Emerging 4D printing strategies for on-demand local actuation & micro printing of soft materials

Responsive functional composites comprise of materials that can react to environmental stimuli and remodel their shapes. 4D printing and integrating active materials render enormous design flexibility to the printed structures. The 4D printing technology has witnessed significant progress in recent years; however, stimulation method and mechanism, ingenious compound, printing resolution, and scale are specific warrant further research and development. This review extensively describes recent studies on indirect heating (electrical, magnetic, and light) methods for triggering shape memory polymers and liquid crystal elastomers. It also discusses the miniaturization printing of active compounds at the submicron or nano level, which has initiated the era of mini self-robot, miniature medical equipment, and self-assembly structures. A further section is on robust construct models, numerical simulation, and advanced tools, i.e., ML, AI FE, for efficient verdict applicable designs to accomplish a target shape change. In addition, this review highlights the potential applications such as soft robotics, tissue engineering, drug delivery, and 4DP structures as absorbers.