Research Progress of Mechanical Metamaterials

Owing to their unique mechanical properties compared to conventional materials, mechanical metamaterials have attracted a lot of attention. This unique and novel characteristic is closely related to the microstructure and geometry of mechanical metamaterials, rather than material composition. In addition, many special mechanical properties can also be obtained by designing and .preparing various materials and structures. At present, the development of the preparation process makes it possible to prepare materials with arbitrarily complex micron or nanostructures. In the present paper, the research progress of several mechanical metamaterials properties was reviewed, including strong-ultralight, negative Poisson's ratio, negative compressibility, negative thermal expansion, and meta-fluids. In addition, the restrictive factors of the development of mechanical composite materials were summarized, and the research key point and development directions in this field were put forward.