# Design Methodology and Application Dynamics of Compact Quasi-Zero Stiffness Isolators
## 4 Summary and Outlook
### Outlook  
1. Currently, most of the vibration isolation devices focus on the suppression in the vertical direction, but in practical engineering, such as the suppression of seismic loads in high-risk buildings, the vibration and noise reduction design of ships coupled with waves and engine vibration, and the vibration design of airplanes under airflow disturbances and landing impacts, the multidirectional and complex excitations cannot be avoided. Therefore, the multi-degree-of-freedom QZS system has a broader application potential. However, there is a lack of systematic modeling methods for key issues such as nonlinear stiffness matching and decoupling of energy transfer paths under multidirectional excitation. Future research is urgently needed to establish a multidirectional collaborative design theory that integrates the negative stiffness regulation mechanism and, at the same time, develops optimization algorithms that can take into account the coordination of axial load-carrying capacity and multidirectional stiffness to cope with the complex effects of multidimensional excitations in practical engineering.
2. The combination of metamaterials and biomimetic design provides more freedom in the design of QZS isolation, especially in improving structural durability and saving space. In the future, the performance and adaptability of vibration isolators can be further enhanced through the development of new tunable composite materials and bionic structures, especially for applications in extreme operating environments.
3. Magnetic compact design mainly focuses on the optimization of space structure and the improvement of magnetic density. In general, permanent magnets can provide greater magnetic field strength than electromagnetic coils, but permanent magnets are fragile and demagnetized at high temperatures, which limits the application of permanent magnet coils in strong shock and high-temperature environments. Electromagnetic coils are difficult to develop a large enough magnetic stiffness, which requires optimization in the magnetic circuit design.
4. Due to the significant differences in different application scenarios, the design requirements of QZS isolation show diverse characteristics. Compact structural design, strong load-bearing capacity, flexible adjustability, sufficient travel, and effective isolation of vibrations of different amplitudes are all key factors to be considered in the design process. Therefore, the development of QZS isolation with multiple characteristics has become a core direction for future research. By integrating the above characteristics, it is expected to break through the limitations of the existing vibration isolation technology, better meet the increasingly complex and demanding vibration isolation needs in various fields, and promote the wide application and in-depth development of vibration isolation technology in engineering practice.  
Conceptualization, Y.Z. and Q.Y; methodology, Q.Y.; validation, Q.Y.; formal analysis, Q.Y.; investigation, S.L.; writing--original draft preparation, Y.Z.; writing review and editing, S.L.; supervision, K.C.; funding acquisition, K.C. All authors have read and agreed to the published version of the manuscript.  
Research on these results was supported by the National Natural Science Foundation of China (NSFC) under grant number 52471354.  
Not applicable.  
There is no other support that is not covered.