Design, realization and test of a low-cost electrical impedance spectrocopy analyzer for biological samples

Electrical Impedance Spectroscopy is a technique widely used to characterize the impedance of a system over a range of frequencies by applying an electrical perturbation to it and measuring its response. Electrical Impedance Spectroscopy is mainly used to characterize materials (solid-state devices, batteries, etc) and in recent decades has also been used to characterize biological systems, such as human tissues, for medical applications. If the sample under test is a biological tissue the technique is called Bioelectric Impedance Spectroscopy: usually biological tissues are stimulated using a sinusoidal current signal, for safety reasons. In this research a low-cost Bioelectric Impedance Spectroscopy device was developed: a custom analog front end to apply the current signal and extract the electrical response of the sample was designed; a proof-of-concept prototype was realized to evaluate the preliminary performances of the system. The system was tested using the simplest equivalent circuit of a biological tissue that is a parallel between a resistance and a capacitance: the device is able to measure the magnitude of the sample impedance with a maximum relative error of about 10% and the phase of the sample impedance with a maximum relative error of about 4%.