Symmetric LC Circuit Configurations for Passive Wireless Multifunctional Sensors

A passive inductor-capacitor (LC) wireless sensor is capable of continuous real-time detection in applications that require the sensor to be powered remotely and to occupy a small volume, such as harsh and sealed environments, where physical access is difficult. However, the previously reported sensor can only monitor one single parameter of interest at a time. Here, we report a symmetric LC topological circuit configuration that consists of two LC resonators and show that it can be used to monitor double parameters simultaneously. The symmetric LC configuration separates the resonant frequency of the two different LC resonators at the circuit networks from each other. We demonstrate the use of this configuration to detect both pressure and humidity. In our prototypes, the Polydimethylsiloxane elastomer with pyramidal microstructures was utilized to fabricate the pressure sensor, and graphene oxide was utilized to fabricate the humidity sensor. Experiments demonstrate that the sensitivity of the pressure sensor is -48.5 kHz/mmHg and the sensitivity of the humidity sensor is -67.7 kHz/% RH, showing that the sensors are independently response to pressure or humidity. Overall, this symmetric LC topological circuit configuration that consists of multiple LC resonators represents a versatile approach for multiple parameters monitoring.