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Optimization of the Van Der Pauw Method for Measuring the Electrical Properties Spectrum of Biological Solutions

Measuring the electrical properties of biological solutions is of great importance in biological studies and reveals many facts about the function of microscopic organisms. Four-electrode methods are commonly used to measure the electrical conductivity spectrum. In this study, an optimized bioimpedance sensor based on the Van Der Pauw’s (VDP) theory was proposed to measure the electrical conductivity of biological solutions at the frequency band of 50 kHz–2 MHz. For this purpose, by simulating the bioimpedance sensor in COMSOL software, the effect of various factors on measuring the electrical conductivity was investigated. Using the Nyquist curve, it was found that when the chamber diameter of the bioimpedance sensor is approximately selected three times the electrode diameter, the measurement error calculated by normalized root mean squared error (NRMSE) criterion would be less than 1%. Then, for the practical evaluation, the bioimpedance sensor with five different chamber diameters was constructed. The electrical conductivity spectrum of the saline solution with three different concentrations was measured using the bioimpedance sensors. The NRMSE criterion practically showed that if the electrode diameter be about one third of the chamber diameter, the measurement error would be less than 2%.