Impedance spectroscopy and electrical modeling of electrowetting on dielectric devices

Using impedance spectroscopy, we have determined models for the elements which determine the ac electrical behavior in electrowetting on dielectric (EWOD) systems. Three commonly used EWOD electrode configurations were analyzed. In each case, the impedance can be modeled by a combination of elements, including the solution resistance, the capacitance of the dielectric layer, and the constant phase impedance of the electrode double layers. The sensitivity of the system's impedance to variations in the electrowetted area is also analyzed for these common configurations. We also demonstrate that the impedance per unit area of typical EWOD systems is invariant to bias voltage.