Novel 2D metamaterials with negative Poisson's ratio and negative thermal expansion

It is known that metamaterials with negative Poisson's ratio (NPR) can be designed to possess negative thermal expansion (NTE) property. However, it is uncommon to use NTE structures to obtain NPR behavior. In this paper, based on a typical NTE unit structure, two novel meta-structures with auxetic behavior are proposed, which are demonstrated by the micro-scale mechanical experiments and numerical simulations. By changing the angle of the structure, the Poisson's ratio of the structures could be positive, zero and negative. The extreme negative Poisson's ratio of the structures is about -0.94. Moreover, the thermal expansion of the novel 2D structures can also be designed and modulated to be positive, zero and negative. This concept of building 2D metamaterials with NPR in this study would open up new avenues to understand and design metamaterials with NPR and NTE for potential engineering applications, such as smart sensors and electronic components.