Experimental Characterization of Zero-Power RFID-Based Strain Sensor for Implanted Fixators

Digital healthcare revolutionizes medicine with pioneering technologies, advancing patient care through precise diagnoses, personalized therapies, and continuous monitoring outside clinical settings. Radio-Frequency IDentification (RFID) emerges as a key enabling technology for wireless, battery-less sensing, such as monitoring the strain of implanted fixators for remote fracture healing assessment. This paper, hence, focuses on the experimental characterization of the AS2313 IC by Asygn as a fully passive wireless strain sensor, comparing it with a wired strain gauge for reference. From the sensor characterization with a three-point bending test, the calibration curves were obtained for different internal amplifier’s gains, obtaining a maximum sensitivity of 20.6 µϵ/bit. Moreover, a negligible effect of hysteresis was observed, demonstrating the overall reliability of the sensor. Preliminary static and dynamic measurements were also conducted installing the board on a metal bar, emulating an implantable fixator. The system returned an instantaneous and accurate estimation of the stress across the fixator during a simulated walk, corroborated by an external wired strain gauge of reference.