stimuli-responsive hydrogels, so-called intelligent hydrogels, are able to reversibly alter their shape or volume in response to small environmental variations, e.g. temperature, pH, light, and so on.1 These environmentally sensitive hydrogels have potentially shown extensive applications in artificial muscles,2 drug delivery and release,3 on–off switches and actuators.4 Up to now, most of the commonly synthesized hydrogels possess isotropic structures integrated from the molecular level to macroscopic level. Such a conventional intelligent hydrogel undergoes a typical isotropic three-dimensional volume change in response to an external stimulus, which means the swelling/shrinkage along different directions is equal. In this paper, a macroscopically anisotropic PEG-CNTs-PNIPA hydrogel with a novel aligned triple-network microstructure has been fabricated. It displays a unique anisotropic volume change in response to a temperature, near-infrared, or electric stimuli.
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