Humidity-driven modulation of conductive pathways in biodegradable CMC/MXene composite membranes for flexible humidity sensing

Non-nanoscale strategy enables high-performance flexible humidity sensing. • Synergistic CMC-MXene coupling amplifies humidity-induced transport response. • Ultrawide-range (11–97% RH) detection with a high response of 89.5%. • Excellent temperature stability, bending durability, and biodegradability. Flexible humidity sensors for wearable health monitoring and environmental sensing require simultaneously high sensitivity, operational stability, and environmental sustainability. However, most high-performance devices still rely on non-degradable polymers or elaborate nanostructured bio-based architectures. Here, we report a biodegradable resistive humidity sensor based on a vacuum-filtrated carboxymethyl cellulose (CMC)/MXene composite membrane. CMC provides abundant hydrophilic-OH and -COOH for efficient moisture adsorption, while MXene forms a percolated conductive network. Humidity-dependent XRD shifts indicate tunable MXene interlayer spacing within the CMC matrix, which modulates intersheet contacts and thus the effective conductive pathways, leading to an amplifies electrical response. The optimized sensor exhibits stable and highly reproducible responses over 11–97% relative humidity (RH), achieving a maximum humidity response value (-ΔI/I₀) of 89.5% at 97% RH, with a response/recovery time of 131/340 s. The device maintains performance underrepeated bending (100 cycles), long-term operation (10 days), and temperature variation. Importantly, the membrane shows rapid disintegration in soil within 30 days, offering a promising route toward high-performance yet sustainable flexible humidity sensing without nanocellulose fibrillation or complex device architectures. Download: Download high-res image (180KB) Download: Download full-size image