Modeling, Simulation, and Optimization of Electrowetting

Electrowetting is an elegant method to realize the motion, dispensing, splitting, and mixing of single droplets in a microfluidic system without the need for any mechanical—and fault-prone—components. By only applying an electric voltage, the interfacial energy of the fluid–solid interface is altered and the contact line of the droplet is changed. However, since the droplet shape is usually heavily distorted, it is difficult to estimate the droplet shape during the process. Further, it is often necessary to know if a process, e.g., droplet splitting on a given geometry, is possible at all, and what can be done to increase the system´s reliability. It is thus important to use computer simulations to gain an understanding about the behavior of a droplet for a given electrode geometry and voltage curve. Special care must be exercised when considering surface-tension effects. We present computer simulations done with the Surface Evolver program and a template library combined with a graphical user interface (GUI) that facilitates standard tasks in the simulation of electrowetting arrays.