Spiropyran based hydrogels actuators-Walking in the light

Herein we report on the synthesis of a bipedal hydrogel walker, based on N-isopropylacrylamide-co-acrylated spiropyran-co-acrylic acid p(NIPAAm-co-SP-co-AA). Due to the presence of the photochromic spiropyran molecule in the polymer structure, these hydrogels reversibly shrink and swell in aqueous environments when exposed to different light conditions. When placed onto a ratcheted surface, the actuation of the bipedal gel produces a walking motion by taking a series of steps in a given direction, as determined by the optimised design of the ratchet scaffold. We anticipate that such biomimetic hydrogel walkers could form the basis of light-actuated soft robots capable of more advanced functions, such as autonomous migration to specific locations accompanied by triggered release of molecular cargo. (C) 2017 Elsevier B.V. All rights reserved.