Mechanical metamaterials have enabled exotic and desirable mechanical properties that are inaccessible with conventional materials owing to their properly engineered repeating microstructures. Origami, which transforms 2D materials into complex 3D structures, is able to provide a geometric design approach independent of scale and material, and hence offers a promising platform for the design of metamaterials. Thus, our laboratory focuses on the design of metamaterials depending on the multilayer origami structures.

1 Origami-inspired mechanical metamaterials

A systematic design theory for origami-inspired mechanical metamaterial was developed. This theory made a full use of the inherent folding behavior of origami patterns, and generated large-scale metamaterials through 3D tessellation. Based on this theory, a series of mechanical metamaterials with 3D negative Poisson’s ratio and tunable stiffness were proposed. These mechanical properties of the metamaterials can be programmed by the geometric design parameters of the origami patterns, and by controlling the material properties of the creases and facets of the origami structures.

Origami-based mechanical metamaterials with negative Poison’s ratio in three-dimensions and tunable stiffness

2 Graded mechanical metamaterials

A graded mechanical metamaterial, based on the Miura-ori folding pattern, was created to adapt to non-uniform environments. The geometric parameters of this metamaterial was varied using kinematic analysis to create both rigid foldable and self-locking stages in the configuration. This property gives the graded metamaterial an opportunity to achieve graded stiffness when subjected to quasi-static in-plane or out-of-plane compression, and superior energy absorption capability to uniform tessellating repeat units. Meanwhile, these mechanical responses can be tuned by changing the underlying geometric design.

The out-of-plane uniform and graded mechanical metamaterials