Applications of four-dimensional printing in emerging directions:Review and prospects

Four-dimensional(4 D) printing technology is an extension of three-dimensional(3 D) printing technology that enables a 3 D-printed static structure to dynamically change its shape with time. Therefore, the resulting structure can undergo self-folding/unfolding assisted by some stimuli. This technology has made much initial progress in many industrial fields. Aiming to investigate the in-depth application value of4 D printing, this study reviews the recent research and application breakthroughs of 4 D printing in several emerging directions, including the simulation of plant and animal behaviors, smart tissue scaffolds and biomedical devices, food printing, digitalization of industrial art design, renewable energy, intelligent communication, soft electronics and robots, vehicle optimization, textile customization, and flexible machinery and mechanical structure. Based on the analyses of specific cases and processes, we present the current obstacles to large-scale applications and the future prospects.