Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

Micromachines

Enrico Chiarello²  Ladislav Derzsi²  Matteo Pierno²  Giampaolo Mistura²  Evandro Piccin³  Andrew deMello¹ 

[1] Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, via Marzolo 8, 35131 Padova, ItalyDipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, via Marzolo 8, 35131 Padova, Italy;Departamento de Química, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil;

关键词: droplet microfluidics;    T-junction;    squeezing regime;    non-Newtonian fluids;    matrix viscoelasticity;    xanthan solutions;    shear-thinning;   

DOI  :  10.3390/mi6121458

来源: mdpi

【 摘 要 】

We have compared the formation of oil drops in Newtonian and non-Newtonian fluids in a T-junction microfluidic device. As Newtonian fluids, we used aqueous solutions of glycerol, while as non-Newtonian fluids we prepared aqueous solutions of xanthan, a stiff rod-like polysaccharide, which exhibit strong shear-thinning effects. In the squeezing regime, the formation of oil droplets in glycerol solutions is found to scale with the ratio of the dispersed flow rate to the continuous one and with the capillary number associated to the continuous phase. Switching to xanthan solutions does not seem to significantly alter the droplet formation process. Any quantitative difference with respect to the Newtonian liquid can be accounted for by a suitable choice of the capillary number, corresponding to an effective xanthan viscosity that depends on the flow rates. We have deduced ample variations in the viscosity, on the order of 10 and more, during normal operation conditions of the T-junction. This allowed estimating the actual shear rates experienced by the xanthan solutions, which go from tens to hundreds of s⁻¹.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.