Two-Dimensional Mechanics of Atomically Thin Solids on Water.

Yu, Jaehyung; Liang, Ce; Lee, Myungjae; Das, Soumik; Ye, Andrew; Mujid, Fauzia; Poddar, Preeti K; Cheng, Baorui et al. · Nano Lett · 2022

basic_science · Level V

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Abstract

Movement of a three-dimensional solid at an air-water interface is strongly influenced by the extrinsic interactions between the solid and the water. The finite thickness and volume of a moving solid causes capillary interactions and water-induced drag. In this Letter, we report the fabrication and dynamical imaging of freely floating MoS<sub>2</sub> solids on water, which minimizes such extrinsic effects. For this, we delaminate a synthesized wafer-scale monolayer MoS<sub>2</sub> onto a water surface, which shows negligible height difference across water and MoS<sub>2.</sub> Subsequently patterning by a laser generates arbitrarily shaped MoS<sub>2</sub> with negligible in-plane strain. We introduce photoswitchable surfactants to exert a lateral force to floating MoS<sub>2</sub> with a spatiotemporal control. Using this platform, we demonstrate a variety of two-dimensional mechanical systems that show reversible shape changes. Our experiment provides a versatile approach for designing and controlling a large array of atomically thin solids on water for intrinsically two-dimensional dynamics and mechanics.