Synergistic pH and Temperature Driven Actuation of Poly(NIPAM-co-DMAPMA)/Clay Nanocomposite Hydrogel Bilayers
ABSTRACT: Hydrogel actuators that deform in response to external stimuli have promising applications in diverse fields. It is desired to develop robust hydrogels with multiple and synergistic stimuli responsiveness. This work reports on robust poly(NIPAM-co-DMAPMA)/clay hydrogel bilayers that undergo reversible and repeatable curling/uncurling in response to pH and/or temperature changes. The bilayers are fabricated by sequential synthesis of thermoreponsive N-isopropyl acrylamide (NIPAM) and N-[3-(dimethylamino)propyl] methacrylamide (DMAPMA) monomers, which produces robust interface bonding between the layers. Different NIPAM/DMAPMA ratios between two gel layers were used to manipulate the
asymmetric responsiveness, and thus lead to curling/uncurling of bilayers upon stimuli. The hydrogel bilayers are fabricated into soft manipulators to grasp-and-release target objects by pH and temperature changes, and as artificial muscle to lift and move the hanging weight by synergistic pH and temperature stimuli. This work provides a new type of asymmetric responsive hydrogel bilayers with potential applications in biomimetic actuators.