A Multiresponsive Anisotropic Hydrogel with Macroscopic 3D Complex Deformations

As one of the most promising smart materials, stimuli-responsive polymer hydrogels (SPHs) can reversibly change volume or shape in response to external stimuli. They thus have shown promising applications in many fields. While considerable progress of 2D deformation of SPHs has been achieved, the realization of 3D or even more complex deformation still remains a significant challenge. Here, a general strategy towards designing multiresponsive, macroscopically anisotropic SPHs (MA-SPHs) with the ability of 3D complex deformations is reported. Through a local UV-reduction of graphene oxide sheets (GOs) with a patterned fashion in the GO-poly(N-isopropylacrylamide) (GO-PNIPAM) composite hydrogel sheet, MA-SPHs can be achieved after the introduction of a second poly(methylacrylic acid) network in the unreduced part of GO-PNIPAM hydrogel sheet. The resulting 3D MA-SPHs can provide remote-controllable light-driven, as well as thermo-, pH-, and ionic strength-triggered multiresponsive 3D complex deformations. Approaches in this study may provide new insights in designing and fabricating intelligent soft materials for bioinspired applications.