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Microbubble lensing-induced photobleaching (μ-BLIP) with application to microflow visualization

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Abstract

The curvature of gas–liquid interfaces and the step change in properties across these interfaces in microchannels are shown here to create a powerful lens/mirror effect. In a hydrophilic system, light incident on the bubble is focused into the surrounding liquid, resulting in a locally increased total light exposure. The optical phenomena leading to this are discussed, and the effect is demonstrated experimentally by imaging the increased photobleaching rate of fluorophores in the near-bubble region. Numerical simulations of the system are performed to investigate the electrical potential and flow fields resulting from the application of an axial electric field. Microbubble lensing-induced photobleaching (μ-BLIP) is then applied as a method to inject a negative scalar flow marker for flow visualization in microchannels. Once formed, the electrokinetic transport of this marker is analyzed to determine the cross-channel velocity profile of the liquid phase and the liquid velocity in the film. Experimental data is verified by comparison with numerical predictions and previous experimental studies. This contribution represents both a new application of microscale gas–liquid interfacial phenomena, and a new technique for microfluidic flow visualization, particularly applicable (though not limited) to the study of multiphase microchannel flows.

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Acknowledgements

Financial support of this work by the Natural Sciences and Engineering Research Council (NSERC) of Canada, through post-graduate scholarships to D.S. and D.E. and a research grant to D.L., is gratefully acknowledged. Financial support from Glynn Williams, through a post-graduate scholarship to D.S. is also gratefully acknowledged.

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Authors and Affiliations

  1. Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto , Ontario, M5S 3G8, Canada

    D. Sinton, D. Erickson & D. Li

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  1. D. Sinton
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  2. D. Erickson
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  3. D. Li
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Correspondence to D. Li.

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Sinton, D., Erickson, D. & Li, D. Microbubble lensing-induced photobleaching (μ-BLIP) with application to microflow visualization. Exp Fluids 35, 178–187 (2003). https://doi.org/10.1007/s00348-003-0645-6

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  • DOI: https://doi.org/10.1007/s00348-003-0645-6

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