4D printing of multiple shape memory polymer and nanocomposites with biocompatible, programmable and selectively actuated properties
4D printing of shape memory polymers (SMPs) endows the 3D printed structures with tunable shape-changing behavior and functionalities that opens up new avenues towards intelligent devices. Multiple-SMPs, specially, could memorize more than two shapes that have greatly extended the performance of 4D printed structures. However, the actuation to trigger the shape change of 4D printed multiple-SMPs is usually by direct heating to different temperatures. It hasn’t brought the full superiority of the programmability of multiple-SMPs with distinct responsive regions that could be sequentially and selectively actuated by various stimuli. Besides, the functionality of multi-material based additive manufacturing is another area that has not been fully developed. Herein, 4D printing of poly (D,L-lactide-co-trimethylene carbonate) (PLMC)/poly (trimethylene carbonate) (PTMC)/Fe3O4 multi-material with multiple shape-changing capabilities under sequential stimuli of remotely magnetic field and heat was achieved. At first, we optimized the composition of pure SMP to fine tune the multiple shape memory effect and quantitatively characterized the shape recovery by stepwise heating. Then with the addition of Fe3O4 nanoparticles, the multi-material distribution of 4D printed structure consisting of multiple-SMP and its nanocomposites was designed. The integration of multi-material additive manufacturing with multiple shape memory effect extends the shape transformation to quintuple complex shapes with accurate and local controllability under selective multi-stimuli. The 4D printed multiple-SMP and its nanocomposites with simultaneously thermo- and magnetic- responsive shape-changing capability also demonstrated excellent biocompatibility. This work thus offers a feasible and robust approach for 4D printing of multi-functional devices for broad applications in entertainment, robotics, biomedical field and beyond.