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Microuid Nanouid (2014) 17:711720 DOI 10.1007/s10404-014-1348-4
RESEARCH PAPER
Y- and T-junction microuidic devices: effect of uids and interface properties and operating conditions
F. Y. Ushikubo F. S. Birribilli
D. R. B. Oliveira R. L. Cunha
Received: 26 September 2013 / Accepted: 18 January 2014 / Published online: 6 February 2014 Springer-Verlag Berlin Heidelberg 2014
Abstract Water-in-oil emulsions were produced in microchannels with Y- and T-junction geometries by individual droplet generation. For each microchannel conguration, the effect of the uids and interface properties as well as of the process conditions was evaluated. The size of the droplets depended mainly on the relative velocity between continuous and dispersed phases and the relative uid viscosity between phases. Those variables were related to the shear stress between the phases, which caused the droplet detachment. In addition, the interfacial forces played a minor role in Y-junction, and they had no effect in the droplets formation in T-junction microchannels. In Y-junction, a large variation in the droplet size was observed, depending on the system composition and the operating conditions. At low relative velocity and uid viscosity, no droplets were generated. In contrast, the process in T-junction resulted in a lower variation of droplets size and the droplets were formed even at less favorable conditions. Such results indicate that the knowledge of the mechanism of droplets generation in each microchannel geometry makes it possible to choose the appropriate conguration according to the type of uid, and the operating conditions can be adjusted to obtain the desired nal emulsion.
Keywords Emulsion Microuidic devices
Droplet generation Y-junction microchannel
T-junction microchannel
1 Introduction
The use of microuidic devices is a promising technique for the production of highly monodispersed emulsions, since droplets are formed individually at the junction of the dispersed and continuous phases. With this high control in the droplets generation, the coefcient of variation, which represents the droplets size polydispersity, can be lower than 5 % (Vladisavljevi et al. 2012). The emulsion monodispersity hinders the Ostwald ripening phenomenon, which is the growing of a larger droplet at expense of a smaller one (Sugiura et al. 2004). With more homogeneous droplet size, more stable emulsions are obtained.
An additional advantage of the emulsication through microuidics is that the droplets generation is smoother than in conventional...