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

Abstract

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.

Strong, Antifatigue, and Ionically Conductive Organogels for High-Performance Strain Sensors

“…A hydrogel is a flexible and soft material containing a cross-linked polymeric network in a large quantity of water, and has shown wide applications in biomaterials and bioelectronics because of their intriguing properties such as biocompatibility, adaptability and versatility. − However, high water content and nonuniform network lead to their weak mechanical properties, and hydrogels also possess poor freezing resistance. , Furthermore, due to continuous water evaporation, hydrogels are easily dried in air, causing extreme instability in mechanical and electrical performance and hence severely limiting their practical applications. − …”

Multi-role conductive hydrogels for flexible transducers regulated by MOFs for monitoring human activities and electronic skin functions

“…Hydrogels, characterized as a class of soft water-based materials, present substantial promise for incorporation into wearable sensors owing to their exceptional biocompatibility, elevated stretchability, and customizable conductivity. 17–19 To make hydrogels suitable for a diverse array of applications, researchers have implemented a variety of techniques, including chemical cross-linking, 20–22 composite hydrogels, 23–25 double-network hydrogels 26–28 etc. Yet, for hydrogels to be appropriate for flexible transducers, they must possess formidable mechanical resilience and robust self-recovery to facilitate large-range strain sensing and enduring cycling stability.…”

Regulating Boronic Ester Bonds in Bilayer Hydrogels toward Fabricating Multistimuli-Triggered Actuators

“…For the reported hydrogels comprising dynamic B–O bonding, however, the current focus is mainly on diversifying sensing scenarios and improving overall performance when the hydrogels are used as flexible sensors. ,− In this case, the role played by dynamic B–O bonding is clear but very limited: acting as sacrificial (weak) bonding to protect primary networks or as a responsive unit to endow the system with temperature- or pH-sensing ability. Could the pH- and temperature-sensitive B–O bonding play the roles of structural and responsive units simultaneously in a conductive hydrogel with a heterogeneous network structure and could more application scenarios or working modes be unlocked for the B–O bonding-based hydrogels are worthy of exploring.…”