Wire-based triboelectric resonator for a self-powered crack monitoring system

In this study, we investigated a wire-type triboelectric resonator (WTER) for monitoring cracks. Vibration of a metal wire on a dielectric film produces a resonant frequency via triboelectric outputs. We found that the tension, linear density, and wire length significantly affect the resonant frequency measured by the WTER. For a 10-cm-long wire, the WTER's sensitivity, as defined by a resonant frequency change for an elongation (i.e., Hz/mm), reached approximately 1,020 Hz/mm; however, this changed to 115 Hz/mm after an elongation of 1.5 mm. When a 40-cm-long wire was used, the sensitivity changed to about 105 Hz/mm, but it was very stable because there was no plastic deformation. We developed a stand-alone, self-powered crack monitoring system by assembling a WTER with an Arduino board (A-WTER); this setup demonstrated monitored frequency value errors of less than 1%. Our A-WTER successfully monitored an elongation of 100 μm with a resonant frequency change of approximately 30 Hz. We investigated the A-WTER behavior under varying humidity and temperature conditions in order to understand its environmental stability. We found it was highly stable through a broad humidity range (RH 10%–80%) while its thermal stability was controlled by changing the tension and length of the wire.