Dual‐Channel Flexible RFID Tag Sensor Based on Liquid Metal for Multi‐function Sensing Applications

ABSTRACT Structural health monitoring (SHM) technology is widely used in aerospace, civil, and mechanical fields to enable real‐time damage detection and prevent failures in metallic structures. To address challenges in sensor deployment and multi‐functional integration, this study presents a liquid metal‐based dual‐channel wireless passive RFID tag sensor capable of simultaneous crack, strain, and temperature sensing. The proposed sensor operates wirelessly by tracking resonant frequency shifts associated with the RFID tag's activation threshold power using a reader. Crack detection sensitivities reach 10.6 MHz/mm ² (Channel 1) and 9.8 MHz/mm ² (Channel 2). Normalized strain sensitivities are 2.08 and 2.09 kHz/µε in inward/outward bending configurations, while temperature sensitivities are 0.286 and 0.283 MHz/°C for the two channels. By implementing a differential measurement strategy between two channels, the sensor allows for crack orientation discrimination while effectively suppressing environmental interference.