Wearable sensor for in-vivo skin hydration monitoring

Skin hydration is the water content within skin tissues and its monitoring is of crucial importance in many contexts. However, at the current state-of-the-art, there is a lack of objective, non-invasive and wearable monitoring systems for the correct evaluation of skin moisture. To this purpose, in this paper, a new wearable punctual sensing element (SE) was designed and validated to sense variation of skin hydration of the body, even in the case of area as small as a few millimetres. In particular, a truncated customized open-ended coaxial probe was designed. As a matter of fact, the dielectric properties of the skin can be related to the frequency domain (FD) response of the monitoring system. In this regard, full-wave simulations on human phantoms were carried out to demonstrate the feasibility of the system. This strategy, in combination with low-cost miniaturized instrumentation, has potential for achieving a fully wearable system for real-time monitoring of skin hydration.