Design of bio-inspired quasi-zero stiffness vibration isolation metamaterials

In response to the inherent limitations of traditional linear vibration collators—whose natural frequency is constrained by static deflection, making it difficult to simultaneously achieve high load-bearing capacity and excellent low-frequency isolation performance—as well as the drawbacks of existing nonlinear collators, such as complex assembly and narrow quasi-zero-stiffness (QZS) ranges, this paper proposes a bio-inspired, multi-material, monolithic (Quasi-Zero Stiffness, QZS) immaterial for vibration isolation. The design draws inspiration from the multi-segmented “M”-shaped biological configuration observed in arthropod limbs. The proposed structure indicatively leverages the hyper elasticity of thermoplastic polyurethane (Thermoplastic Polyurethane, TPU) to generate nonlinear restoring forces, while a poly lactic acid (Polylactic Acid, PLA) framework provides rigid structural support. Through the cooperative deformation of the soft and hard materials, the quasi-zero-stiffness immaterial achieves both high load-bearing capacity and broadband performance. A finite element model was first established to conduct sensitivity analysis and parametric optimization of the QZS immaterial. An approximately optimal configuration was identified, balancing a wide effective QZS displacement range with high average load-bearing capacity. Subsequently, a multi-layer stacked architecture was developed, featuring alternating layers of “QZS soft units” and “PLA rigid beams.” Prototype samples were fabricated using dual-extrusion fused deposition modeling (Fused Deposition Modeling, FDM) 3D printing. Static compression and swept-sine excitation experiments were carried out to validate the design. Results show that the structure exhibits pronounced QZS nonlinear characteristics, with excellent agreement between experimental and simulated static responses. Compared to a single-layer configuration, the four-layer array demonstrates a significantly broader vibration isolation band gap in the low- and ultra-low-frequency ranges, effectively suppressing resonance peaks, with a minimum vibration admissibility reaching –56 dB. This study confirms the potential of bio-inspired, multi-material materialism for controlling low-frequency, small-amplitude vibrations and offers a novel, assignable, and easily manufacture solution to challenging engineering vibration isolation problems.