A real-time self-powered wireless angle sensing system based on liquid dielectric capacitive angle sensor

As an essential component of bridge health monitoring system, angle sensor not only needs real-time wireless transmission capability and high environmental tolerance, but also faces problem such as high wiring costs for energy supply or difficult battery replacement. Here, a real-time self-powered wireless angle sensing system (SP-WASS) based on liquid dielectric capacitive angle sensor (LDCAS) was developed, which is mainly composed of a triboelectric nanogenerator (TENG), a gas discharge tube (GDT), and two series-connected LC resonant circuits. The GDT is introduced to achieve impedance matching between TENG and LC circuit of the transmitting terminal. The LDCAS is of a parallel-plate capacitor structure, and half-filled with different liquid dielectrics. LDCAS using 60 wt% ethanol solution as the liquid dielectric achieves a frequency sensitivity of 9.3 kHz/°, and enables stable operation from −20–40 °C. With the deflection angle increasing from 0 to 75°, the resonant frequency shifts from 3.2 to 3.9 MHz at −20 °C for the SP-WASS with LDCAS using 60 wt% ethanol solution as the liquid dielectric. And the SP-WASS achieves wireless transmission over 29.7 m with a peak-to-peak voltage of 2.24 V. This real-time SP-WASS offers a practical route for angle monitoring in actual working environments of the bridges.