  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.
