Elastocapillarity-induced adhesion switching in nanochannels

The miniaturization of nanostructures and NEMS/MEMS is limited by the dramatic capillary pressures (>100 bar) that build up during drying or wetting. Understanding and controlling the resulting deformations and adhesion is critical for scaling down nanofabrication processes. In this work, we took full advantage of the atomic smoothness, mechanical strength and flexibility of 2D multi-layered van der Waals materials to design switchable nanocontainers/nanochannels by reversibly controlling the interfacial adhesion through capillarity. Our channels have sub-10-nanometre height and a flexible wall, whose mechanical configuration can be switched at will from open to closed by drying-induced capillary forces. Fast imaging of the channel closure reveals a stepwise motion, indicating adhesion front/meniscus depinning. We identified the geometry criterion for channel closure under the capillary pressure and analysed the elasticity-adhesion balance of dry channels to capture the condition for channel opening upon wetting. Our analysis yields the key geometrical and material parameters for the design of such elastocapillarity-switched channels. Finally, we used these channels as switchable nano-doors of nanocontainers entrapping sub-attolitre volumes.