A wireless slot-antenna integrated temperature-pressure-humidity sensor loaded with CSRR for harsh-environment applications

In this study, a wireless slot-antenna integrated temperature-pressure-humidity (TPH) sensor loaded with complementary split ring resonator (CSRR) for harsh-environment applications was presented. The sensor is a multi-resonance structure with three separate resonant frequencies, which renders simultaneous measurements of temperature, pressure and humidity by placing sensitive elements in the corresponding CSRR structures. The sensitivity mechanisms for the temperature, pressure and humidity sensing are described in detail. The sensor was customized and fabricated on the high temperature co-fired ceramics (HTCC) using the three-dimensional co-firing and screen-printing technology. The humidity-sensitive graphene oxide modified polyimide (GO@PI) was used and characterized by the scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). The as-prepared TPH sensor can stably work at the ambient environment of 25–300 ℃, 10–300 kPa, and 20–90 %RH. The temperature sensitivity of the TPH sensor is 133 kHz/℃. The frequency shift of the pressure sensor is 30 MHz with a highest sensitivity of 107.78 kHz/kPa at 60 %RH, and 300℃. The humidity sensor realizes a sensitivity of 389 kHz/%RH in the low humidity of 20–60 %RH and 1.52 MHz/%RH in the high humidity of 60–90 %RH at 10 kPa, and 25 ℃. The sensor described in this study has the advantages of simple structure, higher sensitivity, and lower environmental interference and has the potential for utilization in simultaneous TPH monitoring in harsh environments.