We present a route to build nacre-inspired hierarchical structures with complex three-dimensional (3D) shapes by electrically assisted 3D printing. Graphene nanoplatelet (GN) is aligned by electric field (433V/cm) during 3D printing and act as brick with polymer matrix in between as mortar. The 3D printed structures with aligned GN show reinforced mechanical property as well as 100 times reduced electrical resistance compared with random GN with the same loading. The 3D printed nacre with aligned GN (2wt%) shows lightweight (1.06g/cm3) while comparable specific toughness and strength with natural nacre. Besides, 3D printed lightweight smart armor with aligned GN can sense its own damage with a hesitated resistance change as well as protective high impact resistance. This study also highlights interesting possibilities in achieving bioinspired structures with integrated mechanical reinforcement and electrical self-sensing in biomedical, aerospace engineering as well as military and sports armors.(https://www.science.org/doi/full/10.1126/sciadv.aau9490)
