Modeling and Analysis for
Electrowetting Driven Hele-Shaw Flow with Contact Line Friction
Electrowetting On Dielectric (EWOD) refers to a parallel-plate device
that moves fluid droplets through electrically actuated surface tension
effects. These devices have potential applications in biomedical
`Lab-On-A-Chip' devices (automated DNA testing, cell separation) and
controlled micro-fluidic transport (e.g. mixing and concentration
control). The fluid dynamics are modeled using Hele-Shaw type
equations (in 2-D) with a focus on including the relevant boundary
phenomena. Specifically, we model contact line pinning as a static
(Coulombic) friction effect and effectively becomes 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.
Simulations are presented and compared to experimental videos of EWOD
driven droplets. These experiments exhibit droplet pinching and
merging events and are reasonably captured by our simulations.