Abstract
Developments in multi -material polymer printing have kickstarted the advancements in 4D printing of polymers. Currently, there are many different methods to produce shape memory polymers via 3D printing techniques. However, most of them are one-way shape memory, which means that they cannot be used reversibly. The new direction of development in 4D printing is achieving reversibility. This review will present the different 3D printing techniques used to produce one-way shape memory polymers (SMPs) and reversible SMPs.