Vers une caractérisation sans contact de l'évolution des tissus organiques par des capteurs RF multifréquences

A non-contact dielectric characterization technique of organic tissues using high sensitivity multifrequency radio-frequency (RF) sensors has been developed. It is based on the use of new passive RF transmission line resonators (WMFR), whose original structure allows them to enter into resonance on a set of predetermined frequencies, and on the use of an instrumental system of remote control of the WMFR by multifrequency and multisensor inductive couplings. The WMFR resonators are used as inductive sensors able to transmit a magnetic field of various frequencies towards the organic medium to be characterized and, by reciprocity, to measure the variations of this induced field, which are related to the complex dielectric properties of the medium at the considered frequencies. Associated with a multi-frequency equivalent electrical model, the developed system allows to trace the changes of the complex properties of the investigated media on a given set of frequencies, and thus to produce a multi-scale analysis, spatially and/or over time. Experimental tests have validated the approach for the localization of local dielectric contrasts and the temporal evolution of organic media. This work opens the way to the development of non-invasive and low cost devices for 3D or 4D multiscale monitoring of organic tissues.