Issue 1, 2020

Microfluidics of binary liquid mixtures with temperature-dependent miscibility

Abstract

Liquid–liquid microfluidic systems rely on the intricate control over the fluid properties of either miscible or immiscible mixtures. Herein, we report on the use of partially miscible binary liquid mixtures that lend their microfluidic properties from a highly temperature-sensitive mixing and phase separation behaviour. For a blend composed of the thermotropic liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) and methanol, mixing at temperatures above the upper critical solution temperature (UCST; 24.4 °C) leads to a uniform single phase while partial mixing can be achieved at temperatures below the UCST. Thermally-driven phase separation inside the microfluidic channels results in the spontaneous formation of very regular phase arrangements, namely in droplets, plug, slug and annular flow. We map different flow regimes and relate findings to the role of interfacial tension and viscosity and their temperature dependence. Importantly, different flow regimes can be achieved at constant channel architecture and flow rate by varying the temperature of the blend. A consistent behaviour is observed for a binary liquid mixture with lower critical solution temperature, namely 2,6-lutidine and water. This temperature-responsive approach to microfluidics is an interesting candidate for multi-stage processes, selective extraction and sensing applications.

Graphical abstract: Microfluidics of binary liquid mixtures with temperature-dependent miscibility

Supplementary files

Article information

Article type
Paper
Submitted
20 sep 2019
Accepted
29 nov 2019
First published
02 dec 2019
This article is Open Access
Creative Commons BY license

Mol. Syst. Des. Eng., 2020,5, 358-365

Microfluidics of binary liquid mixtures with temperature-dependent miscibility

M. J. Fornerod, E. Amstad and S. Guldin, Mol. Syst. Des. Eng., 2020, 5, 358 DOI: 10.1039/C9ME00127A

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