Inkjet-Printed Split Ring Resonators for Microwave Sensor Applications on Flexible Kapton Substrate

The focus of this work is to demonstrate the functionality of sensors based on inkjet-printed split-ring resonators (SRR), which can be used for various applications, especially for the future development of patient-oriented diagnostics. An electromagnetic wave in the microwave range is coupled into the inkjet-printed gold split-ring resonator via a copper-printed stripline. The resonant frequency, which depends on the resonator geometry and material parameters, is then measured. The sensing functionality of the SRR is demonstrated by measuring the resonant frequency shift for three different liquid droplets applied to the sensor surface (ethanol, distilled (DI) water and dimethyl sulfoxide (DMSO)). A key advantage of this type of resonator is that it can be printed directly onto a substrate, saving resources and materials. In addition, an insertion system allows the printed sensors to be changed quickly, resulting in fast measurements.