Molecular machine

A molecular machine has been defined as a discrete number of molecular components that have been designed to perform mechanical-like movements (output) in response to specific stimuli (input). It is often applied more generally to molecules that simply mimic functions at the macroscopic level. The term is also common in nanotechnology and a number of highly complex molecular machines have been proposed towards the goal of constructing a molecular assembler. Molecular machines can be divided into two broad categories: synthetic and biological.
Molecular systems that are able to shift a chemical or mechanical process away from equilibrium represent a potentially important branch of chemistry and nanotechnology. By definition these types of systems are examples of molecular machinery, as the gradient generated from this process is able to perform useful work.