Liquid droplet actuation and control on smooth and superhydrophobic surfaces using electric fields

This dissertation is targeted at the development of new approaches for enhanced electrical control of liquid droplets on smooth and superhydrophobic surfaces. Physics-based analytical and numerical models are presented to predict electrical actuation of an electrically insulating droplet between smooth flat plates. Extensive experimentation is carried out to benchmark a previously developed model which predicts the actuation force on a generic liquid droplet under actuation with AC voltages. The experiments quantify the dependence of the droplet velocity on the frequency of the AC voltage. These experiments span the entire spectrum of electromechanical actuation regimes, namely classical electrowetting, AC electrowetting and insulating liquid actuation. The dissertation also includes a systematic study of the heat transfer performance of droplet-based systems. Detailed experiments and modeling efforts are described which map out the heat dissipation capacity of discrete droplets. The heat transfer results presented in the dissertation form the basis for the development of novel droplet-based cooling schemes for microelectronics thermal management. The present work also studies the electrical actuation of droplets on superhydrophobic surfaces. One of the highlights of the work is the development of an electrical actuation scheme to induce the dewetting Wenzel-Cassie transition. Another key advancement is the development of double-roughness structured surfaces (in a single fabrication step) for enhanced superhydrophobicity