Self-powered wireless sensing system is particularly suitable for applications in intelligent manufacturing, smart healthcare etc. as it does not require an external power source. Triboelectric nanogenerator (TENG) is an emerging energy harvester that can be used to power self-powered wireless sensors. The latest achievement in this area is the instantaneous self-powered wireless sensor, where the electric energy generated by the TENG is injected directly into the inductor-capacitor (LC) resonator to generate a decaying oscillating signal with encoded sensing information. However, the frequency is lower (typically < 5 MHz) and the signal transmission distance is short (< 3 m) limited by the near-field magnetic coupling, restricting its widespread applications. In this research, we propose a self-powered long-distance wireless sensing platform which utilizes a surface acoustic wave (SAW) resonator based radio-frequency oscillator to convert TENG energy into a high frequency signal with sensing information encoded. With this system, the sensing signal can be easily transmitted through the antenna for long distance. An optimized system is designed and conditional influences are fully investigated. Results show this self-powered wireless sensor system can perform wireless sensing for force, temperature and vibration at a distance up to 50 m.

Self-powered sensors are highly sought for wireless sensing applications in space exploration, industries, and environmental monitoring, etc. However, most current self-powered sensor technologies are based on the multiple energy conversion routine: energy collection, rectification, energy storage, and power management before it can be used for sensor systems, leading to exceptionally low energy utilization efficiency and very short periods of wireless sensing operation with majority of information lost. Here, we propose a triboelectric nanogenerator (TENG) based fully self-powered instantaneous and real-time wireless sensor system which does not contain electronic devices and microchips, but the passive components only. An innovative cylindrical capacitive-type liquid level sensor is also proposed and is then integrated into the wireless sensor system for monitoring liquid levels or identifying substance of the liquids. This sensor system can convert pulsed voltage output of the TENG into sinusoidal signal with a resonant frequency containing the sensing information and is transmitted to the receiver in distance in real-time. The maximum transmission distance of the sensor system could reach 1.5 m for a 10 cm diameter magnetic-core coil pair. The wireless sensor system exhibited excellent stability and excellent linearity with a sensitivity of 4.63 kHz/cm, and demonstrated its great application potential for the self-powered liquid level monitoring.