Biological soft tissues execute sophisticated functions and present dynamic shape changes via nonequilibrium structural transformations. However, artificial intelligent materials mainly rely on equilibrium or quasi-equilibrium processes to respond to external stimuli, exhibiting limited functions and monotonical responsive behaviors. Here, we report a hydrogel with hierarchically confined polymer networks to mimic nonequilibrium and multimodal shape changes in nature. It is prepared from a facile one-step radical polymerization employing a hydrophilic monomer and a hydrophobic monomer. The hydrogel shows many attractive features, including reversible color changes and unusual shape-shifting behavior via a far-from-equilibrium process. The autonomous off-equilibrium flat-to-3D shape-morphing behavior is spatially controlled by local mismatches of shape recovery kinetics from thickness direction. During the stress-triggered shape-shifting process, the programmed stress induces uneven water diffusion in hierarchical confinement structures, which pushes the hydrogel off the equilibrium-based natural pathway, creating self-evolving opposite shape-shifting events with time. Furthermore, a “live” 4D far-from-equilibrium morphing, with bright color changes, is demonstrated under the polarizer. We believe that this work will inspire future research on creating otherwise unattainable functional hydrogels via nonequilibrium structure transformations.

Nanoconfinement-induced far-from-equilibrium stimuli-responsiveness

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