Molecular assembler

A molecular assembler, as defined by K. Eric Drexler, is a "proposed device able to guide chemical reactions by positioning reactive molecules with atomic precision".

[3] Likewise, the term "molecular assembler" has been used in science fiction and popular culture to refer to a wide range of fantastic atom-manipulating nanomachines.

In 1992, Drexler introduced the related but better-understood term "molecular manufacturing", which he defined as the programmed "chemical synthesis of complex structures by mechanically positioning reactive molecules, not by manipulating individual atoms".

The ring carries a thiolate group, which removes amino acids in sequence from the axle, transferring them to a peptide assembly site.

[6] In another paper published in Science in March 2015, chemists at the University of Illinois report a platform that automates the synthesis of 14 classes of small molecules, with thousands of compatible building blocks.

[9] A nanofactory is a proposed system in which nanomachines (resembling molecular assemblers, or industrial robot arms) would combine reactive molecules via mechanosynthesis to build larger atomically precise parts.

A typical nanofactory would fit in a desktop box, in the vision of K. Eric Drexler published in Nanosystems: Molecular Machinery, Manufacturing and Computation (1992), a notable work of "exploratory engineering".

The potential for such devices was part of the mandate of a major UK study led by mechanical engineering professor Dame Ann Dowling.

To produce a practical quantity of a desired product, the nanoscale size of a typical science fiction universal molecular assembler requires an extremely large number of such devices.

"[13] However, most published safety guidelines include "recommendations against developing ... replicator designs which permit surviving mutation or undergoing evolution".

One of the most outspoken critics of some concepts of "molecular assemblers" was Professor Richard Smalley (1943–2005) who won the Nobel prize for his contributions to the field of nanotechnology.

Smalley also believed that Drexler's speculations about apocalyptic dangers of self-replicating machines that have been equated with "molecular assemblers" would threaten the public support for development of nanotechnology.

In 2006, the U.S. National Academy of Sciences released the report of a study of molecular manufacturing (not molecular assemblers per se) as part of a longer report, A Matter of Size: Triennial Review of the National Nanotechnology Initiative[19] The study committee reviewed the technical content of Nanosystems, and in its conclusion states that no current theoretical analysis can be considered definitive regarding several questions of potential system performance, and that optimal paths for implementing high-performance systems cannot be predicted with confidence.

Research funding that is based on the ability of investigators to produce experimental demonstrations that link to abstract models and guide long-term vision is most appropriate to achieve this goal."

One potential scenario that has been envisioned is out-of-control self-replicating molecular assemblers in the form of gray goo which consumes carbon to continue its replication.

If unchecked, such mechanical replication could potentially consume whole ecoregions or the whole Earth (ecophagy), or it could simply outcompete natural lifeforms for necessary resources such as carbon, ATP, or UV light (which some nanomotor examples run on).