Shape memory polymers (SMPs) and their composites (SMPCs) are smart materials that can be stably deformed and then return to their original shape under external stimulation, thus having a memory of their shape. Three-dimensional (3D) printing is an advanced technology for fabricating products using a digital software tool. Four-dimensional (4D) printing is a new generation of additive manufacturing technology that combines shape memory materials and 3D printing technology. Currently, 4D-printed SMPs and SMPCs are gaining considerable research attention and are finding use in various fields, including biomedical science. This review introduces SMPs, SMPCs, and 4D printing technologies, highlighting several special 4D-printed structures. It summarizes the recent research progress of 4D-printed SMPs and SMPCs in various fields, with particular emphasis on biomedical applications. Additionally, it presents an overview of the challenges and development prospects of 4D-printed SMPs and SMPCs and provides a preliminary discussion and useful reference for the research and application of 4D-printed SMPs and SMPCs.

Achieving high thermal conductivity in rigid liquid crystal-based units without compromising their superflexibility is challenging. A strategy tacking synergistic enhancement of hydrogen bonds and liquid crystal main chains to form a multidimensional cross-linking network structure is proposed. An intrinsically thermally conductive shape memory polymers with ultra-high strength, ultra-high toughness, low-temperature resistance and wear resistance were obtained. It can lift up to 10,000 times its own weight (10 kg), has bending radius of even 0.99mm and remains super-flexibility at -190°C, achieving an unprecedented damage tolerance for thermosetting resins and laying the foundation for its foldable. We regulate the spherical crystal size by the solvent-induced self-assembly method, achieving intrinsic thermal conductivity of 1.2 W/m·K. We took inspiration from the bionic structure of earwig wings combined with crease vanishing function to apply high-aspect-ratio deployment structures in aerospace, achieving compatibility between deformation and load bearing.