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Published April 1, 2004 | public
Journal Article

Effects of viscosity on droplet formation and mixing in microfluidic channels

Abstract

This paper characterizes the conditions required to form nanoliter-sized droplets (plugs) of viscous aqueous reagents in flows of inuniscible carrier fluid within microfluidic channels. For both non-viscous (viscosity of 2.0 mPa s) and viscous (viscosity of 18 mPa s) aqueous solutions, plugs formed reliably in a flow of water-immiscible carrier fluid for Capillary number less than 0.01, although plugs were able to form at higher Capillary numbers at lower ratios of the aqueous phase flow rate to the flow rate of the carrier fluid (in all the experiments performed, the Reynolds number was less than 1). The paper also shows that combining viscous and non-viscous reagents can enhance mixing in droplets moving through straight microchannels by providing a nearly ideal initial distribution of reagents within each droplet. The study should facilitate the use of this droplet-based microfluidic platform for investigation of protein crystallization, kinetics, and assays.

Additional Information

Copyright © 2003 Elsevier. Received 4 August 2003. Revised 22 October 2003. Accepted 7 November 2003. Available online 8 January 2004. This work was supported by the Camille and Henry Dreyfus New Faculty Award, Chicago MRSEC funded by NSF, the ONR Young Investigator Award N00014-03-10482, the NIH (R01 EB001903), and by the Beckman Foundation. The work was performed at the Chicago MRSEC microfluidic facility. We thank H. Song and C.J. Gerdts for performing photolithography at MAL of UIC and for advice. We thank M.R. Bringer for helpful discussions.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023