Top-down peeling bacterial cellulose to high strength ultrathin films and multifunctional fibers

Abstract

• BC nanofiber alignment was achieved via a simple one-step solvent-assisted drawing. • It is the first time to realize the peeling of BC film layer by layer to obtain BC ultrathin film. • The ultrathin film simultaneously exhibited high tensile strength (758 MPa) and high toughness (42.3 MJ m −3 ). • The BC ultrathin film can be twisted to super strong fibers or multifunctional fibers. • The fiber exhibited high tensile strength (954.2 MPa) and the record high toughness (93.2 MJ m −3 ). The materials with highly aligned tight arrangement at nano- and molecular level exhibit extraordinary mechanical properties. Bacterial cellulose (BC) is a three-dimensional network hydrogel formed by layers of disordered nanofibers generated by bacteria. Because of the disordered arrangement of nanofibers and the strong interaction between nanofibers, it is impossible for BC to give full play to the excellent mechanical properties of nanocellulose. In this paper, we first adopted an easily realized method to obtain high strength BC ultrathin film with highly aligned tight nanofiber structure. First, the hydrogen bond between nanofibers was weakened by simple solvent replacement, and then we stretched the BC hydrogel to 20−40% to realize the nanofiber alignment. After by hot-pressing drying, we first realized the peeling of BC film layer by layer to obtain the high strength ultrathin films inspired by graphene peeling method. The highest strength of the obtained film with thickness of 4–10 µm was up to 758 MPa and the toughness up to 42.3 MJ m −3 . By further twisting the films, very strong and tough fibers were obtained with high strength of 954.2 MPa and the record high toughness of 93.2 MJ m −3 . Furthermore, functional BC fibers can be achieved by embedding functional materials (dyes, functional nanomaterials, carbon nanotubes, etc.) in the ultrathin films before twisting. Our research first realized the transformation from BC hydrogel to ultrathin films and fibers with high strength and toughness. This work will pave the way for the application of BC hydrogel as high-strength flexible electronic device substrates, medical fibers, and wearable electronics.