Electrode-gel-skin interface characterization and modeling for surface biopotential recording: Impedance measurements and noise

In this work, electrical impedance spectroscopy (EIS) has been used to characterize the electrical properties of the electrode-electrolyte interface and the electrode-skin interface. The impedance was measured from face to face Ag/AgCl electrode pairs, as well as the impedance of Ag/AgCl electrodes placed on the human body surface, in the frequency band from 0.05Hz to 1MHz. The obtained frequency responses of each interface were analyzed to determine their electrical models, with parameterization of the described impedance models using an optimization program written in Matlab source software. The thermal noises were also calculated for both interfaces.