Formation mechanism and size prediction of bubble in opposite-flowing T-shaped microchannel

Abstract

Bubble formation in an opposite-flowing T-shaped microchannel with 40 μm in depth and 120 μm in width was real-time visualized and investigated experimentally by means of a high speed camera. N₂ bubbles were generated in glycerol-water mixtures with different concentrations of surfactant sodium dodecyl sulfate (SDS). And the images were captured by the high speed camera linked to a computer. Results indicated that the bubble formation process can be distinguished into three consecutive stages, i.e., expansion, collapse and pinching off. The bubble size decreases with the increase of liquid flow rate and viscosity of liquid phase as well as the decrease of gas flow rate. The surface tension of the liquid phase has no measurable influence on the bubble size. Moreover, a new approach to predicting the size of bubbles formed in the T-shaped microchannel is proposed. And the predicted values agree well with the experimental data.

Keywords

microchannel / bubble formation / high speed camera / opposite-flowing

References

[1] Chan E. M., Alivisatos A. P., Mathies R. A. High-temperature microfluidic synthesis of CdSe nanocrystals in nanoliter droplets[J]. Journal of the American Chemical Society, 2005, 127(40): 13854-13861.

[2] Dittrich P. S., Manz A. Lab-on-a-chip: Microfluidics in drug discovery[J]. Nature, 2006, 5(3): 210-218.

[3] Yue J., Chen G. W., Yuan Q. Hydrodynamics and mass transfer characteristics in gas-liquid flow through a rectangular microchannel[J]. Chem Eng Sci, 2007, 62(7): 2096-2108.

[4] Fuerstman M. J., Garstecki P., Whitesides G. M. Coding/decoding and reversibility of droplet trains in microfluidic networks[J]. Science, 2007, 315(5813): 828-832.

[5] Anna S. L., Bontoux N., Stone H. A. Formation of dispersions using “flow focusing” in microchannels[J]. Applied Physics Letters, 2003, 82(3): 364-366.

[6] Cubaud T., Tatineni M., Zhong X., et al. Bubble dispenser in microfluidic devices[J]. Phys Rev E, 2005, 72(3): 037302.

[7] Gañán-Calvo A. M., Gordillo J. M. Perfectly monodisperse microbubbling by capillary flow focusing[J]. Physical Review Letters, 2001, 87(27): 274501.

[8] Yasuno M., Sugiura S. Monodispersed microbubble formation using microchannel technique[J]. AIChE J, 2004, 50(12): 3227-3233.

[9] Xu J. H., Li S. W., Chen G. G., et al. Formation of monodisperse microbubbles in a microfluidic device[J]. AIChE J, 2006, 52(6): 2254-2259.

[10] Garstecki P., Fuerstman M. J. Formation of droplets and bubbles in a microfluidic T-junction: Scaling and mechanism of breakup[J]. Lab on a Chip, 2006, 6(3): 437-446.

[11] van Steijn V., Kreutzer M. T., Kleijn C. R. μ-PIV study of the formation of segmented flow in microfluidic Tjunctions[ J] Chem Eng Sci, 2007, 62(24): 7505-7514.

[12] Jia Z. J., Fang Q., Fang Z. L. Bonding of glass microfluidic chips at room temperatures[J]. Anal Chem, 2004, 76(18): 5597-5602.

[13] Xu J. H., Luo G. S., Li S. W., et al. Shear force induced monodisperse droplet formation in a microfluidic device by controlling wetting properties[J]. Lab on a Chip, 2006, 6(1): 131-136.

[14] Garstecki P., Stone H. A., Whitesides G. M. Mechanism for flow-rate controlled breakup in confined geometries: A route to monodisperse emulsions[J]. Physical Review Letters, 2005, 94(16): 164501.

[15] Xiong R., Bai M., Chung J. N. Formation of bubbles in a simple co-flowing microchannel[J]. Journal of Micromechanics and Microengineering, 2007, 17(5): 1002-1011.

[16] Fuerstman M. J., Lai A., Thurlow M. E., et al. The pressure drop along rectangular microchannels containing bubbles[ J] Lab on a Chip, 2007, 7(11): 1479-1489.