3D-printed split ring resonators as potential microwave strain sensors

In the current study, mm-scale, split ring resonator meta-atoms are tested as potential strain sensors. In particular highly flexible, stand-alone split ring resonators were developed employing the so-called stereolithography technique, and subsequently coated with conductive silver paste, to achieve high electrical conductivity. All of them, exhibit sizable resonance features in the frequency regime 3–8 GHz, depending on their dimensionality. In order to study their electromagnetic response upon strain deformations, meta-atoms were attached on highly flexible stripes, made of acrylic joint sealant. In all cases, a clear shift of the linear electromagnetic response was recorded, upon strain induced (up to 40%), enabling their sensing capability. Such experimental results were further confirmed by corresponding theoretical simulations. The performance of such strain sensors was evaluated through strain sensitivity and strain gauge factor, reaching up to 6.1 MHz/%, and 0.144 respectively. On the other hand, the electromagnetic performance of the SRRs, in the presence of strain, was verified through the quality factor, laying in the range 40–50, while the measurement error was found to be 2.3–14%, depending on the sample. Moreover, all resonators exhibited high durability in fatigue experiments, as well as they did not show any hysteretic behavior, upon a full stress-destress cycle. Thus, 3D—printed split ring resonator metasurfaces emerge as potential candidates for strain sensing applications.