Crosslinking of Bacterial Cellulose toward Fabricating Ultrastretchable Hydrogels for Multiple Sensing with High Sensitivity

Cellulose nanofibers are one of the most frequently used fillers for reinforcing hydrogels. The reinforcement, however, is commonly accompanied by the decrease of deformability. Inspired by the armor structured with overall flexible but locally rigid characteristics, we proposed a strategy of constructing chemical networks of bacterial cellulose (BC) in this work to improve the overall mechanical performance of hydrogels. The PAM hydrogels with borax-crosslinked BC nanofibers were prepared. The BC networks are multiscaled, and different levels of structures play different roles. As the flexible networks, the crosslinked BC endows the hydrogels with superior stretchability (7710%) and improves anticutting property as well as crack growth resistance. The crosslinks composed of boronic ester bonds act as "sacrificial bonds", improving the fatigue resistance to the cyclic tensile with large strain (500%). The mechanical strength of the hydrogels is also significantly enhanced due to the reinforcement role of BC nanofibers. Moreover, the remained sodium ions and borate ions give the hydrogels good conductivity and decreased freezing point. Accordingly, the as-prepared flexible sensor has superior sensitivity (Gauge factor 10.1 for stretching) with satisfactory environmental adaptability. This work proposes an effective strategy of structural regulation for the cellulosic particle-containing hydrogel to improve the overall performance.