Development and Characterization of a Novel Interdigitated Capacitive Strain Sensor for Structural Health Monitoring

Monitoring of structural health plays a crucial role in condition-based maintenance and degradation prediction of infrastructures. In this paper, we developed a novel interdigitated capacitive (IDC) strain sensor which could be integrated in a wireless monitoring system for structural health monitoring (SHM) applications. The IDC sensors were fabricated by laser-micromachining a 127-μm-thick brass sheet followed by encapsulation in deformable thermoset polymers. The wireless monitoring system was implemented using a commercial wireless module (eZ430-RF2500 from Texas Instruments) which could provide multi-modality monitoring simultaneously. A graphical user interface was developed to display and store data as well as perform real-time analysis remotely. The wireless communication distance was up to 35 m inside buildings. The sensitivity of the sensor was characterized in both stretching and bending aspects, yielding a limit of detection with respect to strain of 0.025%. The gauge factor was found in the range of 6-9 which is much higher than those of commercially available strain gauges. The bending detection is reliable up to 20°. Hysteresis and temperature dependence were also investigated, revealing predictable responses. Finally, the entire system was demonstrated with both single and multiple sensors for a real-time SHM case.