Spatially extended FCS for visualizing and quantifying high-speed multiphase flows in microchannels

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Original entry: Caspar Floryan, APPHY 225, Fall 2010

Reference

Spatially extended FCS for visualizing and quantifying high-speed multiphase flows in microchannels S.M. Hashmi, M. Loewenberg and E.R. Dufresne, Optics Express, 15 6528 (2007)

Keywords

Microfluidic, Flow, Kymograph, Imaging, Fluorescence, Auto-correlation, Velocity

Summary

This article describes a method for measuring the flow velocity inside multi-phase microfluidic channels using using fluorescence imaging. Multiphase microfluidics, such as droplet microfluidics, has expanded into an important field. This paper surmises that it would be useful to understand the properties of flows inside such channels.


A sample microfluidic channel with an approximate depth of 20 microns and a width of 50-75 microns was placed under a confocal microscope. Fluorescently-labeled particles were then flowed through the channels. The flow was recorded using a high speed camera. A diagram of the experimental setup is shown below in figure 1:

Caspar Summary7 Pic1.JPG


The resulting frames were stacked together into a kymograph. A kymograph is a graphical representation of spatial position over time, where one axis represents time. The kymograph's gray levels were inverted to make the particles stand out in front of a black background. This is shown below in figure 2:

Caspar Summary7 Pic2.JPG


Finally the authors calculated the auto-correlation of the kymograph to give the flow velocity of the particles. This method works for flows of up to 1cm/s.

Caspar Summary7 Pic3.JPG