Quasi-Zero-Stiffness Vibration Isolation: A Comprehensive Review of Design Principles and Engineering Applications

Quasi-zero-stiffness (QZS) vibration isolation technology achieves high-static-low-dynamic-stiffness (HSLDS) and thereby resolves the fundamental trade-off between load-bearing capacity and isolation frequency inherent to conventional linear isolators. This paper systematically reviews recent advances in QZS isolators with a focus on literature published in the last five years. Systems are classified by degrees of freedom (DOF) into single-DOF (SDOF) and multi-DOF (MDOF) configurations. For SDOF systems, seven principal design archetypes are discussed: multi-spring, spring-linkage, cam-roller, magnetic, biomimetic, origami-inspired, and metamaterial-based structures. Beyond the classic approach of assembling positive-stiffness and negative-stiffness components, emerging design strategies such as topology optimisation and meta-structure concepts are examined. Adjustable and load-adaptive designs that preserve stable high-performance isolation under variable static loading receive dedicated emphasis. As QZS isolators are inherently nonlinear systems, their complex dynamic behaviours including sub-harmonic and super-harmonic resonances, bifurcations and chaos are analysed. For MDOF systems, progress in 2-DOF, 3-DOF and 6-DOF platforms is summarised with attention to multi-dimensional vibration decoupling and coordinated stiffness regulation for high-precision equipment. Finally, engineering applications of QZS technology are highlighted covering vehicle seat isolation, aerospace systems, vibration energy harvesting, bridge seismic protection and precision manufacturing, demonstrating substantial practical utility. • Comprehensive review of quasi-zero-stiffness vibration isolators. • Covers SDOF designs: multi-spring, linkage, cam, magnetic, bionic, origami, metamaterial. • Summarizes MDOF isolators for 2-, 3-, 6-DOF vibration control. • Highlights adjustable and load-adaptive QZS for variable loads. • Discusses engineering applications in seats, aerospace, energy harvesting, bridges.