Molecular nanotechnology (MNT) is the concept of engineering functional mechanical systems at the molecular scale.
[1] An equivalent definition would be "machines at the molecular scale designed and built atom-by-atom". This is distinct from
nanoscale materials. Based on
Richard Feynman's vision of miniature factories using nanomachines to build complex products (
including additional nanomachines), this advanced form of
nanotechnology (or molecular manufacturing
[2]) would make use of positionally-controlled
mechanosynthesis guided by
molecular machine systems. MNT would involve combining physical principles demonstrated by chemistry, other nanotechnologies, and the
molecular machinery of life with the systems engineering principles found in modern macroscale factories. Its most well-known exposition is in the books of
K. Eric Drexler, particularly
Engines of Creation. Detailed theoretical investigation, sections 4.3 and 4.4 below, have investigated the feasibility of molecular nanotechnology, but the topic remains controversial.