Strain sensor based on a flexible frequency-selective surface with temperature compensation

In this Letter, a biaxial strain sensor based on a frequency-selective surface (FSS) is designed using a flexible polymer. The sensor achieves independent strain detection in the two-dimensional direction by biaxial mechanical deformation, and the resonant frequency shift is caused only by the mechanical deformation, which is insensitive to temperature changes. The FSS sensor was fabricated using photolithography, wet etching, and laser cutting techniques. In the heating test, the relative rate of change in the resonant frequency of the FSS sensor was 0.46% in the range of 20-100°C. In tensile tests, the FSS sensor showed a linear elastic relationship between stress and strain over a strain range of 0-66.6%. The sensitivity reached 700 MHz/mm when a tensile displacement of 0.5-3 mm was applied. The FSS sensors showed high strain sensitivity and resistance to temperature drift, which verified the practical value of the FSS sensors in complex environments.