Multistable chiral-twist metamaterials with reconfigurable deformation modes: Mechanical design, simulations and experimental demonstrations

Despite the considerable potential of multistable mechanical metamaterials in a variety of engineering disciplines, current designs principally depend on modal switching through tensile and compressive translational motion, thereby leaving rotational actuation underexplored. Here, a multistable chiral-twist metamaterial, activated by pure torsional loads, is proposed to achieve reconfigurable deformation modes through three design strategies: bi-material beams with local deformation modulation via modulus mismatch, origami beams with stable mode transitions via folding hinges, and buckling beams with bistability via residual stresses. Subsequently, theoretical models for large deformation in the beams under different boundary conditions are established based on large deflection theory, and analytical expressions are derived to predict the induced strain energy and torque at different rotation angles. Numerical simulations and experiments are conducted to verify the reconfigurable deformation mode transition behavior of the proposed chiral-twist metamaterials, which also demonstrates the effectiveness of the established theoretical models. Furthermore, hierarchical serial and parallel configurations based on origami and buckling beams are further proposed to achieve four reconfigurable stable deformation modes and energy barrier modulation in both numerical simulations and experiments. This work establishes a universal platform for engineering applications that necessitate pure rotational drive reconfigurability.