A Nanotech Primer
(Note: This is intended to provide more specific information regarding nanotechnology. It is not intended to replace the Nanotechnology Guide, but serve as a supplement, particularly for players looking to play characters with a scientific bent. - Hagalaz)
Approaches to Assembly
Two main approaches are used in nanotechnology. In the 'bottom-up' approach, materials and devices are built from molecular components which assemble themselves chemically by principals of molecular recognition, or material is deposited using an atomic force microscope to gradually build up a larger construct. In the 'top-down' approach, nano-objects are constructed from larger entities by removal of material using a atomic force microscope. It is possible to use both techniques in the process of building nanotech constructs, particularly for dry nanotech.
Wet nanotech, or bionanotech, constructs are assembled using DNA, self-assembling protein molecules, and/or gengineered viruses. It is referred to as 'wet' because water is required as the working medium where the building process occurs inside an assembler. These assemblers can produce robots on a nanotech scale, bottom-up, that structurally resemble bacteria. These bionanomachines can be introduced into a patient's bloodstream to provide medical treatments and cause 'soft' changes, altering skin or blood cell production, production of specific proteins, or editing genetic material in reproductive organs. Bionanomachines are designed to 'die' after a set period of time, at which point they are usually removed from the host organism in a manner similar to other dead cellular material.
Bionanotech cannot be used to cause 'hard' changes, such as reshaping existing organs, muscle or bone. Medical bionanomachines can only survive in controlled conditions, and must be tailored for a particular subject, or risk being attacked by the host's immune system and being destroyed.
It was rumored that at one time, bionanomachines were manufactured that would have been capable of application against a general population, capable of causing massive cellular death, blindness, sterility, or causing the host to succumb 'hereditary' diseases. This technology is not currently possible.
Dry nanotech is usually carbon-based (but other elements can and have been used) and would be produced in an assembler, using either a 'top-down' or 'bottom-up' approach. While the resulting nanotech constructs produced by an assembler would be quite robust, for example, starship engines made of a single large sapphire, or the anchor tether for an orbital elevator, the actual production must occur inside a sterile laboratory environment, in a specialized vacuum chamber, to minimize risks of contamination (which would prevent nanometer-scale ('nanoscale') machines from functioning due to misshapen parts, and would affect the structural integrity of large constructs). At this time, there is no way to produce new dry nanoscale robots capable of functioning outside of a controlled lab environment.
Micrometer-scale nanomachines, such as utility foglets, generally have a hollow, vacuum-filled body (often referred to as a 'vacuole') containing any nanoscale moving parts and protecting them from the outside environment, along with a power supply and any on-board processor capability. They are generally constructed from materials such as aluminum oxide, instead of carbon, to prevent creating a fuel-air explosive from what are essentially finely-divided microscopic carbon particles.