As more and more inorganic ultra-fine nanowires are synthesized, their applications in optics, electricity, and magnetism have attracted widespread interest. Conventional inorganic nanowire fibers are generally not stretchable and have little elasticity, which limits its practical application. Ultrafine inorganic nanowires are similar in size and structure to polymer chains, so wet spinning and electrostatic spinning have been used to make nanowire fibers. To date, Bi2S3, gold and hydroxyapatite nanowire fibers have been obtained by wet spinning, and GdOOH nanowire fibers have also been obtained by electrostatic spinning. The obtained nanowire fibers have good optical or mechanical properties. Due to the lack of a proper hierarchical structure, the nanofiber fibers obtained so far have low stretchability and elongation at break.
Wang Xun's team at Tsinghua University was inspired by the helical cellulose in cherry bark and applied this characteristic to the manufacture of flexible nanowires. GdOOH nanowire spinning dope having a length of hundreds of nanometers and a diameter of less than 1 nanometer is wet-spun to produce nanowire fibers. Under the influence of injection stress, shear force and solvent exchange. By controlling the spinning dope, coagulation bath, flow rate, etc., an ordered spring-like nanowire structure can be obtained. Thereby, highly stretchable flexible nanowire fibers are obtained. The elongation at break of the nanowire fiber can usually reach 40-50%, and the highest elongation can reach 86%. And the nanowire fiber will not produce any cracks under the conditions of winding, bending and twisting. According to the structural transformation in the tensile test and the synchrotron small-angle X-ray scattering (SAXS) study, it is concluded that the neat spring-like nanowires in the fiber assembled superlattice are the main reasons for this characteristic. And by adding inorganic nanoparticles, the nanowire fiber can be further strengthened and toughened.