The use of nanotech would at first glance seem to allow the construction of almost anything at extremely short notice. However this has not been the case. It has been impossible to coordinate the actions of millions or billions of nanomachines to build macroscopic objects with complex internal structures. This has restricted the use of nanotech to producing objects with a high degree of translational symmetry, such as nanocomputers and component elements of larger structures, which are then used by bulk fabrication systems to build macroscopic products. This system, known as hierarchical manufacturing, is also considerably faster than building the complete product using nanoscale systems.
The products of nanofabrication are built in manufacturing cells ranging in size from cubic centimetres or smaller to many cubic metres. These cells can be flooded with various solutions and suspensions. The first stage is to position a single 'seed' assembler, containing a nanocomputer with the design of the desired product. The cell is then pumped full of a suspension of replicators than had been building copies of themselves in a nearby vat, which supplies many manufacturing cells. The replicators near the seed bond to it and are given information from the seed giving their exact positions relative to it and instructing them to bond with other nearby replicators. Continuing this process of attaching replicators where they are needed an assembler-crystal grows over approximately an hour into the shape of the product. The nanomachine scaffolding contains a vascular system through which solutions can be pumped by the beating of assembler-arm cilia and a system of datalinks for moving information across the structure. The process of growth is allowed to continue for considerably longer might seem necessary, to ensure that the assembler lattice is complete.
The replicator suspension is then pumped out of the cell and replaced by a solution containing raw materials and assembler fuels. This is pumped through channels in all parts of the scaffolding, providing assemblers with the chemicals needed to begin construction and carrying away waste heat. Just as a programmable replicator can build a copy of itself in about five minutes, it can build any other compact, stable structure containing 200 million atoms in a similar time. The billions of assembler arms now start to construct the product, starting from its core and working towards the surface. As sections are completed the replicator lattice is slowly disassembled by assembler arms on the edge of the section, its components washed away for reuse, and the fluid-filled channels are pumped dry and filled in. Finally the manufacturing cell is emptied of the solution containing unused materials and the product is sprayed clean with water and lifted out of the cell to dry. The entire manufacturing process from raw materials to finished product has taken about two hours and resulted in no waste that cannot be recycled.
An assembler vat can easily be used to produce many different types of product: all that is needed is the design and a manufacturing program. This has lead to the use of autofactories which, given the correct design sequence, raw materials containing the necessary atoms and a power supply, are capable of producing almost anything. Almost all buildings now contain factories which, together with engineering and design expert systems, allow the construction of almost any type of small product.
The place of manufactured goods in the economy has largely been replaced by simple raw materials, power supplies and, more importantly, both designs and design software. For example, any domestic factory can produce extremely sophisticated computer systems, making the software to design such computers the primary commodity. However, the design of complex nanosystems and active structures requires molecular-scale simulations that are beyond the capability of almost all domestic and most commercial computer systems.
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