Measurement and Simulation of Conductive Dielectric Two-layer Materials with a Multiple Electrodes Sensor

Impedance spectroscopy has been shown to provide a great potential as a measuring technique for monitoring human blood glucose. The two major potential benefits are the ability to perform non-invasive and continuous measurements. Previous work has outlined the range of challenges of such an impedance based technique. Our impedance sensor is composed of several capacitive fringing field electrodes with various characteristic geometries to achieve the desired penetration depths in human skin and the underlying tissue. A comparison of the measurements made on reference materials of known dielectric properties with the results of electromagnetic field simulations allows sensor characterization to be achieved and provides the ability to optimize the sensor geometry. Such comparisons reveal that the measurements and simulations are in qualitative agreement with the expected impedance behavior, i.e. there is a larger sensitivity to changes in the dielectric properties of the deeper layer for electrodes with a deeper penetration of the electromagnetic field (EMF). Another conclusion is that, despite the approximations made in the simulation process, the measured and simulated quantities agree. This opens the possibility to use simulations to define the functional relation between the measured impedances and the layers' dielectric parameters in order to correlate impedance changes with glucose concentration changes.