Image of Atomic Structure
Atomic scale structure of the single 4-atom acetylene-rotor molecule (grey-white spheres) on the chiral (i.e. having handedness) PdGa surface (blue spheres are Palladium and red spheres are Gallium).

The smallest motor in the world — consisting of just 16 atoms – measures less than one nanometer or about 100,000 times smaller than the diameter of a human hair. The rotor rotates on the surface of the stator and can take up six different positions.

The special feature of the motor is that it moves exactly at the boundary between classical motion and quantum tunneling.