Integrated Triboelectric Energy Harvesting and Displacement Monitoring for Low-Frequency Railway Bridge Vibrations

Achieving sustainable structural health monitoring remains a critical challenge for intelligent railway infrastructures, where distributed sensing networks require continuous power supply and long-term maintenance. Although low-frequency railway bridge vibrations simultaneously contain harvestable mechanical energy and structural state information, existing systems generally exploit these functionalities independently, resulting in increased system complexity and limited energy utilization efficiency. Here, we present an integrated triboelectric vibration energy harvesting and displacement monitoring device (THM) for low-frequency railway bridge vibrations. By incorporating a quasi-zero-stiffness (QZS) mechanism, the energy harvesting unit achieves an enhanced low-frequency response, delivering an open-circuit voltage of 280 V, a short-circuit current of 28 μA, and a peak power of 9 mW. The device charges a 22 μF capacitor to 4 V within 45 s under 1.5 Hz excitation, demonstrating its capability to power low-power electronics. Simultaneously, a freestanding triboelectric sensing unit enables real-time girder–pier displacement monitoring, displacement-direction identification, and structural safety warning, exhibiting excellent linearity (R2 = 0.9886) and stable operation over 20,000 cycles. This work provides an integrated strategy for simultaneously harvesting energy and monitoring structural displacement from low-frequency railway bridge vibrations, offering a promising route toward self-sustained intelligent bridge health monitoring systems.