Advances in 4D Printed Shape Memory Polymers: From 3D Printing, Smart Excitation, and Response to Applications

Shape memory polymer (SMP) is a smart material that can revert from a temporary shape to a permanent shape under external stimuli, showing great potential for applications in biomedical, aerospace, and intelligent robotics fields. In recent years, with the in-depth combination of SMP and 4D printing, many breakthroughs have been made in smart manufacturing and multifunctional integrated response. Here, the authors overview the research progress of 4D printing SMP, focusing on the diverse excitation methods, intelligent response deformation modes, and applications of 4D printing SMP. Finally, they point out the problems and future development directions of 4D printing SMP in terms of the printing process, SMP modification, structural design, and multifunctional coupling design.