Numerical Simulation of Digital Microfluidics Based on Electro-Dynamic Model

Aiming at the doubt and divarication about the internal mechanism of electrowetting on dielectric (EWOD) in digital microfluidics, the authors attempted to explain the internal mechanism of EWOD through electrodynamic-based numerical simulation model. First, the boundary conditions for the governing equation were found. Then the influence of mesh number on simulation results was analyzed and feasibility of the simulation model was verified by comparing numerical results with theoretical ratiocination. Finally, they compared the electro-dynamic actuation force acting on the surface of droplet on three digital microfluidic structures, which have the same three-phase contact line but different area of contact domain. Analytical results showed that electro-dynamic force generated solely by the accumulation of induced charges in contact domain was three times larger than that generated by three-phase contact line. Induced charges accumulated on both three-phase contact line and contact area of droplet gave the contribution to EWOD, but contact area played a major role in the change of contact angle of droplet. DOI: 10.4018/ijimr.2012070102 International Journal of Intelligent Mechatronics and Robotics, 2(3), 14-23, July-September 2012 15 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. so on, has drawn extensive attention in almost all countries. EWOD can be defined as the changes of contact angle of liquid droplets at three-phase contact line through an external applied voltage. The mathematical relation between contact angle and the applied voltage satisfies the Young-Lippmann equation as follows (Choet al., 2003; Lee et al., 2002; Moon et al., 2002; Mugele & Baret, 2005; Vallet & Berge, 1999): cos cos θ θ ε ε γ = +