Micro-Drops and Digital Microfluidics

4

Electrowetting Theory*

4.1 Introduction

In the presence of a direct or alternating-current electric field, electric charges gather at the interface between a conductive and a non-conductive (dielectric) material. The same electric field that induces these charges then couples with the interfacial electric charges to exert an interfacial force, and if the interface is deformable—like that of a conductive liquid and a non-conductive fluid or gas—this force can distort the interface. These induced interfacial electric forces are especially strong on a liquid–gas interface at the vicinity of the contact line, as the electric field often becomes singularly large at the sharp wedges near the contact line. The physics describing the electric forces ...