  Strong coupling between electronic and mechanical degrees of freedom is a
basic requirement for the operation of any nanoelectromechanical device. In
this Review we consider such devices and in particular investigate the
properties of small tunnel-junction nanostructures that contain a movable
element in the form of a suspended nanowire. In these systems, electrical
current and charge can be concentrated to small spatial volumes resulting in
strong coupling between the mechanics and the charge transport. As a result, a
variety of mesoscopic phenomena appear, which can be used for the transduction
of electrical currents into mechanical operation. Here we will in particular
consider nanoelectromechanical dynamics far from equilibrium and the effect of
quantum coherence in both the electronic and mechanical degrees of freedom in
the context of both normal and superconducting nanostructures.
