Production of monodisperse water-in-oil emulsions consisting of highly uniform droplets using asymmetric straight-through microchannel arrays

This paper reports the production of monodisperse water-in-oil (W/O) emulsions using new microchannel emulsification (MCE) devices, asymmetric straight-through MC arrays that were hydrophobically modified. The silicon asymmetric straight-through MC arrays consisted of numerous pairs of microslots and circular microholes whose cross-sectional sizes were 10 mu m. This paper primarily focused on investigating the effect of the osmotic pressure of a dispersed phase (I (d)) on MCE. This paper also investigated the effects of the type of continuous-phase oils and the dispersed-phase flux (J (d)) on MCE. The dispersed phases were Milli-Q water and Milli-Q water solutions containing sodium chloride. The continuous phases were decane (as control), hexane, medium chain triacylglyceride (MCT), and refined soybean oil (RSO) solutions containing tetraglycerin monolaurate condensed ricinoleic acid ester (TGCR) as a surfactant. At I (d) of exceeding threshold, highly uniform aqueous droplets with coefficients of variation of less than 3% were stably generated via hydrophobic asymmetric straight-through MCs. Monodisperse W/O emulsions with average droplet diameters between 32 and 45 mu m were produced using the alkane-oil and triglyceride-oil solutions as the continuous phase. This work also demonstrated that the hydrophobic asymmetric straight-through MC array had remarkable ability to produce highly uniform aqueous droplets at very high J (d) of up to 1,200 L m(-2) h(-1).