"Molecular nanotechnology (MNT) manufacturing means the ability to build devices, machines, and eventually whole products with every atom in its specified place. MNT is coming soon—almost certainly within 20 years, and perhaps in less than a decade. When it arrives, it will come quickly. Molecular manufacturing can be built into a self-contained, tabletop factory that makes cheap products efficiently at molecular scale. The time from the first assembler to a flood of powerful and complex products may be less than a year. The potential benefits of such a technology are immense. Unfortunately, the risks are also immense.
Even a primitive diamond-building nanofactory can create products vastly more powerful than today's versions. Electrical power can be converted to motion, and vice-versa, with one-tenth the power loss and about 108 (100,000,000) times more compactly. Computers can be a billion times smaller and use a million times less power. Materials can be about 100 times stronger than steel. This means that most human-scale products would consist almost entirely of empty space, reducing material requirements and cost. Most of the rest of the product would be structural, easy to design. Even the simplest products could be software-controlled at no extra hardware cost. Manufacturing of prototypes would be quite rapid—a few minutes to a few hours. Because manufacturing and prototyping are the same process, a successful prototype design could immediately be distributed for widespread use. A designer working with a few basic predesigned blocks could design, build, and test a simple product in less than a day. Products with complex interfaces to humans or to their surroundings—information appliances, automobiles, aerospace hardware, medical devices—would be limited by the time required to develop their software and test their functionality. However, in some fields the high time and money cost of manufacture slows other parts of the development cycle; this effect would disappear. An explosion of new, useful products could rapidly follow the widespread availability of a nanofactory."
Source: Center for Responsible Nanotechnology