We report the influence of multi-walled carbon nanotube (MWCNT) incorporation on the infrared (IR)-induced thermoresponsive bending behavior of poly( N -isopropylacrylamide)/polyethylene glycol diacrylate bilayer hydrogels. The bending deformation rate depends on the MWCNT content: at relatively low loadings, increasing MWCNT content increases the deformation rate, while higher loadings suppress it. This behavior can be primarily attributed to the mechanical properties, swelling capabilities, and thermal conductivities of the hydrogel. Specifically, variations in the swelling ratio, elastic modulus, and thermal conductivity of the bilayer hydrogels collectively govern the bending deformation rate. Thus, the IR-induced bending motion can be finely tuned by varying the MWCNT content. We further demonstrate functional utility by lifting of a small object by the hydrogel under IR irradiation.
Sasaki et al. (Mon,) studied this question.