Programmable and multistable metamaterials made of precisely tailored bistable cells

This study proposes a systematic inverse design framework for constructing multistable mechanical metamaterials with programmable gradients. Herein, we designed the tailored bistable cells with precisely controlled maximum instability forces through the topology optimization approach. Then, the designed bistable structures were programmed to construct the multistable mechanical metamaterials with different target gradient snapping sequences and deformation models. Consequently, the simulation and experimental results showed the feasibility of the design method, which successfully produced two- and three-dimensional mechanical metamaterial structures with different functions. Finally, we verified the expected deformation sequences and multistable behaviors of mechanical metamaterials by testing the designed specimens prepared via additive manufacturing. Overall, our findings show that the proposed design strategy offers a new paradigm for developing precisely tailored and programmable mechanical metamaterials.