Atomic scale engines: cars and wheels.

We introduce a new approach to build microscopic engines on the atomic scale that move translationally or rotationally and can perform useful functions such as the pulling of a cargo. Characteristic of these engines is the possibility to determine dynamically the directionality of the motion. The approach is based on the transformation of the fed energy to directed motion through a dynamical competition between the intrinsic lengths of the moving object and the supporting carrier.