AC impedance of the hydrogel-skin interface

An equivalent circuit model of the electrode-gel-skin interface impedance is described. It is shown that the circuit parameters have physical significance and that the study of their variations with time and electrodermal activity furnishes considerable insight into underlying physical processes. As hydrogels are hydrophillic, they adsorb excess moisture from the skin surface. Hydrogel based electrodes therefore have the ability to recover following bursts of electrodermal activity and are thus, it is suggested, well suited for use in psychophysiological studies.<>