Investigation of a semiconductor bioelectrode with Ohmic behavior in vivo: Impedance spectroscopy of p-type semiconductor electrodes in perfused living heart

In the majority of impedance spectroscopy experiments performed for characterization of the semiconductor∣electrolyte interface, mass transport effects produce a diffusional element in the impedance spectrum. We report here, results obtained in the heart that has been perfused for cardioplegia with Tyrode’s buffer. Electrodes employed include polypyrrole, polyaniline, poly(3-methylthiophene), and poly(3,4-ethylenedioxythiophene). he exception of a small, approximately constant – Im{Z} element (possibly related to the back junction), metallurgically perfect poly(3,4-ethylenedioxythiophene) electrodes exhibited Ohmic behavior. Such an electrode is important for sensing of biological signals since it does not suffer from the high-pass filtering traceable to charge accumulation at conductor surfaces, thus implying removal of Goüy–Chapman–Stern reactances.