Wireless, Fully soft, Pressure and Temperature Sensors for Sensitive and Robust Diabetic Foot Ulcer Monitoring

This study introduces a wireless, fully soft sensor for the sensitive and robust monitoring of foot pressure and temperature, advancing the prevention and diagnostics of diabetic foot ulcers (DFUs). The sensing system leverages parity-time (PT) and PT-reciprocal scaling (PTX) symmetry, creating an exceptional point (EP) that induces rapid frequency shifts in response to sensing parameters, demonstrating high sensitivity. Additionally, the system's eigenfrequencies generate a pair of balanced resonant dips in the reflection spectra, enabling the accurate retrieval of pressure- and temperature-induced resistive perturbations by measuring the resistance of the reader, independent of reader-sensor alignment. The results indicate that the proposed sensing system can robustly monitor pressure (0-400 kPa) and temperature (25-50 °C) with various reader-sensor distances, effectively addressing the longstanding issue linked with inductively coupled passive sensors. Moreover, by integrating a custom-made resistive pressure transducer, the proposed sensor remains fully flexible and soft, showcasing significant potential for DFU management and a broad spectrum of wearable healthcare applications.