Evaluation of a reflection based dehydration sensing method for wristwatch integration

This paper presents a compact dehydration measurement method, keeping in mind a system integration in a wristwatch housing. In contrast to the conventional measurement approach using two measurement antennas, the proposed measurement setup uses only one antenna and one metallic reflector. Measurements have been performed using a patch antenna immersed in a steel basin filled with a tissue-equivalent liquid. The microstrip antenna has been optimized for an application in the 2.45GHz ISM band and features a biocompatible passivation layer and a rigid aluminum housing. The tissue-equivalent liquid mimicks dielectric tissue properties over a hypotonic hydration change. The steel basin acts as a liquid retainer and as a metallic reflector for the measurement setup. Measurements with the proposed setup have shown, that a clear distinction of physiologically relevant hydration levels is possible.