It is a great challenge to study the mechanical property of nanomaterials because it is difficult to get a hold of them and apply force. A convenient alternative method via electrospun fibers is shown, where silica‐coated fivefold twinned silver nanowires are well aligned in the fiber and the fibers are aligned in the membrane to a similar direction of macroscopic stretching. The product silver nanowires show necks whereas the fractured silica shell acts as the internal marker for the extent of stretching. Surprisingly, the stretched neck length depends on the nanowire diameter but is independent of the degree of stretching, indicating that the necks have arrived at a limiting intermediate state, which is otherwise hard to achieve for nanomaterials. The necks are studied by transmission electron aberration‐corrected microscopy and steered molecular dynamics simulation, revealing that the build‐up of dislocations and stacking faults (the Lomer–Cottrell (LC) locks) are responsible for trapping the necks at similar limiting states.

We demonstrate that ripening could turn highly anisotropic Ag nanorods into Janus nanorods (lollipops), and eventually spherical nanoparticles. The divergent etching and growth on the Ag nanorods, and the morphology-specific...