An energy-based model for electrowetting-induced droplet actuation

Electrowetting (EW) induced droplet motion has been explored in the past decade in view of its promising applications in the field of microfluidics. This paper demonstrates the potential of energy-based analyses for modeling the performance of EW-based fluid actuation systems. Analyses based on system energy minimization offer simplified modeling tools to predict the overall performance of EW systems while circumventing the need to model the numerous complexities in the system. An analytical model is developed to estimate the actuation force on a droplet moving between two electrodes. The origins and contributions of various components of the actuation force are analyzed. The effects of dielectric parameters, electrode layout, droplet geometry and shape are discussed with the objective of maximizing the actuation force. The actuation force model is combined with semi-analytical models for predicting the forces opposing droplet motion to develop a model that predicts transient EW-induced droplet motion. Parametric results are obtained to evaluate the importance of operating voltage, fluid properties and droplet geometry on droplet motion.