▎ 摘　　要

Recently, adaptive programmable materials capable of changing their shape to perform complex motions in response to an external stimulus have attracted tremendous interest. The shape-changing abilities rely heavily on the non-linear response of a localized area, where generally an external stimulus would cause distortion due to non-uniform volumetric changes. Hence, creating materials with heterogeneous compositions and structures have become an effective strategy to achieve the non-uniform volumetric changes. Here, a versatile strategy that harnesses the concepts of structural and compositional gradients to guide the design of programmable light-activated materials with continuous changing structures and their correspondingly responsive behavior are developed. These materials compose of a bilayer structure including ultraviolet-cured Norland Optical Adhesive (NOA) 73 support layer and a structural and compositional gradient layer of polyethylenimine (PEI)-modified graphene oxide (GO) complexes. The volumetric mismatch between these two layers leads to the reversible three-dimensional deformation of PEI-GO/NOA 73 bilayers. The PEI density and the extent of GO reduction lead to different light-sensing abilities, which result in different extent of deformation and deformation/reversal speed. By controlling the composition of each PEI-GO segment, programmable light-activated actuations, such as helical buckling with varying pitch-sizes of a gradient-based PEI-GO/NOA 73 actuator are demonstrated.