The Oscillation Dynamics of Droplets Subject to Electrowetting Actuation

The dynamic behavior of an electrowetting-on-dielectrics (EWOD) actuation process can be linked to certain fluid properties of the actuated polar liquid droplet. After actuation, inertia will lead to droplet oscillations, where the contact angle asymptotically approaches the newly created surface tension equilibrium value. The decay behavior, frequency, and amplitude of these oscillations can be related to material parameters, such as density, viscosity, and mass. In this paper, we study the characteristics of these oscillations, present simulation results, and develop a measurement setup for first observations of oscillations on deionized water droplets. We show that there is a big difference between two grounding schemes, in particular, regarding the dynamic movement of the liquid-gas interface. It turns out that only an electrical grounding from below leads to utilizable oscillations. Finally, we point towards applications for future Lab-on-a-Chip applications.