Relationship between concentration of surfactant and pressure for droplet creation, and effect on droplet size in microchannel O/W emulsification

O/W emulsion was produced with use of microchannels constructed on a single-crystal silicon substrate plate by micromachining technology. The relationship between concentration of surfactant and pressure for droplet generation is studied, and the effect of them on droplet size is also investigated. Triolein and sodium lauryl sulfate (SDS) aqueous solution were used for oil and water phases, respectively. As SDS concentration increases, the interfacial tension between oil and water phases decreases and pressure for droplet generation becomes low, When the SDS concentration exceeds the critical micelle concentration, the interfacial tension and the pressure for droplet generation are constant. A similar phenomena is observed for the SDS solution to which NaCl is added. Average droplet size was 20 mu m and independent of the SDS concentration and pressure. The geometric standard deviation is below 1.03, which indicates monodispersion of droplets.