Sensitive and reliable wireless monitoring of foot pressure and temperature for diabetic foot ulcer management and prevention

This study presents a wireless, fully passive sensing system for sensitive and reliable monitoring of foot pressure and temperature, aiming to advance the prevention and management of diabetic foot ulcers (DFUs), a prevalent complication of diabetes. The system employs an emerging non-Hermitian electronic platform, i.e., parity-time-reciprocal scaling (PTX) symmetry, to establish an exceptional point (EP). This unique singularity produces dramatic resonance frequency shifts in response to external perturbations, delivering exceptional sensitivity. Unlike traditional inductor-capacitor (LC) wireless sensors, where frequency tracking is highly susceptible to reader-sensor alignment, the proposed PTX-symmetric system benefits from its balanced dual-resonance feature, rendering it alignment-independent. The resistance changes on the reader side can directly mirror those on the sensor side, which corelate to the pressure and temperature variations. The system demonstrates reliable performance over a pressure range of 0–400 kPa and a temperature range of 25–50 °C, maintaining accuracy even with variations in reader-sensor distance, an inherent limitation of traditional inductively coupled sensors. Additionally, by employing a custom-made resistive pressure transducer, the sensor exhibits flexibility and softness, offering enhanced wearing comfort. Experiments validate that the system can capture foot pressure and temperature distributions under different postures and during dynamic activities (e.g., walking), thereby identifying high-risk areas for DFUs development. Comparative studies further reveal a correlation between DFU risk, body weight, and prolonged standing or walking, confirming its potential for DFU management and prevention.