Macrofibers with tunable mechanical performance and reversible rotational motion based on a bacterial cellulose hydrogel film

Mechanically twisting a yarn is a useful and important method for creating internal stress, changing macromolecular orientation, and affording interesting fiber properties, including mechanical, structural, physical and chemical properties. Bacterial cellulose (BC) nanofibers are a new type of highly crystalline bionanofibers exhibiting excellent intrinsic mechanical properties. Herein, BC macrofibers with a diameter of 0.35-0.53 mm were prepared from BC hydrogel films using a two-step technique involving drying and twisting processes. Moreover, the effects of the drying method (oven- and freeze-drying) and those of the processing steps on the morphologies, structures, and physicochemical properties of the macrofibers were investigated. Results indicated that only the wet twisting-first process affords continuous macrofibers with a compact and uniform structure. The tensile strength and elongation at break of the macrofibers were 199 MPa and 24%, respectively. Furthermore, by introducing graphene oxide (GO) to the macrofibers, a photothermal and moisture actuator was facilely constructed, which could produce a twisting motion of 0.39 rpm and an untwisting motion of 0.6 rpm. This study