Electrowetting and electrowetting-on-dielectric for microscale liquid handling

This paper deals with electrowetting (EW) and electrowetting-on-dielectric (EWOD) principles applied to microfluidic devices. EW and EWOD are principles that can control wettability of liquids on solid surfaces using electric potential. While EW is controlling wettability of a certain electrolyte on a metal electrode by varying electric energy across the electrical double layer (EDL), EWOD applies to virtually any aqueous liquid by varying electric energy across the thin dielectric film between the liquid and conducting substrate. These driving mechanisms have many advantages. By electrically changing the wettability of each of the electrode patterns on a surface, a liquid on these electrodes can be shaped and driven along the active electrodes, making microfluidics extremely simple both for device fabrication and operation, It is also worth noting that, driven by surface tension, the mechanism becomes more effective as the size of the device becomes smaller. This paper describes fundamental concepts and the proof-of-concept experiments, modeling and design, microfabrication processes, and initial testing results for the microfluidic devices based on the EW and EWOD principles. (C) 2002 Elsevier Science B.V. All rights reserved.