water-in-oil (W/O) or oil-in-water (O/W) droplets without using any surface treatment of the microchannels walls. Highly monodisperse W/O and O/W emulsions were generated in T-junction microdevices by simply adding appropriate surfactants to the continuous phase. The dispersion in size of droplets generated at frequencies up to 500 Hz was always less than about 2% over time intervals of a couple of hours. 
Evandro Piccin, Davide Ferraro, Paolo Sartori, Enrico Chiarello,   Matteo Pierno, Giampaolo Mistura
cond-mat.mtrl-sci