In this review, the state-of-the-art efforts in integrating the time-dependent behaviour of stimulus-responsive materials in 4D printing will be discussed. In addition, we have demonstrated the significance of 4D printing in biomedical applications, in which “time” has been incorporated into the conventional concept of 3D printing as the 4th dimension. As such, 4D printing differentiates and evolves from 3D printing using stimulus-responsive materials which can actively respond to external stimuli and more sophisticated “hardware”-printer which can achieve multi-printing via mathematical-predicted designs that are programmed to consider the transformation of 3D constructs over time. The emphasize will be on the interactions between various types of stimuli with the associated stimulus-responsive materials, followed by technical considerations as well as outlook for future discoveries.

https://www.sciencedirect.com/science/article/pii/S1742706119303204?via%3Dihub