Effect of cross-slot configuration in microfluidics on o/w emulsification at high throughput
Résumé
The Liquid–liquid dispersion process is experimentally investigated to manufacture oil-in-water emulsion working at high flowrates in the cross-slot type of microfluidics. Two cross layouts, namely symmetric and asymmetric configurations, are compared via characterizing the droplet size and size distribution. Automated granulometry is implemented on the images taken by microscopy observations of the emulsion samples. High-speed shadow photography is carried out to discover the continuous- and dispersed-phase flow interactions in the vicinity of the collision region. The results show that the designed microsystems present great potential in terms of fabricating fine oil droplets distributed in the final emulsion. The arithmetic averaged diameter is less than 10 μm at all tested flow conditions and the minimum mean diameter reaches 3.9 μm at the highest energy consumption case. Because of the higher shear stress and more intensified interaction, the symmetric geometry of the cross-slot is beneficial to create fewer amounts of large droplets and dispersing the oil phase more uniformly at the same hydrodynamic conditions, especially in the low Reynolds flow case in this study. As the flowrate is enhanced, the disparity between them is diminished due to the instability inside the channel reaching a high level. The mean drop diameter for both systems is capable to be scaled with the emulsion velocity-based Weber number. The detrimental effect of the symmetric configuration is that the energy required to burst the dispersed streams is relatively a little higher than with asymmetric one.
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