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Nanotechnology Press Kit - Introduction to Molecular Manufacturing
Last Updated: Saturday, 29-Mar-2008 14:09:58 PDT
Introduction to Molecular Manufacturing (MM)
Manufacturing today works by cutting or deforming large chunks of matter, then fastening together the remaining pieces into products. Molecular manufacturing plans to be more efficient and make better products by assembling products directly from the smallest pieces: atoms and molecules. The basic idea is to develop a small set of chemical reactions that can be applied repeatedly to build large molecules, then control the sequence and/or position of the reactions by computer in order to build engineered molecular systems.
Molecular manufacturing is different from biology in that biological systems are not engineered. The functional properties of a cell, or even a protein, are complex and hard to predict. However, the process of building protein molecules from small molecular fragments is quite programmable, and scientists are developing the ability to design and synthesize proteins with desired properties. This will allow protein chemistry to be used in an engineering, rather than a biological, context. This would be one approach to molecular manufacturing. Other approaches using different kinds of chemistry may also work, producing better materials.
Eric Drexler has proposed two kinds of chemistry that might work. The first, in 1981, was protein chemistry as described above. The second, in 1992, was three-dimensional carbon lattice, similar to diamond. This would be synthesized by direct robotic operation in vacuum. Although the required chemical reactions have not yet been demonstrated, some of them have been simulated in detail. Despite this, some scientists assert that this kind of chemistry can't possibly work as planned.
Discussion of molecular manufacturing has been distorted by several factors. From the beginning, it has been associated with "gray goo" (runaway biosphere-eating self-replicators), leading to excessive fear and attempts to counteract that fear. It has also been associated with with extreme science-fictional projections-though it can be hard to tell fantasy from sober calculation, because the calculations predict some pretty amazing capabilities. In reaction to these factors, some mainstream scientists have attempted to shut down discussion entirely by declaring that molecular manufacturing is impossible or that its major proponents are not credible. Discussion has been further distorted by a variety of widespread conceptual confusions.
The position that molecular manufacturing is impossible is not supportable. Living organisms are not an example of molecular manufacturing, because they are not based on engineering but rather on interlocking complex systems. However, the biochemistry of life could be adapted almost unchanged to a molecular manufacturing system.
A few prominent scientists have nonetheless claimed that molecular manufacturing is impossible, and others have echoed them. However, study of their objections shows that the arguments are weak, based on intuition rather than calculation. Some of the arguments elevate engineering difficulties to the status of fundamental limitations. Others are built on basic misunderstandings of the proposals. See "Molecular Manufacturing Myths" for examples of arguments that have been advanced against the theory, and why they are incorrect.
Although there are some practical questions remaining to be answered, there is no scientific study demonstrating a limitation or problem with molecular manufacturing theory. Indeed, the chemical mechanisms of life demonstrate that machines of a sort can be constructed out of molecules and can build more machines. Thus the scientists who dismiss the entire field out of hand have not bothered to study it in any depth. An intermediate position is that some form of molecular manufacturing will be possible, but will be limited. This is usually based on the assumption