Rotational Co-extrusion 4D printing of heterogeneous filaments to enable sophisticated shape morphing

Multi-material additive manufacturing has recently flourished due to its capability to fully exploit the potential of 3D printing for constructing sophisticated heterogeneous material structures. However, producing filaments with tunable internal heterogeneous architecture is difficult in current extrusion-based 3D printing processes. Herein, a novel rotational co-extrusion 3D printing method is proposed that can enable the programmable material configuration of extruded filaments, which is achieved by using a rotatable Y-shape nozzle. By coordinating the rotation and movement of the extrusion nozzle, as well as the air pressure, the material conformation of extruded filaments can be controlled. This strategy can achieve a variety of spatial distribution configurations of heterogeneous materials. In addition, different patterns with customized surface textures have been produced. Furthermore, the 4D printed heterogeneous hydrogels with differential stimuli-responsive properties are demonstrated to generate well-regulated shape-morphing as pre-designed. This method provides an intrinsic ability for 3D printing to construct heterogeneous-filament structures, which have potential applications in the fields of reconfigurable structural materials, tunable meta-materials, tissue engineering, soft robots, etc.