Bioimpedance Measurement: Modeling of Coplanar Electrodes and Impedance Characterization

In many bioimpedance measurements, coplanar electrodes have to be used because the conventional parallel-plate configuration is either impossible or not preferred. Despite the widely use, the effect of the electrode geometry on the measurement, and the physical process of electrode-electrolyte interface impedance have not been well studied. In this work, we designed a type of fingers-like coplanar electrode and described the impedane measurement method for different test objects, which included various biologically relevant solution, blood and excised tissue. For best understanding interface characteristics of those objects, we adopted electrochemical impedance models to analyze the physical processes, and compared the electrical properties of these objects by amptitude-frequency plots in the frequency range of 100 Hz to 10 MHz. The results show that the impedance measurement method is effective, and fingers-like coplanar electrode can be used for bioimpedance measurement.