Self-powered optical-triboelectric sensor for remote vibration monitoring

Self-powered vibration sensors, particularly those utilising triboelectric nanogenerators (TENG), hold great promise for real-time monitoring of dynamic loads and structural health without external power sources. However, the electrical wiring required by this system can be vulnerable to electromagnetic interference and signal degradation over long distances due to the cable capacitance increasing proportionally with length. To address this challenge, we introduce a novel optical-triboelectric sensor that eliminates the need for a local power source and enables remote monitoring with minimal signal loss over long distances. This design integrates a TENG-based vibration sensor with an electrical-optical transducer, which contains a thin liquid crystal layer whose transm sandwiched between two electrodes. The alternating voltage generated by the triboelectric nanogenerator modulates the optical transmissivity of a thin liquid crystal layer within the transducer. Operating in reflection mode, the electrical-optical transducer detects changes in the optical transmissivity by measuring the intensity of the light that passes through the liquid crystal layer, reflects off a mirror at the opposite side, and returns through the layer. This reflected light intensity is directly proportional to the TENG's electrical voltage when the voltage across the liquid crystal layer is within its linear range (-2 V to 2 V). An external capacitor is connected in parallel to the TENG to regulate the voltage to within this range. The self-powered optical-triboelectric sensor can achieve a phase angle variation within 5.2° up to 1.0 kHz, a 3.0 dB bandwidth of around 2.8 kHz, and signal attenuation of 1.05 dB per km, which is significantly lower than the attenuation level of 11.73 dB for 60-meter coaxial electrical cable. Furthermore, the optical-triboelectric sensor system shows a considerably higher signal-to-noise ratio of 18.5 (at a distance of 1000 m) than the value of 3.21 at 60-meter electrical wiring. These results indicate that this self-powered optical-TENG sensor shows significant promise for remote load and structural health monitoring; it eliminates the need for a local power source at the sensor location and is immune to electromagnetic interference.