Effect of cross-slot configuration in microfluidics on o/w emulsification at high throughput

Abstract

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. Highspeed 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 𝝁𝝁𝝁𝝁 at all tested flow conditions and the minimum mean diameter reaches 3.9 𝝁𝝁𝝁𝝁 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 attributed to the instability inside the channel reaches 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.

Easy Generation of Droplets in a Capillary Inserted Microchannel

“…The continuous phase was sunflower oil (density ρ c = 922 kg/m 3 which ranges from 5.69 to 106.9, indicating that the inertia effect should be considered in this study.…”

“…Droplet microfluidics has become an important branch of microfluidic systems in recent years due to its unique microscale effects and hydrodynamic properties. − Compared with traditional droplet preparation methods, such as high-speed stirring method, layer-by-layer assembly method, and bulk emulsification method, droplets generated using microfluidics have the advantages of a uniform size, good monodispersity, small volume, large surface-to-volume ratio, and high reaction efficiency. − Therefore, droplets in microchannels can be used as microreactors and have a wide range of applications. − To date, droplet microfluidics has become a versatile platform for scientific research and engineering applications in many fields, − such as high-throughput screening in drug development, chemical analysis, single-cell manipulation, and biomedical analysis. − …”

An easy droplet-generation method using an inserted glass capillary into a microchannel

“…Droplet microfluidics has become an important branch of microfluidic systems in recent years due to its unique microscale effects and hydrodynamic properties (Kovalchuk et al 2019;Ji et al 2021).…”