Integrated Wireless Sensor System Featuring Liquid-Repellent Interfaces for Reliable Pressure Ulcer Monitoring

Continuous interface pressure monitoring is essential for proactive pressure ulcer (PU) prevention, yet the reliability of flexible capacitive sensors is frequently compromised by the accumulation of sweat and biofluids in clinical settings. The fundamental challenge arises from the significant dielectric mismatch between aqueous fluids and sensor materials, where fluid infiltration leads to severe signal distortion. Here, we present a liquid-immune wireless sensor system that leverages a robust superhydrophobic interface to eliminate this interference. The sensor unit features a hierarchical design combining a PDMS/MWCNT interlocking dome-array microstructure for pressure transduction with a spray-coated silica nanoparticle layer. Mechanistically, this surface engineering establishes a stable Cassie-Baxter state, trapping a persistent air plastron that physically isolates the sensing element from high-permittivity contaminants. Consequently, the device achieves a broad detection range (0-1.2 MPa) with a sensitivity of 5.22 × 10⁻³ kPa⁻¹, while maintaining exceptional signal integrity even after 5000 compression cycles at 1.15 MPa and 24 h immersion in blood and tissue fluids. To realize a clinically viable platform, we integrated the sensor array with a custom smartphone application featuring built-in risk assessment algorithms. This user-centric interface provides intuitive visualization of pressure distributions via dynamic color-coded heatmaps and triggers intelligent alerts based on cumulative pressure-time exposure, offering a practical, artifact-free solution for proactive chronic wound management.