Bidirectional large strain monitoring using a novel graphene film-based patch antenna sensor

This study proposes a rectangular microstrip patch antenna sensor based on a high-conductivity graphene film for bidirectional strain detection in structural health monitoring (SHM). By using a highly conductive graphene film instead of traditional metal foil to produce a patch antenna, the antenna possesses a higher flexibility and a larger sensing range. The mechanical, electromagnetic, and radiative properties were investigated. The strain sensing principle based on the resonant frequency offset of the graphene film antenna was proposed. The relationships between the resonant frequency shift and structural strain were quantitatively explored through theoretical deductions, finite element simulations, and experiments. According to the experimental results, the shift in the resonant frequency was linearly related to the lateral and longitudinal strains. The sensitivity coefficients for the lateral and longitudinal strains were 2.2037 kHz/μϵ and 3.6198 kHz/μϵ, respectively. The thermal strain can be distinguished based on the linear resonant frequency-temperature relationship. The results demonstrated the advantages and prospects of the proposed novel patch antenna for SHM.