Self-powered retractable reel sensor for crack monitoring and warning in civil infrastructures

Crack occurrence and propagation are among the critical factors that affect the performance and lifespan of civil infrastructure such as bridges, buildings, etc. Therefore, numerous crack detection and characterization techniques have been developed over the past decades. In this study, we proposed the self-powered with the merits of cost-affordable, high resolution, and wide monitoring range to monitor small cracks in infrastructure. The selfpowered retractable reel sensor includes two triboelectric nanogenerator (TENG) sensing units for low and high speed fracture monitoring, respectively. By using the principle of retractable reel structure, the linear motion of the crack is converted into the rotation of the TENG. Through peak extraction and pulse counting, the testing of crack velocity and displacement was realized simultaneously. A real resolution of 0.222 mm are achieved through the structural design and electrical performance characterization. With the help of the LabVIEW platform and multi-channel data acquisition program, its application in crack monitoring and early warning is successfully demonstrated. This work presents a novel self-powered sensor for crack monitoring and early warning, such a strategy is potentially available for distributed sensor construction towards structural health monitoring (SHM) of the infrastructure.