Mechanical properties of hierarchical anti-tetrachiral metastructures

Chiral structures consisting of circular ring nodes and tangentially connected ligaments are engineered systems that exhibit excellent flexibility, vibration attenuation, impact resistance performance, etc. In this paper, we proposed an innovative hierarchical anti-tetrachiral structures based on the auxetic deformation behaviors of anti-tetrachiral unit cell at different structural hierarchical levels. The in-plane mechanical properties of hierarchical anti-tetrachiral metastructures are deduced from strain energy analysis, experimental and finite element analysis (FEA) comparisons are employed for verification. The in-plane mechanical properties of hierarchical anti-tetrachiral metastructures can be remarkably enhanced and manipulated through combining the auxetic deformation behaviors of chiral structures and the mechanical benefits of structural hierarchy, and its tunable mechanical properties can be designed within very large range of modulus and Poisson's ratio value. Finally, an innovative hierarchical anti-tetrachiral stent is proposed, and the interaction between stent and artery vessel are studied, demonstrating the promising industrial application potential of hierarchical chiral metastructures. The proposed chiral geometry represents a new family of chiral hierarchical structures, and the extent of auxeticity and its in-plane mechanical properties can be tuned through manipulating node ring size and shape, length and thickness, and the hierarchy level, thus achieving desired extreme mechanical properties. It is believed that this work can greatly expand the potential applications of chiral metamaterials in conformable and stretchable electronics, biomedical devices, electronic skin, stents, and reconfigurable soft robotics, etc.