Toward an OFDM-Based Technique for Electrochemical Impedance Spectroscopy

Fibrosis represents an open issue for medium to long-term active implants given that this biological medium surrounds the stimulation electrodes and can impact or modify the performances of the system. For this reason, Embedded Impedance Spectroscopy techniques has been investigated these last years to sense the fibrosis. The following article introduces a new paradigm for Electrochemical Impedance Spectroscopy (EIS) derived from multi-carrier digital communication methods. Due to its properties of flat spectrum and fast generation the Orthogonal-Frequency Division Multiplexing (OFDM) technique for EIS seems to be a real alternative to traditional ones. This article focuses on this approach and defines its performances on gold electrodes used for in-vitro experiments. An embedded implementation is also presented. This designed prototype allows to measure a medium with an error between 2% and 3%, when stimulating with a 16 or 32 tones multitone signal and a sampling frequency of 12KHz.