Flexible and robust exoskeletons and armors are crucial in fields such as intelligent manufacturing, military applications, healthcare, deep sea exploration and rescue operations. Traditional exoskeletons assembled by metal parts often struggle to achieve both lightweight and flexibility. In nature, seahorses have evolved exoskeletons capable of withstanding compressive forces up to 20000 times its own weight, while retaining flexibility. Self-locking mechanism of the seahorse tail under the combination of soft tissues and hard skeleton was revealed using in-situ micro computed tomography in the current work. Inspired by these findings, a flexible exoskeleton combining soft and hard material was designed and fabricated integrally by multi-material 3D printing. Quasi-static compression tests revealed that the 3D-printed structure could endure loads of up to 351 N, which is equivalent to 3000 times its own weight, and maintain structural intactness under large compression (up to 30% deformation) and cyclic loadings. The bioinspired exoskeleton demonstrates a compression-induced self-locking mechanism, leading to stiffness increasing. This variable stiffness design substantially improves the exoskeleton's compressive resistance and energy absorption. Flexibility is further verified by multimodal deformation demonstrations. The bioinspired design of 3D printed exoskeleton can be further applied in deep sea explorations where flexibility and high pressure resistance meet together.
Fu et al. (Wed,) studied this question.