Development of a planar microwave resonator based wetness sensor

A planar microwave device suitable for use as a wetness sensor is presented in this article. The wetness sensor is a wirelessly addressable multi-frequency resonator designed on a flexible substrate. The resonator operating between 4.5 GHz to 8.5 GHz consists essentially of six cascaded open-ended transmission lines embedded within the central conductor of a coplanar waveguide. The presence or absence of fluid on the planar microwave resonator affects its resonance frequencies. Simulations and laboratory measurements show good results demonstrating the possibility of detecting wetness using the proposed method.