Impedance Characterization and Modeling of Electrodes for Biomedical Applications

TLDR

Low electrode‑electrolyte impedance is essential for biomedical electrodes, requiring a comprehensive understanding of the physical processes that contribute to impedance. The study aims to validate and extend a model of these processes to quantify how organic coatings and incubation time affect electrode impedance. Electrochemical impedance spectroscopy was performed on platinum, platinum black, and titanium nitride electrodes of various sizes, and the data were fitted to an equivalent circuit comprising an interface capacitance shunted by a charge‑transfer resistance in series with solution resistance, enabling quantification of coating and incubation effects. The fitted parameters matched theoretical calculations of interface capacitance impedance and solution resistance, confirming the model’s validity and demonstrating its utility for understanding complex biomedical interface phenomena.

Abstract

A low electrode-electrolyte impedance interface is critical in the design of electrodes for biomedical applications. To design low-impedance interfaces a complete understanding of the physical processes contributing to the impedance is required. In this work a model describing these physical processes is validated and extended to quantify the effect of organic coatings and incubation time. Electrochemical impedance spectroscopy has been used to electrically characterize the interface for various electrode materials: platinum, platinum black, and titanium nitride; and varying electrode sizes: 1 cm/sup 2/, and 900 /spl mu/m/sup 2/. An equivalent circuit model comprising an interface capacitance, shunted by a charge transfer resistance, in series with the solution resistance has been fitted to the experimental results. Theoretical equations have been used to calculate the interface capacitance impedance and the solution resistance, yielding results that correspond well with the fitted parameter values, thereby confirming the validity of the equations. The effect of incubation time, and two organic cell-adhesion promoting coatings, poly-L-lysine and laminin, on the interface impedance has been quantified using the model. This demonstrates the benefits of using this model in developing a better understanding of the physical processes occurring at the interface in more complex, biomedically relevant situations.