Production characteristics of uniform large soybean oil droplets by microchannel emulsification using asymmetric through-holes

The aim of this study was to investigate the production characteristics of large soybean oil droplets dispersed in an aqueous solution containing an emulsifier using newly designed microchannel emulsification (MCE) chips. The silicon MCE chips consisted of numerous asymmetric through holes with a characteristic cross-sectional size of 20 μm to 50 μm, each consisting of a microslot and a circular microchannel (MC). MCE using such chips enabled the stable production of uniform large droplets with average diameters of 75 μm and 179 μm respectively, and a coefficient of variation below 2%. The detachment behavior of the large droplets generated from the asymmetric through holes was analyzed and discussed based on results obtained by real-time optical microscopy. The size of droplets smaller than 100 μm was independent of the flow rate of the cross-flowing continuous phase (Qc) applied in this study. In contrast, the size of droplets larger than 100 μm became sensitive to Qc in its range over a critical value. Large droplets with a very narrow size distribution were obtained at dispersed phase fluxes (Jd) of 50 L m-2 h-1 or less, whereas their average diameters were somewhat dependent on Jd.