Two-Dimensional Mechanics of Atomically Thin Solids on Water

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 MoS2 solids on water, which minimizes such extrinsic effects. For this, we delaminate a synthesized wafer-scale monolayer MoS2 onto a water surface, which shows negligible height difference across water and MoS2. Subsequently patterning by a laser generates arbitrarily shaped MoS2 with negligible in-plane strain. We introduce photoswitchable surfactants to exert a lateral force to floating MoS2 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.

Automated summary

This study reports a method for the fabrication and dynamical imaging of freely floating MoS2 solids on water, minimizing extrinsic interactions between the solid and water. By introducing photoswitchable surfactants, spatial and temporal control of the floating MoS2 is achieved, demonstrating a variety of reversible shape changes in two-dimensional mechanical systems.