Non-destructive volume and thickness measurements with planar microwave sensors

This paper reports on the development of novel microwave sensors for non-destructive volume and thickness measurements in real-time. The sensors are in the form of metal patterns printed on planar substrates, and the type of both the metal and the substrate used alters the sensitivity of the sensor. In particular, changes in the response of these sensors in the microwave region of the electromagnetic spectrum when in contact with deionised water of 10-350 μl volumes and polyvinyl cellulose in 0.15-0.60 mm thicknesses are used as an indicator of volume/thickness respectively. Resonant peaks change their frequency and amplitude depending on the type and amount of material brought in contact with the sensor. This method offers increased sensitivity, real-time response and non-destructive evaluation of material type and profile, which can be used for structural health monitoring, for concealed target detection and security, and in a range of biomedical applications.