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A diffuse-interface model for electrowetting drops in a Hele-Shaw cell

Published online by Cambridge University Press:  15 October 2007

H.-W. LU ,
K. GLASNER ,
A. L. BERTOZZI  and
C.-J. KIM
H.-W. LU
Affiliation:
Department of Mechanical and Aerospace Engineering, UCLA, Los Angeles, CA 90095, USA
K. GLASNER
Affiliation:
Department of Mathematics, University of Arizona, Tucson, AZ 85721, USA
A. L. BERTOZZI
Affiliation:
Department of Mathematics, UCLA, Los Angeles, CA 90095, USA
C.-J. KIM
Affiliation:
Department of Mechanical and Aerospace Engineering, UCLA, Los Angeles, CA 90095, USA
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Abstract

Electrowetting has recently been explored as a mechanism for moving small amounts of fluids in confined spaces. We propose a diffuse-interface model for drop motion, due to electrowetting, in a Hele-Shaw geometry. In the limit of small interface thickness, asymptotic analysis shows that the model is equivalent to Hele-Shaw flow with a voltage-modified Young–Laplace boundary condition on the free surface. We show that details of the contact angle significantly affect the time scale of motion in the model. We measure receding and advancing contact angles in the experiments and derive their influence through a reduced-order model. These measurements suggest a range of time scales in the Hele-Shaw model which include those observed in the experiment. The shape dynamics and topology changes in the model agree well with the experiment, down to the length scale of the diffuse-interface thickness.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 590 , 10 November 2007 , pp. 411 - 435
Copyright
Copyright © Cambridge University Press 2007

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