Reversible fiber fusion and fission
Materials that can cycle between states are of interest for actuators, soft robotics, or recoverable membranes for separations. Chang et al. show that a collection of graphene oxide fibers can fuse into a single stronger fiber upon immersion in a solvent, extraction, and drying under tension (see the Perspective by Cruz-Silva and Elías). The geometrical deformation of the fibers during drying and swelling plays an important role in the reversible cycles, with a large volume change between the dried and swelled fibers. Moreover, fibers made from polymers, glass, metal, or silk can be given these abilities when coated with a micron-sized layer of graphene oxide.
Stimuli-responsive fusion and fission are widely observed in both bio-organizations and artificial molecular assemblies. However, the design of a system with structure and property persistence during repeated fusion and fission remains challenging. We show reversible fusion and fission of wet-spun graphene oxide (GO) fibers, in which a number of macroscopic fibers can fuse into a thicker one and can also separate into original individual fibers under stimulation of solvents. The dynamic geometrical deformation of GO fiber shells, caused by solvent evaporation and infiltration, is the key to the reversible fusion-fission cycles. This principle is extended to implement flexible transitions between complex fiber assemblies and the inclusion or expulsion of guest compounds.