Modeling and Control of Electrically Actuated Surface Tension Driven Micro-Fluidic Systems

Electrowetting on dielectric (EWOD) micro-fluidic systems use electrodes to effectively locally change the surface tension properties of liquid droplets and to thereby move, split, merge, and mix liquids inside microscale devices. The system is aimed at creating a laboratory on a chip: a miniaturized device that can carry out all the tasks that are typically performed in a biochemistry laboratory. This paper describes our modeling and initial control results of EWOD systems. We show how applied voltages create a change in the equilibrium shape of liquid droplets, we present a fluid dynamic model of droplet motion, splitting, and merging that is appropriate for control design, we demonstrate an image sensing algorithm that finds the dynamic shape of the liquids in real time, and we describe a control algorithm that can steer individual particles inside liquid droplets and that can achieve precision splitting of liquid droplets. Our modeling results are verified using experimental EWOD data from UCLA, and our initial control results are verified using the models