4D printing and its key technologies

4D printing can be defined as the evolution of 3D printing structure in terms of shape, performance and function. It has time dependence, printer independence and predictability, and its smart dynamic performance creates promising capabilities and broad potential applications. On the basis of a brief review of the status of 4D printing at home and abroad, the concept and components of 4D printing were given firstly. Then the 4D printing was classified from the dimension of printing structure shape change. Furthermore, the key technologies such as printing materials, incentive mechanism and mathematical modeling method in 4D printing elements were analyzed. Finally, it was pointed out that the development direction of 4D printing technology is to combine intelligent materials with 3D printing, simplify the manufacture of complex structures, and realize the automation, intellectualization and personalization applications in special service environments and fields such as aerospace, deep sea and precise medical treatment by using its unique characteristics of self-assembly, self-adaption and self-repairing.