4D printing is a novel concept that emerges in recent years, benefiting from the rapid development of advanced 3D printing technologies and active materials. In 4D printing, upon external stimuli on demand, a 3D printed part can change its shapes as a function of time, which becomes the 4th dimension of the shape forming process. 4D printing offers the advantages of forming complicated 3D shapes from low dimensional structures, saving printing materials and printing times, etc. These make it suitable for applications including morphing structures, sensors, actuators, and soft robots.
In this talk, we start with the concept of 4D printing. We then introduce several different approaches to achieve 4D printing, including using hydrogel based 3D printing method where the hydrogel swelling behavior is coupled with structure anisotropy, printed active composites that utilize multimaterial 3D printing, and internal stress based approach where the residual stress generated in 3D printing process is used to promote shape change. Finally, we discuss the challenge and future directions for 4D printing.
