Abstract
Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phase should be sufficiently fast compared to the outflow of the liquid that is forming the droplet. The ratio of the viscosities was therefore varied by using a range of continuous and dispersed phases, both experimentally and computationally. At high viscosity ratio (η d/η c), the droplet size is constant; the inflow of the continuous phase is fast compared to the outflow of the dispersed phase. At lower ratios, the droplet diameter increases, until a viscosity ratio is reached at which droplet formation is no longer possible (the minimal ratio). This was confirmed and elucidated through CFD simulations. The limiting value is shown to be a function of the microchannel design, and this should be adapted to the viscosity of the two fluids that need to be emulsified.
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Acknowledgments
This research project is part of the Microdruppels project, in which we collaborate with Nanomi, FrieslandCampina, and Demcon amongst others. The project is financially supported by the Dutch Ministry of Economic Affairs and the Dutch provinces of Gelderland and Overijssel. Koen van Dijke and the Food Process Engineering group of Wageningen University want to thank the National Food Research Institute and the University of Tsukuba for their hospitality and willingness for cooperation.
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van Dijke, K., Kobayashi, I., Schroën, K. et al. Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification. Microfluid Nanofluid 9, 77–85 (2010). https://doi.org/10.1007/s10404-009-0521-7
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DOI: https://doi.org/10.1007/s10404-009-0521-7