Chris Phoenix, the Director of Research for the Center for Responsible Nanotechnology has published a detailed design study for a personal-size nanofactory in the Journal of Evolution and Technology. The nano-factory would be able to rapidly manufacture a wide variety of advanced products with minimal resources. This would include the ability to produce more nano-factories.
A nanofactory uses molecular manufacturing principles, building products molecule by molecule from the ground up. Tiny fabricators manipulate atoms and molecules to make small parts and then join them together. In a nanofactory, thousands of these miniscule fabricators are used to perform multiple steps to assemble macro scale products, with the fabricators gradually increasing in size to become large robot arms. The various steps have been examined in isolation but this is the first published paper to look at a complete factory system in detail.
Phoenix says that every aspect of nanofactory design, other than the fabricator mechanisms, is already a reality within engineering and scientific practice and the development of fabricators is closer than anyone realises. Once developed he points out that the technology needs to be controlled in order to ensure it doesn't result in major environmental, military and economic disruption.