No abstract

Origami-based designs refer to the application of the ancient art of origami to solve engineering problems of different nature. Despite being implemented at dimensions that range from the nano to the meter scale, origami-based designs are always defined by the laws that govern their geometrical properties at any scale. It is thus not surprising to notice that the study of their applications has become of cross-disciplinary interest. This article aims to review recent origami-based applications in engineering, design methods and tools, with a focus on research outcomes from 2015 to 2020. First, an introduction to origami history, mathematical background and terminology is given. Origami-based applications in engineering are reviewed largely in the following fields: biomedical engineering, architecture, robotics, space structures, biomimetic engineering, fold-cores, and metamaterials. Second, design methods, design tools, and related manufacturing constraints are discussed. Finally, the article concludes with open questions and future challenges.

Herein, magnetic wood was successfully prepared by in situ synthesizing Fe 3 O 4 in wood, through coprecipitation chemical interactions. A facile impregnation method, vacuum impregnation followed by pressure impregnation, was introduced to transport the adequate amount of ferric salt precursor and to further shorten the required production cycle. It was demonstrated that the obtained products exhibited outstanding microwave-absorbing properties. The best electromagnetic interference (EMI) absorbing properties could reach −64.26 dB at 14.36 GHz with the matching thickness of only 2.25 mm and broad absorbing bandwidth (| RL| > 10 dB) of 5.20 GHz covering 12.80−18.00 GHz. The subsequent thorough investigations proved that this good shielding property was due to the distinctive selfassembling morphology of Fe 3 O 4 formed in the inner surface of the lumen walls in wood, which permitted optimal impedance matching, the strongest dielectric loss, optimal magnetic loss, and an interconnected conductive network for electron hopping and migrating. This synthetic process for magnetic wood is quite facile, and the resulted EMI absorbing properties are tunable by the concentrations of the iron precursor solutions and the thickness values. This kind of synthetic magnetic wood can be potentially used as light-weight, flexible, and strong absorbing performance shielding materials for construction, furniture, decoration, and packing.

Peripheral nerve injury (PNI), causing loss of sensory and motor function, is a complex and challenging disease in the clinic due to the restricted regeneration capacity. Nerve guidance conduits (NGCs) have become a promising substitute for peripheral nerve regeneration, but their efficacy is often limited. Here, inspired by the physiological structures of peripheral nerves, we present a conductive topological scaffold for nerve repair by modifying Morpho butterfly wing with reduced graphene oxide (rGO) nanosheets and methacrylated gelatin (GelMA) hydrogel encapsulated brain-derived neurotrophic factor (BDNF). Benefiting from the biocompatibility of GelMA hydrogel, the conductivity of rGO and parallel nanoridge structures of wing scales, PC12 cells, and neural stem cells grown on the modified wing have an increased neurite length with guided cellular orientation. In addition, the NGCs are successfully obtained by manually rolling up the scaffolds and exhibited great performance in repairing 10 mm sciatic nerve defects in rats, and we believe that the NGCs can be applied in reparing longer nerve defects in the future by further optimization. We also demonstrate the feasibility of electrically conductive NGCs based on the rGO/BDNF/GelMA-integrated Morpho butterfly wing as functional nerve regeneration conduits, which may have potential value for application in repairing peripheral nerve injuries.

No abstract