Engineering bistability in mechanical metamaterials: A framework inspired by cardiac applications

We present a design methodology for mechanical metamaterials featuring coupled bistability and tailored kinematic responses. Motivated by potential applications in cardiac assist devices, we aim to create structures capable of switching between stable configurations while undergoing complex, multidirectional motions (such as compression coupled with torsion) triggered by simple loading conditions. The study begins with a fundamental analysis of the three-hinged symmetric arch, investigating the influence of rotational stiffness on its snap-through behaviour using both truss and beam formulations. Building on this archetype, we introduce and analyse two planar unit cell concepts: superimposed and integrated architectures. These 2D designs are subsequently extended into a 3D metamaterial framework through a geometric transformation that incorporates circumferential curvature. The resulting 3D architecture preserves the in-plane connectivity of the unit cells while achieving the desired coupled kinematic response, offering a robust strategy for engineering programmable mechanical behaviours in biomedical and soft robotic systems.