Stimulus-Responsive Graphene with Periodical Wrinkles on Grooved Microfiber Arrays: Simulation, Programmable Shape-Shifting, and Catalytic Applications

This
work demonstrates a facile fabrication of stimulus-responsive,
periodically wrinkled graphene sheets on grooved microfiber arrays
with fast and reversible shape change, multiresponsiveness, and programmable
deformation, with the aid of finite element analysis (FEA). The cellulose
acetate (CA) microfibers, endowing responsiveness to humidity and
solvents, are designed to grooved shape and assembled into a well-aligned
fibrous mat by electrospinning. Under the guidance of FEA simulation,
the stiff reduced graphene oxide (RGO) sheets, serving as a photoresponsive
component, could ably bind on grooved CA microfibers with favorable
interlocked interfacial-structure. Through simple direct-writing and
hot-pressing, the grooved CA arrays interlocked the conformal RGO
sheets by water-induced self-clamping, and enabled the generation
of periodic wrinkles within RGO sheets to maximize interfacial areas.
By simply adjusting the orientation of written RGO patterns relative
to uniaxial CA microfibers, programmed and omnidirectional shape-shifting
were obtained to minimize strain energy, consisting with the dynamic
deformation process simulated by FEA. Upon remote light or contactless
humidity stimuli, the RGO/CA mat shows a rapid response (≤1
s), large amplitude (angle change ≥150°, 1.62 cm–1), sophisticated 3D motions, and lifts objects that weigh 12.7-times
its own weight up to over 1/3 of own height within 1 s. After loading
catalytical nanoparticles, the RGO/CA mat could rapidly move to the
targeted position by continuous crawling even on a slippery surface,
and served as a microchannel reactor to trigger a reaction in built-in
microchannels with suppressing catalyst leaching while accelerating
reaction kinetics by both nanoconfinement and photothermal effect.