Braiding Ultrathin Au Nanowires into Ropes

Braiding is a common skill in daily life but rare at the nanoscale. Most of the current nanohelices are directly grown or assembled without involving mechanical interactions, and they are thus distinctively different from ropes in terms of functions and mechanisms. Here, by coaxially twisting multiple ultrathin Au nanowires, nanoropes are synthesized with elegant helical patterns that are consistent with the macroscopic equivalents. The strain relaxation of lattice transformation causes the nanowires to pursue the maximum degree of twisting, while the mutual packing interactions in a bundle prevent sideways emergence of U-turns. The consistent chirality of the seemingly independent strands can only arise when a first twisting strand causes morphological deformation in its neighbors, which induces the collective uni-directional twisting. The spontaneous braiding and the "remote" control of the nanowires involve mechanical interactions and possibly energy transmission, thus opening doors to chiral assembly and future smart nanodevices.