Stretchable tunable frequency selective fabrics and their electromagnetic response mechanism

Tunable frequency selective surface (TFSS), whose resonant frequency can change with the external complex and changeable electromagnetic (EM) environments. In this study, using the composite thermoplastic polyurethane (TPU) film/spandex elastic fabric as the substrate, stretchable tunable frequency selective fabric (sTFSF) with excellent tensile resilience is prepared. When the sTFSF is stretched, the strain is linearly proportional to the resonant frequency, so the resonant frequency can be precisely regulated according to the strain. Due to the change in the size and shape of conductive units as well as the size of units, the equivalent inductance (L) and capacitance (C) of sTFSF can change during stretching, which can be used to tune the resonant frequency. The values of L and C are obtained by particle swarm optimization (PSO) algorithm, and the different widths of resonant peaks and the tuning mechanism of resonant frequencies are theoretically explained. Furthermore, the sTFSF exhibits good mechanical performance and durability. After 1000 stretching cycles, the tunable performance is basically unchanged. Overall, the sTFSF is a thin, flexible, and precisely tunable fabric with facile preparation process, which makes it an effective functional composite material with great application prospect.