Impedance analysis of ZnO nanowire coated dry EEG electrodes

Abstract

The electrochemical impedance of a novel dry electroencephalogram (EEG) electrode after surface modification (i.e., sputtered with gold, coated with ZnO nanowires) is investigated in this study. To avoid the discomfort caused by repetitive testing on human, a skin-mimic sandwich structure, comprised of a highly porous polyester fabric membrane and two thin silicone films, is fabricated as a test bed. Electrochemical impedance spectroscopy (EIS) measurements are conducted to further understand the properties of the electrode-electrolyte interface when the electrode is installed on this test bed. An equivalent circuit model with a constant phase element (CPE) is used to fit the EIS data. Our results show that the modeled EIS data are in good agreement with the experimental data. It has also been found that the charge transfer resistance decreases from 349 Ω cm² for the bare electrode to 256 Ω cm² for the gold-coated electrode and further decreases to 167 Ω cm² for the gold coated short ZnO nanowire electrode. The lower impedance value will definitely help improve the signal when such electrode is used to record electrophysiological data.