Shape-Memory Balloon Structures by Pneumatic Multi-material 4D Printing

4D printing is an attractive approach for manufacturing structures that can adopt new shapes or functionalities after printing. However, 4D printing methods and materials that can be used to achieve structures with complex shapes and excellent mechanical properties simultaneously are still lacking. Here, a novel 4D printing is developed where multi-material digital light process 3D printing of shape memory polymers (SMPs) fabricates a structure that is later transformed into a complex 3D shape with robust mechanical properties by pneumatic manipulation. In this method, the shape change is controlled by the spatial distributions of SMPs, which is designed by finite element analysis. Experimental investigations are carried out to print various structured balloons with predefined intricate shapes, including a structure in dog-like shape and a surface with the human face contour. These structures are also endowed with robust mechanical stiffness and lightweight features, which allow this new 4D printing approach for potential applications in biomedical devices, reconfigurable structures, and metamaterials.