Tensegrity-Inspired Pre-Stress Control for Programmable Multistability and Stiffness in Mechanical Metamaterials

Abstract

Mechanical metamaterials have considerable application potential, but are often limited to single applications owing to material and manufacturing constraints. To achieve a “single structure, multiple applications” goal, this study presents a multifunctional metamaterial structure. The metamaterial cells gain significant deformation and recovery abilities by incorporating the concept of a tensegrity structure to balance flexibility and rigidity and using a rigid-flexible fabrication process. Inspired by cat-tongue barbs and Hooke's law, an innovative pre-stress programming structure is designed for integrated fabrication, enabling multilevel pre-stress control for each cell. This programmable stress allows the twin-cell array to transition in situ from monostable to bistable states and provides multilevel critical-force functions for bistable states. After assembling a nine-cell array, the structure offers a wide range of adjustable stiffness levels, enabling soft-rigid transitions and varied force-displacement responses without the need for additional tools. It also allows controlled collapse ratios and deformation through stiffness control. Additionally, the nine-cell array features isotropy with a Poisson ratio of v = −1 and clear indentation resistance. This approach is promising for applications such as adjustable energy dissipators, automotive equipment, and passive safety.