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

Developing a "one-step"method simultaneouslybuilding chemical crosslinks and ionic paths for fabricating cellulose-containinghydrogel sensors with environmental adaptability. Cellulosenanofibers are one of the most frequently used fillersfor reinforcing hydrogels. The reinforcement, however, is commonlyaccompanied by the decrease of deformability. Inspired by the armorstructured with overall flexible but locally rigid characteristics,we proposed a strategy of constructing chemical networks of bacterialcellulose (BC) in this work to improve the overall mechanical performanceof hydrogels. The PAM hydrogels with borax-crosslinked BC nanofiberswere prepared. The BC networks are multiscaled, and different levelsof structures play different roles. As the flexible networks, thecrosslinked 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 "sacrificialbonds", improving the fatigue resistance to the cyclic tensilewith large strain (500%). The mechanical strength of the hydrogelsis also significantly enhanced due to the reinforcement role of BCnanofibers. Moreover, the remained sodium ions and borate ions givethe hydrogels good conductivity and decreased freezing point. Accordingly,the as-prepared flexible sensor has superior sensitivity (Gauge factor10.1 for stretching) with satisfactory environmental adaptability.This work proposes an effective strategy of structural regulationfor the cellulosic particle-containing hydrogel to improve the overallperformance.