Energy minimization-based analysis of electrowetting for microelectronics cooling applications

Electrowetting-induced droplet motion between two flat plates has been explored in the past decade in view of its promising applications in the field of microfluidics. This paper analyzes EW-induced droplet motion in the absence of a top plate (one-plate configuration) and compares it to the two-plate configuration. An energy minimization framework is employed to predict the actuation force on a droplet in the one-plate configuration. This 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. The second part of the paper uses the energy minimization framework to develop a model to predict the contact angle of a static droplet on a rough surface subject to an EW voltage. The model is used to establish criteria to design rough surfaces for use in a hot-spot cooling application. The concept of an electrically tunable thermal resistance switch for hot-spot cooling applications is introduced and analyzed.