High-performance, breathable, and degradable fully cellulose-based sensor for multifunctional human activity monitoring

High-performance flexible piezoresistive pressure sensors have garnered considerable attention for health monitoring and medical diagnostics. However, achieving both high sensitivity and a wide detection range is often limited by complex, costly microstructural designs. Furthermore, the non-degradability of many sensing materials poses environmental challenges. Here, we present an innovative, flexible, fully degradable pressure sensor based entirely on cellulose-based paper and MXene. Utilizing a cost-effective dip-coating method, MXene was uniformly deposited onto cellulose-based paper substrates with six distinct fiber microstructures, including natural fibers (cellulose I) and viscose fibers (cellulose II), forming a conductive sensing layer. The sensor, featuring a sandwich structure with the core sensing layer and cellulose paper-based encapsulation layers, demonstrates high sensitivity (36.87 kPa-1for 0-1.3 kPa), 11.39 kPa-1 for 1.3-60 kPa, 1.25 kPa-1 for 60-79 kPa), a wide pressure range (0-79 kPa), a lower detection limit (3.7 Pa), and fast response/recovery times (113 ms/81 ms). The sensor also shows excellent cyclic stability and can detect both dynamic and static pressures, making it suitable for monitoring physiological signals such as speech vibrations, finger movements, and wrist pulses. Significantly, this sensor is fully biodegradable under natural conditions within 58 days, offering an environmentally sustainable and cost-effective solution for the future of wearable electronics.