Thermal responsive smart lanthanide luminescent hydrogel actuator

Among stimuli-responsive soft materials, thermal responsive hydrogels are the most attractive one because temperature is the most easily regulated external stimuli. We here report a thermal responsive bilayer smart luminescent hydrogel actuator with tough mechanical strength and thermal reversible deformation behavior. The bilayer hydrogel is composed of Poly(N-isopropylacrylamide)-Laponite-Tb complex (PNIPAM-Lap-Tb·L3) layer and Poly(N,N-dimethylacrylamide)-Laponite-Eu complex (PDMA-Lap-Eu·L3) layer. Upon alternative heating and cooling, the PNIPAM-Lap-Tb·L3 layer undergoes reversible shrink and expansion, while the PDMA-Lap-Eu·L3 layer is not affected, leading to asymmetric deformation behavior. The luminescent intensity of the bilayer hydrogel was enhanced by heating, and the maximum bending angle was 371° in 15 min. By processing the bilayer hydrogel into complex 2D and 3D structure, we further demonstrate their great potential as smart soft actuators.