Mechanical properties of two-dimensional materials and their applications

The mechanical properties of materials are not only indispensable key factors in their application fields, but are also fundamentally important in terms of materials science. Since the successful isolation of graphene with an atomic thickness, two-dimensional (2D) materials have attracted enormous attention over the past decade due to their unique properties. In particular, 2D materials are of interest owing to their outstanding mechanical properties, such as high Young's modulus and strength, despite their ultrathinness and low weight in comparison to their bulk counterparts. However, studies on the mechanical properties of various 2D materials have been limited, with the exception of graphene, leaving many open questions and challenges. In this article, recent empirical and theoretical advances in studies of the mechanical properties of 2D materials and their applications are reviewed. First, mechanical characterization methods, which are widely used for ultrathin membranes, are summarized. The effects of defects on the mechanical properties of 2D materials are reviewed, including naturally (or intentionally) generated defects and chemically functionalized 2D materials. Finally, we discuss recent advances and the possibility of using 2D materials in diverse mechanical applications. The summary of the unique mechanical properties of 2D materials and their derivatives in this article would be beneficial for the study of 2D materials and their applications in lightweight, flexible, and transparent systems. (topical review)