Modeling and Simulating the Fluid Dynamics of Electrowetting On Dielectric (EWOD)
by: Shawn Walker


Electrowetting On Dielectric (EWOD) refers to a parallel-plate device that
moves fluid droplets through electrically actuated surface tension effects.
The fluid dynamics are modeled using HeleShaw type equations (in 2-D) with a
focus on including the relevant boundary phenomena. Specifically, we model
contact line pinning as an inequality constraint for the motion of the
liquid-gas interface that accounts for the "sticking" effect of the
interface.  The model is presented in a variational framework and is
discretized using Finite Elements.  The curvature/surface tension is
discretized in a semi-implicit way for accuracy using an explicit
representation of the interface.  The line pinning effect is captured with a
variational inequality (similar in spirit to the Signorini problem).  In
addition to this, we are developing a method for handling pinching and
reconnection of droplet meshes in an automatic way.  Some simulations will
be presented exhibiting the pinning effect and some preliminary results on
topological changes.