Over many millions of years of evolution, nature has given birth to innumerable biological materials which serve either as the skeletons of the organisms or as offensive or defensive weapons. Although these natural structural materials are derived from comparatively sterile natural components, such as ductile biopolymers and fragile minerals, they frequently display astonishing mechanical properties because of their extremely ordered hierarchical structures and advanced interfacial design. Thus, they are always the key object for scientists to probe and imitate aiming to produce advanced artificial structural materials.
Using microstructural observation, researchers can find that a number of biological materials, including fish scale, crab claw, and bone, all have characteristic twisted plywood structure that comprises an extremely ordered arrangement of micro/nanoscale fiber lamellas. They are structurally advanced natural fiber reinforced composites and repeatedly display superior damage tolerance that is immediately needed but difficult to be attained for engineering structural materials.
Thus, completely imitating this kind of natural hierarchical structure and interfacial design, by using artificial synthetic and copious one-dimensional micro/nanoscale fibers as building blocks, is likely to yield high-performance new-style artificial structural materials that are anticipated to surpass current engineering structural materials. However, because of the lack of micro/nanoscale assembly technology, particularly the lack of means to efficiently incorporate 1D micro/nanoscale structural units into macroscopic bulk form, imitating natural fiber reinforced composites has always been a huge challenge, and there has hardly been any reported thus far.
In reaction to this challenge, lately, inspired by the micro/nanoscale twisted plywood structure of the natural Arapaima Giga scale armor (a-d), for the first time, the biomimetic research team led by Professor Shu-Hong Yu from the University of Science and Technology of China (USTC) suggested a high-efficient bottom-up 'brushing-and-laminating' assembly strategy (e-f) with the biocompatible micro/nanofibers as structural units, successfully fabricated 3D bulk biomimetic twisted plywood structural materials (g).
Through hierarchically regulating the fiber alignment in the biopolymer matrix, the mechanical properties of ensuing materials can be exactly modulated. It was discovered that the acquired artificial materials highly replicate the multiscale structure and toughening mechanisms of their natural counterparts, realizing outstanding mechanical properties far surpassing fundamental structural components and can be comparable with those of natural bone and a number of other natural and artificial materials. More notably, the projected assembly strategy is eco-friendly, programmed, and scalable, and can be effortlessly extended to other materials systems. Thus, it offers a new technological space for engineering more advanced biomimetic fiber reinforced structural materials (particularly armor protection materials).