Biomimetic composite meta-stabilisers with programmable multi-directional quasi-zero stiffness and vibration isolation

This study introduces the first multidirectional quasi-zero-stiffness (QZS) meta-stabilisers that integrate bio-inspired curvilinear architectures with a sustainable polymer composite developed in this work. The QZS behaviour emerges synergistically from both structural design and nonlinear visco-hyper-elasticity of the newly developed bio-composite. Inspired by the woodpecker's tongue mechanism, the design leverages the interaction of geometry and material features to achieve exceptional damping and vibration isolation performance. The meta-stabilisers employ a Thermoplastic Polyurethane (TPU)/Polyhydroxyalkanoate (PHA) matrix reinforced with 2.5 wt% eggshell powder. It provides a bio-composite with 20 % higher tensile strength and 60 % greater energy dissipation than the unreinforced matrix. A hybrid computational framework, combining finite element modelling of nonlinear visco-hyper-elastic materials and AI-driven optimisation, enables precise control of the plateau region and constant-force output. The bio-composite generates a broad, stable plateau within 0.2–0.8 strain, perfectly matching the deformation regime of QZS structures. Experimental and numerical findings confirm stable QZS behaviour in three orthogonal directions, high vibration isolation capacity, repeatable hysteresis loops, and minimal Mullins effect over multiple cycles. In addition, the meta-stabilisers are programmable, where constant-force is tuneable between 0.5 and 220 N and displacement range between 1 and 7 mm. Under both periodic and random excitation, the meta-stabilisers achieved up to 100 % suppression of periodic vibrations and 77 % reduction under random vibrational off-road conditions. These results establish a new class of bio-inspired, sustainable, and programmable vibration control systems, offering a scalable, low-cost alternative to conventional active/passive noise/vibration/harshness solutions.