Abstract
Electrode polarization (EP) happening due to accumulation of ions at the electrode/electrolyte interface is an inevitable phenomenon while measuring impedance spectrum in high conductivity buffers and at low RF spectrum. Well characterized time scales elucidating the EP effect are important for the rational design of microfluidic devices and impedance sensors. In this Article, interfacial impedance at the electrode/electrolyte interface is investigated considering channel height and Debye length effects on characteristic time scale in a binary electrolyte solution using parallel plate electrode configuration. Experimental results reveal self similarity of normalized electrical impedance as a function of the normalized frequency. The experimental results also match with numerical solutions obtained by finite element simulation of unsteady fully coupled Poisson-Nernst-Planck (PNP) equations. Furthermore, fractal shaped gold nanostructured electrodes are examined, and it has been proven that electric double layer (EDL) formed on porous electrode surfaces acts as a thick EDL and modifications to the characteristic time scale is necessary for porous electrodes. Finally, a constant phase element (CPE) model is proposed to account for the self-similar impedance spectrum, which can be used for different channel heights and solution conductivities..