Interpretation of Platinum Microelectrodes Impedance Response Using Measurement Model

Microelectrodes are used for cellular and neurophysiological applications. This study is focused on identifying the electrical properties of platinum electrodes using electrochemical impedance spectroscopy. Impedance spectroscopy is a powerful tool to study the non-ideal electrical circuits by considering frequency-dependent potential as input and frequency-dependent current as output. The impedance data can be fitted by a process model to predict the material and transport properties of a system.

The impedance data was collected with the Gamry Reference 3000 Potentiostat at three potentials: open circuit (OC), OC+10mV, and OC-10mV. A sinusoidal perturbation of 25 rms was applied for a frequency range of 1MHz to 0.1Hz. The electrolyte was phosphate-buffered saline, and the working electrode was connected to a platinum-mesh counter electrode and a silver/silver chloride (Ag/AgCl) reference to form a 3-electrode cell configuration. The measurements were taken under aerated conditions and controlled at a temperature of 37ºC.

The measurement model program by Watson and Orazem [1] was used to analyze impedance data. The program fits the Voigt element series to impedance spectra within the 95.4 % confidence interval. The stability and causality of the impedance response were inspected by analyzing the stochastic error structure. The linearity was confirmed by studying Lissajous plots. The process model indicated that the electrochemical system included reduction of oxygen, which was influenced by diffusion, oxidation of water, and the constant-phase-element behavior of the electrode.

Acknowledgements:

The authors thank Prof. Won Tae Choi and his student Seokjun Han for providing the electrodes used in this study.

References:

[1] W. Watson and M. E. Orazem, EIS: Measurement Model Program, Version 1.8, ECSArXiv, 2023, 10.1149/osf.io/g2fjm.”