Self-Healable Conductive\nNanocellulose Nanocomposites\nfor Biocompatible Electronic Skin Sensor Systems

Abstract

Electronic skins are developed for applications such\nas biomedical\nsensors, robotic prosthetics, and human–machine interactions,\nwhich raise the interest in composite materials that possess both\nflexibility and sensing properties. Polypyrrole-coated cellulose nanocrystals\nand cellulose nanofibers were prepared using iron­(III) chloride (FeCl₃) oxidant, which were used to reinforce polyvinyl alcohol\n(PVA). The combination of weak H-bonds and iron coordination bonds\nand the synergistic effect of these components yielded self-healing\nnanocomposite films with robust mechanical strength (409% increase\ncompared to pure PVA and high toughness up to 407.1%) and excellent\nadhesion (9670 times greater than its own weight) to various substrates\nin air and water. When damaged, the nanocomposite films displayed\ngood mechanical (72.0–76.3%) and conductive (54.9–91.2%)\nrecovery after a healing time of 30 min. More importantly, the flexible\nnanocomposites possessed high strain sensitivity under subtle strains\n(<48.5%) with a gauge factor (GF) of 2.52, which was relatively\nlarger than the GF of ionic hydrogel-based skin sensors. These nanocomposite\nfilms possessed superior sensing performance for real-time monitoring\nof large and subtle human motions (finger bending motions, swallowing,\nand wrist pulse); thus, they have great potentials in health monitoring,\nsmart flexible skin sensors. and wearable electronic devices.