Embroidered rectangular split-ring resonators for material characterisation

In this paper, we report an embroidered rectangular split-ring resonator (SRR) operating at S band for sensing applications. We designed, fabricated and characterized the SRR sensor on a fabric that can conformally cover the surface of samples under investigation. The structure can be embroidered on any dielectric fabric at low cost using conventional embroidery methods. In addition, the method is suitable for the fabrication of large-scale arrays to cover large surfaces. We have demonstrated material characterization capability of the sensors using a specific design with a length of 60 mm and a width of 30 mm. We wrapped the sensors on low-density polyethylene (LDPE) bottles filled with deionized (DI) water and ethanol in our experiments and measured their resonant frequencies using a vector network analyzer (VNA). We measured the nominal resonant frequency of a specific sensor wrapped around an empty bottle as 2.06 GHz with a quality factor of 411. The shifts in resonant frequencies when the bottle was filled with ethanol and DI water are 42 MHz and 66 MHz, respectively.