High Sensitivity Wireless Strain Sensor for SHM Applications

Our research aims to develop a new generation of ultrasensitive strain sensors with wireless communication of data and energy, low power consumption, and easy installation within structures to be used as in-situ measurement systems. The sensor has been developed based on RFID sensing technology that allows wireless data and power transmission by inductive coupling between the internal inductance of the sensor and the external readout coil. Microfabrication technology is used to fabricate the sensor by patterning a metallic LC circuit on a flexible substrate. Nano cracks are introduced to the electrode to create a piezoresistive effect that leads to a transmission line behavior of the capacitance electrodes. The sensor has been embedded with GFRP and CFRP, a bending test has been performed, and the sensor is used to measure the strain during the test. The sensor proves its ability to detect small strains in the composite structures due to the unconventional change in capacitance of the LC oscillator. This unconventional change in capacitance results in a large shift in resonance frequency, producing a sensitive wireless strain sensor with a Gauge factor of 50 for less than 1% strain.