Clean Interfaces in Twisted Bilayer Graphene via Elastocapillary-Driven Directional Motion of Nanodroplets

Layered van der Waals (vdW) materials, characterized by an ultrahigh surface-to-volume ratio and weak interlayer interaction, readily encapsulate ambient contaminants, resulting in the formation of nanodroplets. These intercalated nanodroplets disrupt the interlayer coupling, thereby degrading the material's physical properties. Consequently, achieving an ultraclean vdW interface over a substantial area, particularly in suspended vdW materials, presents a significant challenge. In this study, we propose a novel strategy that utilizes the uniaxial stretching-induced curvature effect to direct the motion of nanodroplets within suspended twisted bilayer graphene (TBLG). This phenomenon is associated with elastocapillarity, a connection further evidenced by observable changes in the droplets' morphology. These deformed nanodroplets can move directionally in response to the thermally stimulated opening of the vdW interface, eventually leading to an ultraclean interface of TBLG sheets. Our approach not only facilitates mass transport at the atomic channels but also enables the achievement of clean vdW interfaces on a large scale.