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Article

Microfluidic Chamber Design for Controlled Droplet Expansion and Coalescence

1
Microfluidics Group, Institute for Photonic Technologies, IPHT-Jena, Albert-Einstein-Str. 9, 07745 Jena, Germany
2
Department of Physical Chemistry and Microreaction Technologies, Institute of Chemistry and Biotechnology, Technische Universität Ilmenau, Prof.-Schmidt-Straße 26, 98693 Ilmenau, Germany
*
Authors to whom correspondence should be addressed.
Micromachines 2020, 11(4), 394; https://doi.org/10.3390/mi11040394
Received: 12 March 2020 / Revised: 7 April 2020 / Accepted: 7 April 2020 / Published: 10 April 2020
(This article belongs to the Special Issue Microfluidic Devices for Biosensing)
The defined formation and expansion of droplets are essential operations for droplet-based screening assays. The volumetric expansion of droplets causes a dilution of the ingredients. Dilution is required for the generation of concentration graduation which is mandatory for many different assay protocols. Here, we describe the design of a microfluidic operation unit based on a bypassed chamber and its operation modes. The different operation modes enable the defined formation of sub-µL droplets on the one hand and the expansion of low nL to sub-µL droplets by controlled coalescence on the other. In this way the chamber acts as fluidic interface between two fluidic network parts dimensioned for different droplet volumes. Hence, channel confined droplets of about 30–40 nL from the first network part were expanded to cannel confined droplets of about 500 to about 2500 nL in the second network part. Four different operation modes were realized: (a) flow rate independent droplet formation in a self-controlled way caused by the bypassed chamber design, (b) single droplet expansion mode, (c) multiple droplet expansion mode, and (d) multiple droplet coalescence mode. The last mode was used for the automated coalescence of 12 droplets of about 40 nL volume to produce a highly ordered output sequence with individual droplet volumes of about 500 nL volume. The experimental investigation confirmed a high tolerance of the developed chamber against the variation of key parameters of the dispersed-phase like salt content, pH value and fluid viscosity. The presented fluidic chamber provides a solution for the problem of bridging different droplet volumes in a fluidic network. View Full-Text
Keywords: droplet microfluidics; segmented flow; channel confined; network interface; electrocoalescence; labdisc; self-controlled; compact disk CD-production; volume bridging; bypassed chamber droplet microfluidics; segmented flow; channel confined; network interface; electrocoalescence; labdisc; self-controlled; compact disk CD-production; volume bridging; bypassed chamber
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MDPI and ACS Style

Kielpinski, M.; Walther, O.; Cao, J.; Henkel, T.; Köhler, J.M.; Groß, G.A. Microfluidic Chamber Design for Controlled Droplet Expansion and Coalescence. Micromachines 2020, 11, 394. https://doi.org/10.3390/mi11040394

AMA Style

Kielpinski M, Walther O, Cao J, Henkel T, Köhler JM, Groß GA. Microfluidic Chamber Design for Controlled Droplet Expansion and Coalescence. Micromachines. 2020; 11(4):394. https://doi.org/10.3390/mi11040394

Chicago/Turabian Style

Kielpinski, Mark, Oliver Walther, Jialan Cao, Thomas Henkel, J. M. Köhler, and G. A. Groß 2020. "Microfluidic Chamber Design for Controlled Droplet Expansion and Coalescence" Micromachines 11, no. 4: 394. https://doi.org/10.3390/mi11040394

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