To obtain a performance
improved dry electrode for bioelectrical
activity detection is still a challenge, which is mainly due to the
poor fundamental understanding on the impedance of the electrode–skin
interface. Herein, the impedance between the electrode and the skin
interface of three types of electrodes, which are the wet electrode,
semidry electrode, and dry electrode, is investigated with electrochemical
impedance spectroscopy combined with the spectra fitting technique.
The parameters of performance duration, potential, and frequency associated
with the impedance are explored for these three types of electrodes.
The overall impedance is roughly constant within the performance duration
and the potential applied in this study. Along with the frequency
decreases, the impedance of the dry electrode reduces faster and is
more complicated compared with the other two types of electrodes.
Moreover, the results computed with the equivalent circuits show that
the charge transfer resistance is additionally present compared to
the wet and semidry electrodes. This large and additional charge transfer
resistance may explain its relatively poorer electrophysiological
properties.