A novel polar mechanical metamaterial with dual deformation characteristics

Polarity refers to the phenomenon of an object exhibiting opposite intrinsic properties in opposing directions, which plays a fundamental role in various fields including mechanical diodes, mechanical logic gates, and shock protection. This paper proposes a new mechanical metamaterial with polar and dual deformation characteristics based on a fishbone-like structure to enable a given surface structure to be hard while its opposite side is soft, while also enabling the task of adapting to different load levels on the soft side. The mechanical metamaterial displays double-stress platforms and exhibits a significant difference in mechanical response when loaded on opposite sides. Through numerical simulations, the polarity characteristic spectrum of the mechanical metamaterial is identified. The stress platform with a soft boundary predicted using Euler's instability theory was verified through both numerical simulation and experimentation. The dimensionless parameters for load differences are defined to evaluate the polar characteristics of polar mechanical metamaterials, and design guidelines are provided for achieving significant polar characteristics of polar mechanical metamaterials by discussing the influence of geometrical parameters. The proposed polar mechanical metamaterial introduces a novel design concept applicable to signal transmission, isolation, and energy absorption for different load levels.