High-Throughput Experiments and Reliability Assessment of 3-D Printed Bistable Mechanical Metamaterials connected in series

Abstract

Bistable mechanical metamaterials, structures with two mechanically stable states, offer promising potential for deployable, energy-efficient, and adaptive systems in aerospace, robotics, and biomedical engineering. However, their design optimization remains challenging due to geometric nonlinearity, sensitivity to boundary conditions, and manufacturing inconsistencies. Moreover, how these materials interact and perform as a system, whether configured in series or in parallel, is still not well understood. This work introduces a comprehensive, high-throughput framework for the design, fabrication, testing, and optimization of 3D-printed bistable metamaterials, aimed at studying the behavior of them as a system and enhancing performance and reliability. A horizontal experimental setup was developed to rapidly characterize multiple bistable unit cells connected in series under uniaxial tension and compression, significantly reducing the time and effort required for mechanical testing. Structures were fabricated using PLA and TPU and designed with varying ligament geometries, Q values, and unit cell architectures to systematically explore the parameters influencing bistability. High-throughput testing revealed key insights into snap-through forces, hysteresis, and the influence of gravity, friction, and alignment on load distribution. Notably, increasing TPU beam thickness shifted the bistability threshold, while frictional inconsistencies across the test rail introduced variability, especially in larger assemblies. Finite element simulations in Abaqus complemented the experiments, accurately capturing nonlinear deformation and snap-through behavior. The simulations enabled deeper analysis of stress localization, energy barriers, and bistability windows, aligning well with experimental trends and informing design sensitivity. Together, the experimental and numerical findings provide a scalable strategy for rapid bistable metamaterial evaluation, offering actionable design guidelines to improve consistency, reliability, and performance in adaptive structural applications.