A Battery-Less RFID-Enabled Capacitive Pressure Sensor Integrated in Textile Fabrics

This work presents a battery-less UHF RFID-enabled capacitive pressure sensor based on a multi-layer stacked capacitor (MLSC) architecture, where standard denim acts as a porous and compressible dielectric. An optimized four-layer denim–copper stack produces a nonlinear electromechanical response across the investigated pressure range of 0-4.4 kPa. The measured sensitivity decreases progressively with pressure, from 0.3 pF/kPa at low load to 0.163 pF/kPa at the upper end of the range, with an average sensitivity of 0.19 pF/kPa. Integrated with the capacitive sensing front-end of an EM4152 RFID chip and a conjugate-matched T-match dipole tag, the sensor achieves an empirical limit of detection of 833 Pa. Wireless characterization confirms reliable real-time capacitance monitoring and a maximum read range of approximately 13 m within the ETSI UHF band (865–868 MHz). The proposed platform demonstrates the feasibility of maintenance-free textile-integrated wireless pressure sensing for unobtrusive monitoring scenarios.