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On the flow topology inside droplets moving in rectangular microchannels

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Title: On the flow topology inside droplets moving in rectangular microchannels
Authors: Ma, S
Sherwood, JM
Huck, WTS
Balabani, S
Item Type: Journal Article
Abstract: The flow topology in moving microdroplets has a significant impact on the behaviour of encapsulated objects and hence on applications of the technology. This study reports on a systematic investigation of the flow field inside droplets moving in a rectangular microchannel, by means of micro-particle image velocimetry (μPIV). Various water/oil (w/o) fluid mixtures were studied in order to elucidate the effects of a number of parameters such as capillary number (Ca), droplet geometry, viscosity ratio and interfacial tension. A distinct change in flow topology was observed at intermediate Ca ranging from 10−3 to 10−1, in surfactant-laden droplets, which was attributed primarily to the viscosity ratio of the two phases rather than the Marangoni effect expected in such systems. W/o droplet systems of lower inner-to-outer viscosity ratios tend to exhibit the well-known flow pattern characterised by a parabola-like profile in the droplet bulk-volume, surrounded by two counter rotating recirculation zones on either side of the droplet axis. As the viscosity ratio between the two phases is increased, the flow pattern becomes more uniform, exhibiting low velocities in the droplet bulk-volume and higher-reversed velocities along the w/o interface. The Ca and droplet geometry had no effect on the observed flow topology change. The study highlights the complex, three-dimensional (3D) nature of the flow inside droplets in rectangular microchannels and demonstrates the ability to control the droplet flow environment by adjusting the viscosity ratio between the two phases.
Issue Date: 22-Jul-2014
Date of Acceptance: 22-Jul-2014
URI: http://hdl.handle.net/10044/1/44129
DOI: http://dx.doi.org/10.1039/c4lc00671b
ISSN: 1473-0197
Publisher: Royal Society of Chemistry
Start Page: 3611
End Page: 3620
Journal / Book Title: Lab on a Chip
Volume: 14
Issue: 18
Copyright Statement: © 2014 Royal Society of Chemistry
Keywords: Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Biochemical Research Methods
Chemistry, Multidisciplinary
Nanoscience & Nanotechnology
Biochemistry & Molecular Biology
Chemistry
Science & Technology - Other Topics
BIOCHEMICAL RESEARCH METHODS
CHEMISTRY, MULTIDISCIPLINARY
NANOSCIENCE & NANOTECHNOLOGY
MICROFLUIDIC CHIP
IMAGE VELOCIMETRY
PIV
WATER
VISCOSITY
CELLS
VISUALIZATION
ENCAPSULATION
PLUGS
Capillary Action
Microfluidic Analytical Techniques
Rheology
Analytical Chemistry
03 Chemical Sciences
09 Engineering
Publication Status: Published
Appears in Collections:Bioengineering



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