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).[1] 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.

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Any machine with atomically precise parts of nanometer dimensions; can be used to describe molecular devices found in nature

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Chemically or biologically produced molecule, or collection of molecules that can perform useful work

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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.

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A mechanical device that performs a useful function using components of nanometer scale and defined molecular structure; includes both artificial nanomachines and naturally occurring devices found in biological systems.

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Molecular machine [Kilian, Gryphon]

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Any machine with atomically precise parts of nanometer dimensions; can be used to describe molecular devices found in nature.

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