Substrate-integrated half-mode resonant near-field sensor for liquid characterization

A compact resonant near-field sensor is introduced for characterization of biological liquids. It is based on a folded substrate-integrated half-mode resonator with a planar sensing tip. Because of its planar geometry, a sample under test can be easily coupled to the sensor which, in turn, is potentially very low-cost. The sensitivity of the sensor on different aqueous solutions is tested experimentally at 5 GHz. Salt, sugar and ethanol solutions can be discriminated by the sensor with a change in concentration of less than 1 %. The device is suitable for system-in-package integration and may thus prove useful in biological and chemical applications.