Microwave split-ring resonators are utilized as sensors in a wide variety of applications due to their remarkable features, such as extremely low cost, high sensitivity, and relatively high quality factor. In this article, another application is enabled according to a recently demonstrated chipless tag-reader structure providing the possibility of simplifying the sensor structure from a “multilayer structure” consisting of a dielectric substrate sandwiched between two metallic layers to a single-layer structure formed from a conductive material. This capability is specifically important for strain sensing applications as it brings the possibility of utilizing low stiff conductive materials instead of copper (which is the primary material used in microwave application) while keeping the reader structure with high-quality microwave application-specified substrates intact. With the explained approach in this work, a low tensile silver-aluminum silicone elastomer conductive material is considered for the tag providing a very high tensile dynamic range. According to the whole sensing system structure, as high elongation range of as 20% and the high sensitivity in the range of 25 MHz/1% of strain is achieved. Multiple simulations and experimental results support the idea of the novel microwave strain sensor proposed in this work.
