  Biological nanostructures change their shape and function in response to
external stimuli, and significant efforts have been made to design artificial
biomimicking devices operating on similar principles. In this work we
demonstrate a programmable nanofluidic switch, driven by elastocapillarity, and
based on nanochannels built from layered two-dimensional nanomaterials
possessing atomically smooth surfaces and exceptional mechanical properties. We
explore operational modes of the nanoswitch and develop a theoretical framework
to explain the phenomenon. By predicting the switching-reversibility phase
diagram - based on material, interfacial and wetting properties, as well as the
geometry of the nanofluidic circuit - we rationally design switchable
nano-capsules capable of enclosing zeptoliter volumes of liquid, as small as
the volumes enclosed in viruses. The nanoswitch will find useful application as
an active element in integrated nanofluidic circuitry and could be used to
explore nanoconfined chemistry and biochemistry, or be incorporated into
shape-programmable materials.
