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Frequency domain optical coherence tomography (OCT) with phase-resolved algorithm is presented to perform highresolution
(8 &mgr;m), cross-sectional imaging of structure and velocity in turbid gas-liquid slug flow inside a microtube and
turbid liquid-liquid flow inside chaotic mixromixers: a barrier embedded Kenics micromixer and a Kenics micromixer.
Slug flow, the most common flow regime in microfluidic gas-liquid two-phase flow, consists of trails of bubbles
separated by liquid slugs flowing concurrently and provides significant radial heat and mass transfer. Since interfacial
transports are proportional to the interfacial area between two phases, interfacial area concentration defined by
interfacial area per unit mixture volume is an important parameter in a biochip with turbid biofluids. All the en face
image techniques, such as light microscopy, experience errors in the interfacial area concentration measurement due to
light refraction. In addition, they have overlapping depth information from the layers within a laser sheet or a depth of
focus of the objective lens. OCT, however, can provide accurate interfacial area concentration in a microtube because it
is a cross-sectional imaging technique which dispenses with the refraction correction in the radial direction.
Simultaneously, OCT can measure bubble velocity and velocity field inside liquid slugs. The radial liquid velocity was
quantified without refraction correction. Two toroidal vortices per liquid slug were visualized which is the essential
mechanism for radial heat and mass transfers. The barrier embedded Kenics micromixer and Kenics micromixer are
high performance chaotic micromixers with complex three-dimensional geometry. Conventional techniques cannot
visualize a cross-sectional mixing pattern in such a complex micromixer. OCT, however, can image the pattern and,
thereby, show mixing mechanisms. The barrier embedded Kenics micromixer was proven to have a higher performance
by comparison mixing patterns of two micromixers.
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