Bistability of architected metamaterials enabled by antisymmetric bending

Bistable architected metamaterials exploit geometric instability to enable snap-through switching, programmable mechanical response, and reconfigurable deformation, making them attractive for soft robotics, deployable structures, and shape-morphing systems. Nevertheless, many existing bistable architected metamaterials rely on axial compression, tension, or torsion to trigger bistability. Stable state transformation triggered by an externally applied bending moment or imposed rotation remains less developed despite its natural compatibility with flexure-dominated structural systems. In addition, conventional planar bistable curved-beam unit cells provide limited geometric routes for coordinating bistability and load-bearing capacity. Here, we introduce an Antisymmetric-Bending-Enabled Architected Metamaterial (A-BEAM), a modular unit cell consisting of two three-dimensional curved shells connected by a stiff I-shaped frame. Each unit cell enables local transformation between stable states, allowing the collective response of assembled units to be translated into programmable planar and spatial reconfiguration. Stable state transformation is achieved through the antisymmetric bending deformation of the curved shells. The curved-shell geometry also provides a widthwise geometric degree of freedom for coordinating bistability and load-bearing capacity. To understand and predict this behavior, we develop a physically interpretable strip-discretized analytical model, in which the curved-shell response is constructed from the dominant bending contribution arising from strip deflection, together with strip torsion and inter-strip interactions. Experiments on 3D-printed specimens, together with finite element analysis, were used to evaluate the characteristic mechanical properties and validate the analytical model. Across the parametric FEA design space, the analytical model captures the key response features with mean relative errors of 4.9% and 9.5% for the peak moment and bistable ratio, respectively. A parametric study based on 1225 finite element simulations further shows how the mechanical behavior is primarily determined by two dimensionless geometric parameters. Compact predictive formulas are established for the peak moment and bistable ratio. Overall, the A-BEAM provides a structural strategy for developing bistable architected materials and reconfigurable systems that operate under bending, with tunable bistability and programmable shape transformation.