In a recent blog entry, we wrote:
"What level of nanotech development are they referring to? It might be only today's nanoscale technologies; it might be up to the second or third generation of advanced nanotechnology; or it might include the implications of exponential general-purpose nanofactory production. Clearly, the differences are crucial."
This got us thinking about a potentially confusing aspect of our message. On the one hand, we see molecular manufacturing as a natural and inevitable outgrowth of today's nanoscale technologies. On the other hand, we see its impacts as being abrupt and disruptive. Why the apparent discrepancy?
Nanoscale technologies are rapidly gaining more control of the nanoscale, building more complex devices (such as this one that includes an actuator, a bearing, and several levers), doing more intricate chemistry under direct control (scanning probe chemistry just got a lot more flexible), and supplying more information to the manufacturing processes.
The recent announcement of "nanomanufacturing" as a goal by the National Nanotechnology Initiative highlights this trend. Nanomanufacturing is one step below molecular manufacturing. It aims to build precise nanoscale devices, but it does not specify that the devices should be built by nanoscale machines. This is a difference so small that it sounds legalistic, which illustrates that nanotechnology is moving toward molecular manufacturing. However, the difference is actually quite important in terms of implications, because it is nanoscale manufacturing systems that will make molecular manufacturing really take off.
Development of a nanoscale fabrication system capable of building copies of itself will enable two things: a vast increase in the amount of intricacy that can be built into nano-products, and a rapid scaleup of manufacturing capacity. These capabilities will, for the first time, allow complete large products to be built with the advantages of nanotechnology in every component. This is the source of the revolutionary implications.
To build a nanoscale device, information must be delivered to the nanoscale. Today's nanoscale technologies use a variety of clever methods to do this. Complex molecules can be built and mixed together to self-assemble. Reaction parameters such as temperature and reactant concentration can affect the product. Patterns can be built on substrates to guide the placement of nanoparticles.
Each of those methods, however, is limited in the amount of information it can deliver. The total amount for most processes and techniques is probably measured in kilobytes. This is enough to select from among thousands of potential outputs -- very useful in comparison with earlier manufacturing techniques. By contrast, specifying useful products (as opposed to components that will require subsequent traditional manufacturing steps) will require megabytes or gigabytes of data. To deliver that much data to the nanoscale requires nanoscale machines to handle it, converting the data into nanoscale manufacturing operations.
Nanoscale fabrication machinery is important for another reason. It raises the possibility of exponential manufacturing: using a manufacturing system to make double the capacity, then repeating that process a few dozen times until the manufacturing capacity has scaled up to kilogram-scale production of nano-structured components. Ten more doublings reaches ton-scale, twenty reaches kiloton-scale, and so on. Exponential manufacturing will make manufacturing capacity non-scarce: it will be possible to build as many factories as desired.
The other advantages of molecular manufacturing, such as scaling law advantages and the benefits of atomic precision, have been discussed on this blog and in our monthly science essays. There is little doubt that, when molecular manufacturing scales up to kiloton-scale, it will be utterly revolutionary. But why do we expect the impact to be so sudden?
Look again at the doubling numbers. To scale from one nanoscale fabrication system to a kilogram of them requires about sixty doublings. To scale from kilogram to kiloton capacity requires only twenty. This implies that, not long after we get the first fabrication system working, we will be able to build truly awesome computers, among other things. (The NEC Earth Simulator could fit inside a grain of rice, using two watts of power.) But even more importantly, in one-third of the attogram-to-kilogram time, we will be able to scale from one nanofactory to a million. In fact, it'll be faster than that, because the scaleup will require debugging time, while mere duplication can happen as fast as the machines can work.
Nanofactories have additional practical advantages, such as being able to build prototypes of a new product just as easily and inexpensively as they can build production runs. This should speed research and development substantially -- by orders of magnitude, in some cases. An encyclopedic list of these advantages would make this post too long.
In summary, the reasoning goes like this:
- Nanotech is working toward productive nanosystems.
- Nanofactories must be scaled up from nanoscale systems.
- Before this scaleup, nanotech products will be very limited.
- The scaleup can happen quickly.
- After the scaleup, lots of revolutionary products can be designed quite rapidly and built almost instantly.
Thus, although technical progress up to and including nanofactories may follow a relatively smooth slope, the impacts of that crucial last step will be revolutionary and disruptive.
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In August 2005, the Center for Responsible Nanotechnology 
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