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Issue 1, 2015
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Velocimetry in microchannels using photobleached molecular tracers: a tool to discriminate solvent velocity in flows of suspensions

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Abstract

We report the development and analysis of a velocimetry technique based on the short time displacement of molecular tracers, tagged thanks to photobleaching. We use confocal microscopy to achieve a good resolution transverse to the observation field in the direction of the velocity gradient. The intensity profiles are fitted by an approximate analytical model which accounts for hydrodynamic dispersion, and allow access to the local velocity. The method is validated using pressure driven flow in microfluidic slits having a thickness of a few tens of micrometers. We discuss the main drawbacks of this technique which is an overestimation of the velocity close to the walls due to the combination of molecular diffusion and shear. We demonstrate that this error, limited to a near wall region of a few micrometers thick, could be controlled by limiting the diffusion of fluorophore molecules or minimizing the bleaching time. The presented technique could be combined with standard particle imaging velocimetry to access velocity differences and allow particle trajectory analysis in microflows of suspensions.

Graphical abstract: Velocimetry in microchannels using photobleached molecular tracers: a tool to discriminate solvent velocity in flows of suspensions

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Publication details

The article was received on 12 Sep 2014, accepted on 22 Oct 2014 and first published on 23 Oct 2014


Article type: Paper
DOI: 10.1039/C4SM02049A
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Soft Matter, 2015,11, 169-178

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    Velocimetry in microchannels using photobleached molecular tracers: a tool to discriminate solvent velocity in flows of suspensions

    F. Schembri, H. Bodiguel and A. Colin, Soft Matter, 2015, 11, 169
    DOI: 10.1039/C4SM02049A

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