An electromechanical model of an electro-responsive liquid droplet actuator for microsystems: Modeling and verification

Abstract

Dielectric liquids are used to actuate microfluidic devices. Droplet movement is achieved by applying a voltage across the electrodes beneath the dielectric substrate material. To understand the dynamics of these systems, an electromechanical model of a dielectric liquid movement between two parallel plate electrodes is presented herein. The system was modeled using lumped parameter approach using an equivalent capacitance circuit. This model was used to calculate the net electrostatic force acting on the liquid droplet and to predict the response of the liquid under the step input voltage. This model could be generalized to estimate the response of the any dielectric liquids in microfluidic devices of known geometry. Further, it could be used to design any model-based controller to accurately control actuating liquid for displacement or force control applications. The experiments were conducted with the water droplet as a dielectric liquid to validate the theoretical model and to analyze its dynamic characteristics under applied DC voltage. We experimentally investigated the effect of applied voltage, gap between the parallel electrodes, relative permittivity of dielectric fluid, and thickness of substrate material on the response of the water droplet.