  Microelectromechanical systems, which can be moved or rotated with nanometre
precision, already find applications in such fields like radio-frequency
electronics, micro-attenuators, sensors and many others. Especially interesting
are those which allow fine control over the motion on atomic scale due to
self-alignment mechanisms and forces acting on the atomic level. Such machines
can produce well-controlled movements as a reaction to small changes of the
external parameters. Here we demonstrate that, for the system of graphene on
hexagonal boron nitride, the interplay between the van der Waals and elastic
energies results in graphene mechanically self-rotating towards the hexagonal
boron nitride crystallographic directions. Such rotation is macroscopic (for
graphene flakes of tens of micrometres the tangential movement can be on
hundreds of nanometres) and can be used for reproducible manufacturing of
aligned van der Waals heterostructures.
