Nanocars are a new class of molecular machines that can roll across solid surfaces with structurally defined direction. They are molecules essentially composed of a few tens or hundreds of hydrogen and carbon atoms and are measuring one to three nanometers.
The nanocar is propelled step by step by electrical impulses and electron transfer from the tip of the STM. The resulting tunnel current flows through the nanocar between the tip of the microscope and the common metal track. There is no direct mechanical contact with the tip. The nanocar is therefore neither pushed nor deformed by the tip of the microscope during the race. Some of the electrons that pass through the nanocar release energy as small intramolecular vibrations that activate the nanocar's motor.