Production and Characterization of Monodispersed Oil-in-Water Microspheres Using Microchannels.

Oil-in-water (O/W) microspheres (MS) were produced using microchannels (MC) of different channel size and type formed on a single-crystal silicon substrate, and the fundamental properties for the MS generation were studied. Sunflower oil containing sorbitan monolaurate as surfactant was used. MC of 5.3 μm in equivalent diameter gave an average 20 μm diameter of the produced O/W-MS. The coefficient of variation of the MS was below 2% with the surfactant concentration less than 0.5 wt%. The average diameter and the coefficient of variation of the MS changed little over 60 days, indicating high stability against coalescence. Horizontally setting the MC of 8.5 μm similar to that of 5.3 μm, the monodispersed MS were difficult to produce because of their coalescence and expansion near the channels. Changing MC from horizontal to vertical type, the monodispersed MS could be produced continuously by utilizing the buoyancy.