This article first appeared in Personal Computer World magazine, July 1996.
He was right. Today, it is possible to manipulate individual atoms as if they were marbles. In 1990 two researchers spelt out the name of their employer -- IBM -- using thirty five atoms of xenon, each one dragged into position on a crystal of nickel using the sharp tip of a Scanning Tunnelling Microscope. The conditions required were harsh -- an ultra-high vacuum at almost absolute zero -- but within the year other researchers were manually positioning individual atoms at room temperature.
But building entire molecular structures this way is impractical. The difference in scale between the constructor and the components is too great. What is needed is a tool that is itself atom-sized. Enter K Eric Drexler and his concept of the 'universal assembler'.
Drexler is perhaps the best-known exponent of nanotechnology, and some of his ideas are compelling. His proposed 'assembler' is essentially a sub-microscopic computer-controlled robot arm, able to manipulate and bring together atoms and reactive molecules such that chemical bonds occur at specific sites. To synthesise material on a macroscopic scale, billions of these assemblers will work in parallel. However, you only ever need to build one assembler, since each assembler has the ability to replicate itself.
One of Drexler's proposed assemblers is one ten-millionth of a metre in length, and made of 4 million atoms. Its structure is bewilderingly complex, a Heath-Robinson affair of grippers, rotary joints, worm drives, bearings, shafts and gears, each created from a few atomic components. The assembler itself will be constructed by bootstrapping, starting with an extremely simple tool made of only a few atoms, which will subsequently build a slightly more complex tool, and so on, all this marshalled by nano-computers. Drexler suggests building computers using logic elements made from sliding rods of atoms.
Although Drexler's assembler sounds far-fetched, funding agencies are already paying researchers to work on computer models of engineering structures such as bearings, hinges and pumps, all made from a few atoms. Workers at Xerox PARC, for example, have demonstrated the feasibility of molecular bearings which require no lubrication, constructed from several hundred carbon atoms.
Also under study is a "hydrogen abstraction tool", which can be precisely positioned over an atomic surface and can selectively remove hydrogen atoms from it. Such a tool could greatly increase the yield of diamond synthesis using the existing proven technique of Chemical Vapour Deposition.
The field of nanotechnology is seething with ideas and controversies. A recent article in Scientific American, for example, took a rather negative view, asking: What about thermal noise? Quantum uncertainty? Loose molecules? Out of control assemblers reducing the world to a grey goo? Within weeks, an extensive and convincing point-by-point rebuttal by a leading nanotechnologist was published on the web.
It is not hard to understand the scepticism with which many people view the ideas and promises of nanotechnology. Consider tiny molecular machines with on-board computers which enter our bodies and perform surgery from the inside; mouthwashes that contain tiny robots to look after our teeth; furniture that can change colour and shape; entirely new classes of substance, comprising billions of tiny molecular machines physically and computationally linked together to form a kind of super-crytalline structure. This might form a wearable fabric which responds to temperature; a flowable 'smart' paint that spreads itself evenly on your wall; ultra-thin layers of molecules that function as loudspeakers or huge video screens. Next to these, my voice-activated sellotape begins to look rather quaint.
When speculating about future technologies, an open mind is essential. But one's mind must not be so open that one's brains fall out. To date, Drexler and his nanotechnologists are theorists. They model their atomic machines using CAD packages, and look to the chemist and physicist to make the ideas actually work.
Perhaps it will never happen. But perhaps something like it will. Until then, nano news is good news.
Toby Howard teaches at the University of Manchester.