Tuning instability in suspended monolayer 2D materials

Y Hou and JZ Zhou and ZZ He and JZ Chen and MY Zhu and HA Wu and Y Lu, NATURE COMMUNICATIONS, 15, 4033 (2024).

DOI: 10.1038/s41467-024-48345-7

Monolayer two-dimensional (2D) materials possess excellent in-plane mechanical strength yet extremely low bending stiffness, making them particularly susceptible to instability, which is anticipated to have a substantial impact on their physical functionalities such as 2D-based Micro/Nanoelectromechanical systems (M/NEMS), nanochannels, and proton transport membrane. In this work, we achieve quantitatively tuning instability in suspended 2D materials including monolayer graphene and MoS2 by employing a push-to-shear strategy. We comprehensively examine the dynamic wrinkling-splitting-smoothing process and find that monolayer 2D materials experience stepwise instabilities along with different recovery processes. These stepwise instabilities are governed by the materials' geometry, pretension, and the elastic nonlinearity. We attribute the different instability and recovery paths to the local stress redistribution in monolayer 2D materials. The tunable instability behavior of suspended monolayer 2D materials not only allows measuring their bending stiffness but also opens up new opportunities for programming the nanoscale instability pattern and even physical properties of atomically thin films. Tuning the instabilities of 2D materials can control their wrinkling behavior for interesting physical properties, but still challenging. Here, the authors report a push-to- shear experimental approach to control the wrinkling patterns of monolayer 2D materials and measure their bending stiffness.

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