Fig. 1: Design and fabrication of STIFs.

a Schematic diagram of the preparation of BSNH slurry using a “grafted from” method by copolymerization of AAm and iAA on the modified nanocomposite initiator CNF@AgNPs@MMMP. b Schematic diagrams of the fabrication of STIFs by dry-spinning combined assembly-assisted solvent-exchange method. Firstly, the BSNH fibers with entangled CNF@AgNP skeletons were obtained by a dry-spinning process. By stretching the hydrogel fibers along the long axis and twisting, a temporarily elongated architecture was constructed with a helical configuration. After immersing in ionic liquid EMIES, the STIFs were finally fabricated. The trajectories of water molecules illustrated the dehydration process. c Evolution of hierarchically anisotropic structure with seamless interfaces. The CNF@AgNPs skeletons with high aspect-ratio were aligned and packed by dry-spinning, forming a nanoconfined polymer network which was further strengthened in the subsequent prestretch and twisting process. Upon solvent exchange with EMIES, the nanoconfined PAAm chains were separated from matrix to generate hard phase owing to the selectively strengthened hydrogen bonds between PAAm chains, enabling the tight interfacial connection between filaments.