Effect of uniaxial compression in the transmittance of a novel terahertz sensor for structural health monitoring

In this paper we present a study of a novel THz passive wireless micro-sensor that responds to uniaxial compressions. The sensor can work in two different modes of operation, namely, by variations of the resonance frequency or by variations of the intensity of the transmitted signals with respect to the applied compression. We develop a theoretical method to predict the transmittance and resonance frequency of the unit cells of the sensor. This method takes into account the rectangular shape of the wires in the structure, as well as the dispersion and losses. A numerical study is performed which demonstrates that, when the sensor works in the resonance frequency mode, its sensitivity is independent of the number of layers considered and has a value of 380 GHz/μm. In the intensity control mode, the sensor behaves in a non-linear manner and variations in the transmittance of the order of five to ten times are obtained when the sensor is compressed to 70% of its original size.