Design and 3-D Printing-Assisted Fabrication of Microwave Resonator-Based Passive Wireless Sensors for Simultaneous Measuring High Temperatures and Pressures

Passive wireless sensors with the capability of mutliparameter measurement have valued industrial applications for monitoring mechanical structure operating parameters in harsh or high-temperature work environments. The passive wireless microwave sensors with a substrate-integrated waveguide (SIW) structure and a complementary split-ring resonator (CSRR) were designed and built to simultaneously detect temperatures and pressures. Incorporating CSRR into the SIW structure effectively enhances sensitivity of these CSRR-SIW sensors. Theoretical calculations and numerical simulations were conducted to optimize the sensor’s structural geometries and dimensions. The sensor was fabricated by a stereo lithography appearance (SLA)-based 3-D printing and laser-assisted selective electroless-plating (LA-SEP), which is highly efficient and scalable. Experimental results demonstrate that the resonant frequencies of the as-fabricated sensors closely matched the simulation results, with a deviation of less than 3.76% at room temperature. The CSRR-SIW sensor exhibits sensitivities of 125.219 kHz/°C and 121.575 kHz/kPa for temperature and pressure, respectively. We investigated and proposed a decoupling method to separate the coupled sensing signals of temperature and pressure for engineering applications. This method aims to enhance signal accuracy and reliability in practical scenarios.