High-Strength Superstretchable Helical Bacterial Cellulose Fibers with a "Self-Fiber-Reinforced Structure".

As a hydrogel membrane grown on the gas-liquid interface by bacterial culture that can be industrialized, bacterial cellulose (BC) cannot give full play to the advantages of its natural nanofibers. Conversion to the properties of nanofibers from high-performance to macrofibers represents a difficult material engineering challenge. Herein, we construct high-strength BC macrofibers with a "self-fiber-reinforced structure" using a dry-wet spinning method by adjusting the BC dissolution and concentration. The macrofiber with a tensile strength of 649 MPa and a strain of 17.2% can be obtained, which is one of the strongest and toughest cellulose fibers. In addition, the macrofiber can be fabricated to a superstretchable helical fiber without adding other elastomers or auxiliary materials. When the helical diameter is 1.6 mm, the ultimate stretch reaches 1240%. Meanwhile, cyclic tests show that the mechanical properties and morphology of the fiber remained stable after 100 times of 100% cyclic stretching. It is exciting that the helical fiber also owns outstanding knittability, washability, scalability, and dyeability. Furthermore, superstretchable functional helical BC fibers can be fabricated by embedding functional materials (carbon materials, conductive polymers, etc.) on BC or in the spinning dope, which can be made to wearable devices such as fiber solid-state supercapacitors. This work provides a scalable way for high-strength superstretchable and multifunctional fibers applied in wearable devices.