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Dynamics of magnetic modulation of ferrofluid droplets for digital microfluidic applications

Sen, U; Chatterjee, S; Sen, S; Tiwari, MK; Mukhopadhyay, A; Ganguly, R; (2017) Dynamics of magnetic modulation of ferrofluid droplets for digital microfluidic applications. Journal of Magnetism and Magnetic Materials , 421 pp. 165-176. 10.1016/j.jmmm.2016.07.048. Green open access

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Abstract

Active control of droplet generation in a microfluidic platform attracts interest for development of digital microfluidic devices ranging from biosensors to micro-reactors to point-of-care diagnostic devices. The present paper characterizes, through an unsteady three-dimensional Volume of Fluid (VOF) simulation, the active control of ferrofluid droplet generation in a microfluidic T-junction in presence of a non-uniform magnetic field created by an external magnetic dipole. Two distinctly different positions of the dipole were considered – one upstream of the junction and one downstream. While keeping the ferrofluid flow rate fixed, a parametric variation of the continuous phase capillary number, dipole strength, and dipole position was carried out. Differences in the flow behaviour in terms of dripping or jetting and the droplet characteristics in terms of droplet formation time period and droplet size were studied. The existence of a threshold dipole strength, below which the magnetic force was not able to influence the flow behaviour, was identified. It was also observed that, for dipoles placed upstream of the junction, droplet formation was suppressed at some higher dipole strengths, and this value was found to increase with increasing capillary number. Droplet time period was also found to increase with increasing dipole strength, along with droplet size, i.e. an increase in droplet volume.

Type: Article
Title: Dynamics of magnetic modulation of ferrofluid droplets for digital microfluidic applications
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jmmm.2016.07.048
Publisher version: http://doi.org/10.1016/j.jmmm.2016.07.048
Language: English
Additional information: © 2016 Elsevier B.V. All rights reserved. This manuscript version is made available under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International license (CC BY-NC-ND 4.0). This license allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licenses are available at http://creativecommons.org/ licenses/by/4.0. Access may be initially restricted by the publisher.
Keywords: Digital Microfluidics; Ferrofluid; Magnetic Actuation; Microfluidic T-junction; Droplet Generation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1508249
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