Preprint Article Version 1 This version is not peer-reviewed

Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization

Version 1 : Received: 16 October 2018 / Approved: 18 October 2018 / Online: 18 October 2018 (10:21:58 CEST)

A peer-reviewed article of this Preprint also exists.

Nitta, K.; Tsukahara, T. Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization. Micromachines 2018, 9, 533. Nitta, K.; Tsukahara, T. Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization. Micromachines 2018, 9, 533.

Journal reference: Micromachines 2018, 9, 533
DOI: 10.3390/mi9100533

Abstract

Liquid manipulation by photoisomerization attracts recent attentions as a new active droplet control method for micro-chemical analysis. Such a non-inverse manipulation can be realized by a use of solution liquid of surfactant that exhibits the \emph{cis}-\emph{trans} isomerization triggered by light irradiation with a specific wavelength such as ultraviolet light. Since the isomerization is accompanied by changes in fluid properties, a light irradiation on one of liquid-air interfaces of a liquid column in a tube would generate differences in the wettability accompanied between the both sides of the finite liquid column. Although this technique has been demonstrated experimentally by Muto et al. (\emph{Euro.~Phys.~J.~Special Topics}, {\bf 226}, 2016, 1199--1205), its dynamics and developments of each isomer distribution are not understood. In order to reveal the liquid-column migration phenomenon, we have performed numerical simulations of air-liquid two-phase flows and its scalar transport of the isomer, using the Volume-of-Fluid method in conjunction with the Continuum-Surface-Force model and Continuous-Species-Transfer method. We validated present results by comparison with experimental result in terms of the migration distance of the liquid column. We confirmed a termination of the liquid-column migration occurs when the \emph{cis} isomer distribution reaches the non-irradiated region. The migration speed was less dependent on the liquid-column length and was proportional to the tube diameter.

Subject Areas

computational fluid dynamics; contact line; droplet; lab-on-chip; liquid manipulation; microfluidics; non-invasive control; photochemical reaction; photoresponsible surfactant; two-phase flow; wettability

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