A self-powered triboelectric nanogenerator sensor for multiple bolts loosening detecting under impact loading

Bolted connections are widely used under impact loading conditions, and the detection of the bolts loosening is important. Although previous studies have utilized triboelectric nanogenerators (TENGs) for detecting bolt loosening, they have predominantly concentrated on the state of individual bolts. In this work, a self-powered Polyimide/Copper TENG (PC-TENG) sensor was proposed for the real-time monitoring of multiple bolts under impact loading. By incorporating LED indicators into each PC-TENG and measuring the output voltage, it is a simple and straight way to detect the presence of loose bolts and to identify their specific locations. Moreover, the possibility by only measuring the combined output voltages of TENG sensors was studied, and it was found that the TENG sensors with different output voltages were suitable for the multiple bolts detection, while the ones with similar output voltages cannot be employed for the multiple cases. The inconsistence of TENGs output results was often seen as a disadvantage, but in this work, we innovatively leveraged this behavior to enable multiple bolts loosening detection. By creatively utilizing distinct voltage outputs and integrated LED indicators, this PC-TENG system achieves simple, real-time identification of loose bolts in multi-bolt setups, offering a novel strategy for structural health monitoring in practical applications.