Near-infrared responsive shape memory hydrogels with programmable and complex shape-morphing

In this work, semi-crystalline nanocomposite hydrogels (i.e., PAAmA11A/GO gels) were synthesized by micellar copolymerization of acrylamide and N-acryloyl-11-aminoundecanoic acid (A11A) in the presence of a large amount of sodium dodecyl sulfonate (SDS) micelles and GO nanosheets. The resulting hydrogels (SMHs) not only demonstrated high strength and high toughness, but also exhibited good shape memory property. Because of near-infrared (NIR) light absorbability of GO nanosheets, shape recovery and shape of PAAmA11A/GO gels could be tuned by NIR irradiation. Moreover, bilayer hydrogels and trilayer hydrogels were also fabricated by the integration of shape-memorized PAAmA11A/GO gel and elastic hydrophobic associated hydrogel (E-gel). Based on the NIR-responsive shape memory property and layered structure, shape deformation of bilayer hydrogels and trilayer hydrogels was rather different from the single PAAmA11A/GO gel. Each kind of gel structure exhibited diverse and complex shapes via programmable NIR irradiation. More importantly, the shape morphing of NIR-SMHs-based hydrogels could mimic the hand and flower and be used as actuators.