Ultrasensitive microwave near-field based sensors for crack detection in metallic materials

This paper presents an ultrasensitive microwave sensor based on electrically small resonators. The resonators are inspired by complementary split-ring resonators (CSRRs) and designed as near-field sensor for crack detection in metallic materials. The sensor is designed by etching out a resonator in the ground plane of a microstrip line technology. The sensors shows not only high sensitivity (increasing dynamic range of the sensor) but also high spatial resolution, design simplicity and scalability. The sensor is able numerically to resolve a crack of 10 um (equivalent to λ/4000), with 186 MHz shift in the resonance frequency.