Comparison of Detection Error in Depth-Profiling Between Selective-Passivation and Incremental Compensation for Electrical Impedance Spectroscopy on a Needle

ENN (electrical impedance spectroscopy on-a-needle with non-passivation) can be used to discriminate bio-tissues based on depth-profiling. Since the ENN electrodes are comprised of a detection and connection parts, electrical impedance on the connection part tends to cause a distortion in the sensor output depending on the penetration depth. This distortion leads to an inaccurate evaluation of the electrical properties (conductivity and permittivity). In order to attenuate the distortion, two methods were proposed in previous studies as follows: ENS (electrical impedance spectroscopy on-a-needle with selective-passivation on the connection part) and ENNI (ENN with incremental compensation method). In this study, we compared the detection error between the two proposed methods in terms of the depth-profiling for three-layered porcine tissues. To evaluate the detection error of the aforementioned methods, the electrical properties obtained by the two methods were compared against reference values obtained directly from the side of the tissues penetrating only detection part. In the case of ENS, the detection errors of conductivity and permittivity were 3.86 % and 3.25 %, respectively, while for ENNI, the detection errors were 10.50% and 4.57 %, respectively. Thus, despite involving a complicated fabrication process, ENS is expected to more useful than ENNI for the characterization of bio-tissues.