Planar sensors for local conductivity measurements in biological objects—Design, modelling, sensitivity maps

The paper focuses on the realisation of the idea of local electrical conductivity measurement in biological objects. In particular, it presents a set of planar electrode sensors that can be used in such measurements. Properties and parameters essential for local conductivity measurements have been analysed and compared for proposed electrode arrangements. The analyses were performed using the Finite Elements Method. The correctness of the results obtained using this method was verified by comparison with the results obtained experimentally and calculated analytically. The influence of the sample volume and its environment conductivity on the measurement result has been analysed for the presented electrode configurations. These parameters determine which of the proposed sensors are preferable in local conductivity measurements and can help to increase credibility and repeatability of the result. The outcome of these analyses also determines requirements that have to be met to perform correct conductivity measurement. Alternatively, if these requirements cannot be met, at least the error of the measurement result can be estimated. Biological objects are usually heterogeneous so the knowledge of sensitivity maps of the sensor can be very useful. Therefore, the modelling procedure for sensitivity map calculations of any four-electrode planar conductivity sensor was proposed and described in this paper. This procedure has been used to calculate and present sensitivity maps of the sensors. The results of these calculations allow the sensitivity of the sensor for the selected area of the sample to be estimated and indicate which part of the measured object has the greatest influence on the measurement result.