Synergistic stretching-annealing and salting-out enabling ultrastrong, ultratough anisotropic bacterial cellulose conductive hydrogels for bioelectric sensors

Abstract

Developing high-performance hydrogels that simultaneously exhibit biocompatibility, exceptional strength, toughness, conductivity, and antibacterial properties is crucial for meeting the stringent demands of bioelectric signal monitoring. Herein, we present an integrated approach for designing anisotropic bacterial cellulose (BC) hydrogels (PBA/K-a%) involving stretching the as-prepared polyvinyl alcohol (PVA)-BC-2-acrylamido-2-methylpropanesulfonic acid (AMPS) hydrogels (PBA) to various elongation ratios (a%), followed by air-drying during annealing to align the polymer chains, and finally immersed in potassium citrate (K₃Cit) solutions to enhance the polymeric interactions via a synergistic stretching-annealing and salting-out (SSAS) strategy. This effective strategy improves molecular hydrogen and coordination interactions, enhances crystallinity, and induces the orientation of polymer chains and nanofibers along the stretching direction, significantly increasing the mechanical robustness of the hydrogels. Notably, the P_10%B_0.45%A_10%/K-100 % hydrogel demonstrates ultrahigh mechanical strength of 45.32 MPa, high strain of 838 %, and ultrahigh toughness of 256.26 MJ/m³, as well as good conductivity with 13.3 mS/cm. The cooperative incorporation of PAMPS and K₃Cit endows the hydrogel with good antibacterial capacity, establishing it as a unique and effective wearable sensor. Furthermore, the PBA/K-100 % hydrogel was successfully employed for the bioelectric signal monitoring of electrocardiograms (ECG) and electromyograms (EMG), thus demonstrating its potential applications in human-machine interactions and bioelectronics.