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Molecular mills can perform repetitive assembly steps using simple, efficient mechanisms

In conventional manufacturing processes, the production of large numbers of identical parts is typically performed by specialized, high-throughput machinery. Molecular manufacturing can follow the same pattern.

This schematic illustration shows a molecular mill performing a series of hydrogen deposition operations. A belt carrying molecular workpieces travels from left to right across the bottom. A second belt carrying molecular tools enters at the top left, circles around a bearing-mounted wheel, and exits at the top right. (Atomic detail in the mechanical parts is suppressed for simplicity and clarity.) Each tool enters carrying a hydrogen atom (white) bound to germanium (purple); each workpiece enters with an upward-facing carbon radical (green).

At the contact point, aided by pressure and thermal vibration, the hydrogen transfers from the germanium to the carbon, forming a stronger bond. In chemical terms, the carbon radical abstracts the weakly bound hydrogen from the tool; in operational terms, the tool deposits the hydrogen on the workpiece. Hydrogen abstraction is a simple, well-understood reaction.

Molecular mills based on more elaborate mechanical systems can hold tools and workpieces together for longer times and move them in more complex patterns. Systems of molecular mills can regenerate tools using molecular fragments derived from simple feedstock molecules (e.g., recharging a tool with hydrogen). On a larger scale, molecular mills can bring together and join nanoscale molecular building blocks (as large or larger than the workpiece shown here) to form still larger building blocks — mills can serve as the smallest-scale assembly mechanisms in a convergent assembly system.

Molecular mills can be extremely productive. A mechanochemical system using belts moving at 1 m/s with tools spaced 10 nm apart will perform 108 operations per second. A 104 atom mechanism (about 100 nm3 of solid structure) that transfers ~ 1 atom per operation will process its own mass in ~ 10–4 s. A system based on such mechanisms that performs 10 operations per net transfer of one atom (to allow for regeneration of tools) will process its own mass in ~ 10–3 s.

Molecular mills in molecular manufacturing:

Drexler, K. E. (1992) Nanosystems: Molecular Machinery, Manufacturing, and Computation. Wiley/Interscience, pp.386–392.