Note: Characterization of electrode materials for dielectric spectroscopy.

When measuring the dielectric properties of aqueous samples, the impedance of the electrode/sample interface can limit low frequency measurements. The electrode polarization problem can be reduced by increasing the effective surface area of the electrodes. In this work, impedance spectroscopy was used to characterize and compare three different electrode surfaces that can be used to mitigate this effect: platinum black, iridium oxide, and [polypyrrole/poly(styrenesulphonate)] (PPy/PSS) conducting polymer. All three materials were directly compared with a bright platinum electrode. Equivalent circuit models were used to extract the increase in the effective surface area of the electrodes: platinum black, iridium oxide and PPy/PSS increase the effective capacitance of the electrode by factors of approximately 240, 75, and 790, respectively. The practical aspects of all electrode materials are discussed. These results suggest that iridium oxide and PPy/PSS are good alternatives to the commonly used platinum black, which is prone to mechanical damage (scratches) and is potentially toxic to cells.

[1]  Andreas Hierlemann,et al.  Impedance characterization and modeling of electrodes for biomedical applications , 2005, IEEE Transactions on Biomedical Engineering.

[2]  V. Birss,et al.  Reversible ageing of iridium oxide electrodes in acidic solutions , 1993 .

[3]  U. Schnakenberg,et al.  Sputtered Iridium Oxide Films as Charge Injection Material for Functional Electrostimulation , 2004 .

[4]  L. Kappenberger,et al.  Acute and Long‐Term Ventricular Stimulation Thresholds with a New, Iridium Oxide‐Coated Electrode , 1993, Pacing and clinical electrophysiology : PACE.

[5]  David J. Anderson,et al.  Electrochemical deposition and characterization of conducting polymer polypyrrole/PSS on multichannel neural probes , 2001 .

[6]  James D. Weiland,et al.  In vitro electrical properties for iridium oxide versus titanium nitride stimulating electrodes , 2002, IEEE Transactions on Biomedical Engineering.

[7]  D. Georgiev,et al.  Amorphous and crystalline IrO2 thin films as potential stimulation electrode coatings , 2008 .

[8]  R Langer,et al.  Stimulation of neurite outgrowth using an electrically conducting polymer. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[9]  P. Vadgama,et al.  Impedimetric sensing of cells on polypyrrole-based conducting polymers. , 2007, Journal of biomedical materials research. Part A.

[10]  Yuliang Cao,et al.  Activated iridium oxide films fabricated by asymmetric pulses for electrical neural microstimulation and recording , 2008 .

[11]  M Carlà,et al.  An iridium-iridium oxide electrode for in vivo monitoring of blood pH changes. , 1981, Journal of medical engineering & technology.

[12]  S.F. Cogan,et al.  Electrodeposited iridium oxide for neural stimulation and recording electrodes , 2001, IEEE Transactions on Neural Systems and Rehabilitation Engineering.

[13]  Paul M. George,et al.  Fabrication and biocompatibility of polypyrrole implants suitable for neural prosthetics. , 2005, Biomaterials.

[14]  S. Gawad,et al.  Single cell dielectric spectroscopy , 2007 .

[15]  T Stieglitz,et al.  Characterization and optimization of microelectrode arrays for in vivo nerve signal recording and stimulation. , 1997, Biosensors & bioelectronics.

[16]  Microfluidic device to confine single cardiac myocytes in sub-nanoliter volumes for extracellular pH measurements , 2008 .

[17]  Yuri Feldman,et al.  Electrode polarization correction in time domain dielectric spectroscopy , 2001 .

[18]  H P Schwan,et al.  Alternating current electrode polarization , 1966, Biophysik.

[19]  Clifford D. Ferris,et al.  Four‐Electrode Null Techniques for Impedance Measurement with High Resolution , 1968 .

[20]  M. Tirado,et al.  Conductivity dependence of the polarization impedance spectra of platinum black electrodes in contact with aqueous NaCl electrolyte solutions , 2003 .