Pre-Compressed Conductive Sponge Pressure Sensor with Reduced Hysteresis for Sustained Interface Pressure Monitoring

Abstract

Skin-interface pressure monitoring is essential for preventing pressure injuries caused by sustained mechanical loading between the human body and support surfaces. However, porous structure-based pressure sensors often exhibit high mechanical hysteresis and unstable response because of their intrinsic viscoelastic deformation and structural instability under repeated deformation, hindering reliable detection of sustained interface pressure. Herein, we report a fully flexible piezoresistive pressure sensor based on a carbon black (CB)/polydimethylsiloxane (PDMS)/ethyl cellulose (EC)-coated polyurethane (PU) sponge integrated with Ag nanowire (AgNW)-patterned textile electrodes. EC facilitated the formation of a continuous conductive coating on the PU sponge, while the pre-compression process during curing effectively reduced the mechanical hysteresis of the porous structure. The fabricated sensor exhibited a sensitivity of 0.019 kPa⁻¹ in the low-pressure range of 0−19 kPa, a broad sensing range up to 185 kPa, and stable cyclic performance over 3000 compression cycles of 100 kPa. The sensor enabled real-time monitoring of interface pressure at pressure-vulnerable body sites during postural changes. In addition, a pilot study with six participants of different body weights demonstrated the ability of the sensor to detect site-dependent interface pressure and body weight-related pressure trends. These results suggest that the developed sensor has potential for continuous interface pressure monitoring in healthcare and rehabilitation applications.