Zhang Hang, Wu Jun, Fang Daining, Zhang Yihui
AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, P.R. China.
Center for Flexible Electronics Technology, Tsinghua University, Beijing 100084, P.R. China.
Sci Adv. 2021 Feb 24;7(9). doi: 10.1126/sciadv.abf1966. Print 2021 Feb.
Multistable mechanical metamaterials are artificial materials whose microarchitectures offer more than two different stable configurations. Existing multistable mechanical metamaterials mainly rely on origami/kirigami-inspired designs, snap-through instability, and microstructured soft mechanisms, with mostly bistable fundamental unit cells. Scalable, tristable structural elements that can be built up to form mechanical metamaterials with an extremely large number of programmable stable configurations remains illusive. Here, we harness the elastic tensile/compressive asymmetry of kirigami microstructures to design a class of scalable X-shaped tristable structures. Using these structure as building block elements, hierarchical mechanical metamaterials with one-dimensional (1D) cylindrical geometries, 2D square lattices, and 3D cubic/octahedral lattices are designed and demonstrated, with capabilities of torsional multistability or independent controlled multidirectional multistability. The number of stable states increases exponentially with the cell number of mechanical metamaterials. The versatile multistability and structural diversity allow demonstrative applications in mechanical ternary logic operators and amplitude modulators with unusual functionalities.
多稳态机械超材料是一种人工材料，其微观结构具有两种以上不同的稳定构型。现有的多稳态机械超材料主要依赖于受折纸/剪纸启发的设计、突变失稳和微结构软机制，其基本单元大多为双稳态。可扩展的三稳态结构元件，能够构建出具有极大量可编程稳定构型的机械超材料，目前仍然难以实现。在此，我们利用剪纸微结构的弹性拉伸/压缩不对称性，设计了一类可扩展的X形三稳态结构。以这些结构作为构建块元件，设计并展示了具有一维（1D）圆柱几何形状、二维方形晶格和三维立方/八面体晶格的分层机械超材料，它们具有扭转多稳态或独立控制的多向多稳态能力。稳定状态的数量随机械超材料的单元数量呈指数增加。这种通用的多稳态和结构多样性使其在具有特殊功能的机械三元逻辑运算符和幅度调制器中具有示范性应用。
