One of the big ideas behind the Drexlerian flavour of nanotechnology has been positioning atoms and molecules to make tiny devices, gearwheels, rotors etc. One of he arguments against this , stated eloquently by Richard Jones in Soft Machines, is that Brownian motion (the constant jiggling around of atoms at any temperature above absolute zero) would hamper our efforts to build such structures, and perhaps we should look at Nature instead.
David Leigh and colleagues at Edinburgh University have done just that, with the first man-made “molecular motor” that can turn in either direction.