Current status and future outlook of 4D printing of polymers and composites-A prospective

摘要

• Provides a comprehensive review of the advancements in 4D printing of polymers and composites, integrating time-responsive behavior into additive manufacturing. • Explores the principles, mechanisms, and key materials such as shape memory polymers, hydrogels, liquid crystal elastomers, and self-healing polymers. • Showcases diverse applications in biomedical engineering, aerospace, automotive, electronics, and soft robotics, emphasizing adaptive and self-assembling structures. • Identifies challenges in material limitations, computational complexities, and industrial scalability while proposing future research directions for optimization and broader adoption. Four-dimensional (4D) printing represents a transformative advancement in additive manufacturing, integrating time-responsive behavior into traditionally static three-dimensional (3D) printed structures. This emerging technology leverages stimuli-responsive materials such as shape memory polymers, hydrogels, liquid crystal elastomers, and smart composites that undergo controlled and reversible transformations when exposed to external triggers, including temperature, humidity, light, and magnetic or electric fields. Over the past decade, substantial research efforts have been directed toward refining material properties, optimizing printing parameters, and expanding the applicability of 4D printing across high-impact industries. This review provides a comprehensive analysis of the fundamental principles, material innovations, and emerging applications of 4D printing in sectors such as biomedical engineering, aerospace, automotive, and soft robotics. Particular emphasis is placed on programmable structures, morphing mechanisms, and self-actuating materials, which drive the next generation of dynamic manufacturing. Additionally, this study critically examines existing challenges, including material limitations, scalability issues, and computational complexities that hinder widespread industrial adoption. By identifying these constraints and proposing future research directions, this review aims to accelerate the transition of 4D printing from a novel laboratory innovation to a fully integrated industrial-scale technology.