Microwave Wearable System for Sensing Skin Hydration

In spite of the technological advancement of the healthcare system, monitoring skin hydration still remains a challenging task. The solutions currently available in the literature are inadequate to obtain continuous real-monitoring, especially in a wearable perspective. Starting from these considerations, this paper addresses the implementation of an innovative wearable device that can monitor skin hydration through microwave reflectometry technique. In particular, a preliminary validation was carried out through time-domain reflectometry (TDR) in-vivo measurements, from which the corresponding frequency-domain (FD) data were extrapolated. Successively, an in-depth study on the frequency response of the sensing element designed with respect to different skin hydration levels was carried out through full-wave simulations on human phantoms. This strategy allowed to consider different reference skin hydration levels and to obtain specific calibration curves relating the dielectric permittivity of skin to the FD-response of the monitoring system. The obtained results have thus led to the implementation of a system based on microwave reflectometry, with large potential for real-time, continuous monitoring of skin hydration.