All-Paper-Based, Flexible, and Bio-Degradable Pressure Sensor with High Moisture Tolerance and Breathability Through Conformally Surface Coating

Highlighted with bio-degradability, paper-based flexible pressure sensors receive significant attention in the field of wearable devices for a sustainable future. However, it remains a challenge to possess considerable sensing performance in high humidity and underwater environments, because its structure rapidly breaks down after the hydrophilic cellulose absorbs water. In this study, a facile chemical vapor deposition method is employed to conformally coat a thin hydrophobic layer onto the cellulose fibers, resulting in an encapsulating paper with high moisture tolerance. The well-maintained porous structure reserves the superior breathability of the paper. A micro-convex-structured sensor layer impregnated with MXene serves as the sensing layer. As a result, an all-paper-based pressure sensor with high moisture tolerance and breathability is fabricated. This sensor features a broad sensing range (0–60 kPa), acceptable sensitivities (39.58 kPa⁻¹ (0–1.01 kPa), 11.95 kPa⁻¹ (1.01–60 kPa)), a low detection limit of ≈2.8 Pa, response and recovery time (93 and 69 ms), reliable hydrophobic breathability, and excellent repeatability (10 000 cycles). Moreover, this sensor can be safely worn on human skin and can monitor physiological signals in real-time in different environments (including air, humid environments, and even underwater), providing a reliable, economical, and environmentally friendly solution for wearable technology.