Uncovering Molecular Mechanisms of Electrowetting and Saturation with Simulations

Jin Liu, Moran Wang, Shiyi Chen, and Mark O. Robbins

Phys. Rev. Lett. 108, 216101 – Published 21 May 2012

Abstract

Molecular dynamics simulations are used to explore the physical mechanisms of electrowetting and the limits of continuum theories. Nanoscale drops exhibit the same behavior seen in macroscopic experiments: The contact angle $θ$ follows continuum theory at low voltages and then saturates. Saturation limits applications of electrowetting and its origin is of great interest. In the simulations, saturation occurs when ions are pulled from the drop by large local fields. Saturation can be controlled by changing temperature, screening, or the energy binding ions to the fluid. We show a local force balance equation for $θ$ remains valid even after saturation and that the interface approaches the equilibrium contact angle within a few nanometers of the solid.

Received 9 October 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.216101

Authors & Affiliations

Jin Liu^1,*, Moran Wang^1,2, Shiyi Chen^1,3, and Mark O. Robbins^1,4,†

¹Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
²School of Aerospace and CNMM, Tsinghua University, Beijing 100084, China
³State Key Laboratory for Turbulence and Complex Systems and CAPT College of Engineering, Peking University, China
⁴Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA

^*Present address: School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, USA.
^†mr@jhu.edu