Rod Origami (RodOri) Spring Metamaterials for Tunable Vibration Control via Tailored Structural Instabilities.

Modern engineering systems increasingly operate under varying vibrational environments, necessitating structural components capable of adapting their dynamic responses on demand. While springs have long served as the core of vibration control systems, their fixed stiffness fundamentally limits adaptability. Here, we introduce reconfigurable springs based on the structural instability of rod origami (RodOri), constructed from pre-stressed, naturally curved elastic rods. By tailoring the natural curvature and cross-sectional aspect ratio of the constituent rods, both the onset of snap-through buckling and the post-buckling response of individual RodOri springs can be systematically programmed. Leveraging this geometric programmability, we establish a system-level design principle in which multiple RodOri springs of identical length but distinct buckling behaviors are assembled into a multistable metamaterial. Differences in snapping displacements enable stepwise structural reconfiguration via sequential snap-through transitions, while variations in post-snapping stiffness govern the mechanical response of each configuration. This hierarchical tunability enables both broad and fine control of resonance frequencies and dynamic responses across stable states. Numerical simulations and experiments demonstrate on-demand modulation of vibration amplification, isolation, and impact mitigation within a single metamaterial, establishing RodOri springs as reconfigurable, programmable building blocks for adaptive structural and wave dynamics.