Tannic acid modified hemicellulose nanoparticle reinforced ionic hydrogels with multi-functions for human motion strain sensor applications

Recently, biomass-derived materials, such as cellulose and lignin have gained popularity in the development of value-added products, such as hydrogel-based sensors. In fact, many studies have been reported on the inclusion of cellulose or lignin or their derived products for the preparation of hydrogels and their sensing applications, hemicelluloses-based hydrogels and their sensing applications are rare. In this study, we used a hemicellulose sample extracted from a bleached bamboo kraft pulp, to prepare hemicellulose nanoparticles (HC nanoparticles), then modified the HC nanoparticles with tannic acid to form tannic acid modified hemicellulose nanoparticles (TA@HC). Subsequently, the TA@HC nanoparticles were applied as nanofillers in the fabrication of ionic PAA-TA@HC-Al3+ hydrogels. The hydrogel integrates covalent PAA bonds with multiple non-covalent coordination bridging. TA@HC nanofillers, which have catechol-rich tannic acids on the surface, act as strength enhancers and dynamic link bridges, as well as imparting self-healing/adhesive properties to the ionic hydrogel. The resultant PAA-TA@HC-Al3+ ionic hydrogel exhibits high stretchability (1060%), toughness (as high as 1.52 MJ/m(3)) and self-recovery (as high as 87%). In addition, the use of TA@HC nanofillers allows the hydrogel to have reproducible self-adhesion to various materials, furthermore, the ionic hydrogel has excellent anti-ultraviolet, anti-oxidative and antibacterial properties. When applied as a wearable strain sensor, the as-fabricated ionic hydrogel has a high strain sensitivity (GF=8.34), and it can accurately monitor and distinguish between large movements and micro movements, even weak pulse and breathing.