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Numerical and theoretical analyses of the dynamics of droplets driven by electrowetting on dielectric in a Hele-Shaw cell

Published online by Cambridge University Press:  01 February 2018

Yasufumi Yamamoto Open the ORCID record for Yasufumi Yamamoto [Opens in a new window] ,
Takahiro Ito ,
Tatsuro Wakimoto  and
Kenji Katoh
Yasufumi Yamamoto*
Affiliation:
Department of Mechanical Engineering, Kansai University, 3-35, Yamate-cho 3-chome, Suita, Osaka, 564-8680, Japan
Takahiro Ito
Affiliation:
Department of Energy Engineering and Science, Nagoya University, Furo-cho Chikusa-ku, Nagoya, 464-8603, Japan
Tatsuro Wakimoto
Affiliation:
Department of Mechanical Engineering, Osaka City University, 3-3-138, Sumiyoshi-ku Sugimoto, Osaka, 558-8585, Japan
Kenji Katoh
Affiliation:
Department of Mechanical Engineering, Osaka City University, 3-3-138, Sumiyoshi-ku Sugimoto, Osaka, 558-8585, Japan
*
†Email address for correspondence: yamayasu@kansai-u.ac.jp
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Abstract

Droplet movement by electrowetting on dielectric (EWOD) in a Hele-Shaw cell is analysed theoretically and numerically. We propose a simple theoretical model for the motion, which describes well the voltage dependency of droplet speed below the saturation voltage as measured experimentally. The simulation method for numerical analyses is constructed by using the Young–Lippmann equation to represent EWOD and the generalised Navier boundary condition to represent the moving contact line in the context of the front-tracking method. With an adjusted slip parameter, the present full three-dimensional numerical simulation reproduces well the shape evolution and movement speed of droplets as observed experimentally. We verify the proposed theoretical model in numerical experiments with various shapes and voltages. Furthermore, we analyse theoretically the behaviour of the contact line at the onset of droplet motion as observed in the simulation and experiment, and we are able to estimate very well the time scale on which the contact angle changes.

JFM classification

Interfacial Flows (free surface): Capillary flows Drops and Bubbles: Drops Interfacial Flows (free surface): Contact lines
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 839 , 25 March 2018 , pp. 468 - 488
Copyright
© 2018 Cambridge University Press 

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