Method for photo-curing four-dimensional (4D) printing of multi-layer structure with adjustable shape recovery speed, and multi-layer structure prepared by photo-curing 4D printing

A method for photo-curing four-dimensional (4D) printing of a multi-layer structure with an adjustable shape recovery speed, comprising the following steps:

• printing a slow layer, wherein an ultraviolet irradiation energy used during the printing of the slow layer is Islow, and a molecular chain cross-linking degree during the printing of the slow layer is Dslow;
• printing a transition layer on the slow layer, wherein an ultraviolet irradiation energy used during the printing of the transition layer gradiently decreases in a thickness direction of the printing;
• printing a fast layer on the transition layer, wherein an ultraviolet irradiation energy used during the printing of the fast layer is Ifast;
• a molecular chain cross-linking degree during the printing of the fast layer is Dfast;
• Islow>Ifast, and Dslow>Dfast;
• and the fast layer comprises a nanocarbon light-absorbing material to absorb ultraviolet light to reduce an exposure energy of incident light;
• and
• printing the slow layer on the fast layer.