3D printed hierarchical structures for 4D shape transformation

W. Jo, H.J. Lee, M-W. Moon
Korea Institute of Science and Technology,
Korea

Keywords: 3D printing, 4D printing, FDM, hierarchical structure

Summary:

FDM 3D printing is regarded as a promising manufacturing technique for fabrication of complicated 3D objects in a cost-effective and simple manner1. Although significant progress has been made in the improvement of the FDM printing, controlling surface morphology has been limited yet. In this study, we suggest a scalable approach for the production of large-scale 3D hierarchical structures consisting of complex defined 3D curvature and wavy features with FDM printing technology. The important aspect of this method is the exploitation of filament buckling through enough stand-off distance and the off-centered nozzle hole driven bending instability during the 3D printing. By combination of two factors, the hierarchical 3D structures could be fabricated along with the high specific surface area and large pore volume. The improved large structural variation stimulated more attachment of TiO2 nanoparticles, which increased in contact interface and rapid mass transportation under UV irradiation. In addition, controlling of printing speed resulted in the creation of periodic microstructured patterns with different frequency. The unique patterns could apply to fabricate 4D printing structures with shape memory polymeric filaments. The 4D printing behavior was investigated by spontaneous pattern transformation of the printed shape memory polymers under thermal stimuli. This method was significantly powerful and promising not only to mimic unique 3D hierarchical structure but also to utilize improved functions of more sophisticated features including large surface area or porosity. By controlling curly pattern formation and material property, various 4D structural behavior can be induced under external stimulus, which can be applied in diverse fields such as 4D transformation structure2, self-actuated structure, self-locking structure, etc.