In 1997, Philip Collins, then a graduate student at Berkeley, won the Foresight Institute’s Distinguished Student Award for his experimental verification that a defect location in a carbon nanotube could form a near-perfect rectifier, as well as various other heterojunction device behaviors, as had been theoretically predicted just the year before. “Such junctions could provide electronic elements with sizes inaccessible by lithographic manufacturing.”
In the decade since, a wide variety of electronic devices and phenomena have been found in carbon nanotubes, including highly conductive wires and FETs. Yet no nanocomputer or other complex circuit has been built, and the the semiconductor industry roadmap does not call for sub-5-nanometer gate lengths before 2022.
We have the devices. What we do not have is simply the infrastructure that macroscopic technology takes for granted: the ability to sort and test parts; to cut and join materials; to create frameworks that can hold devices in designed relationships, and the ability to place parts into such frameworks. (Drexler sometimes refers to this as the “circuit-board problem.”)
And yet we should have. In 1959 Richard Feynman, in his seminal talk Plenty of Room at the Bottom, described a straight-forward, immediately actionable plan which would have resulted in exactly such an infrastructure well before 2000 if it had been followed.
Let us begin by quoting the relevant section of Feynman’s 1959 talk:
Now comes the interesting question: How do we make such a tiny mechanism? I leave that to you. However, let me suggest one weird possibility. You know, in the atomic energy plants they have materials and machines that they can’t handle directly because they have become radioactive. To unscrew nuts and put on bolts and so on, they have a set of master and slave hands, so that by operating a set of levers here, you control the “hands” there, and can turn them this way and that so you can handle things quite nicely.
… Now, I want to build much the same device—a master-slave system which operates electrically. But I want the slaves to be made especially carefully by modern large-scale machinists so that they are one-fourth the scale of the “hands” that you ordinarily maneuver. So you have a scheme by which you can do things at one- quarter scale anyway—the little servo motors with little hands play with little nuts and bolts; they drill little holes; they are four times smaller. Aha! So I manufacture a quarter-size lathe; I manufacture quarter-size tools; and I make, at the one-quarter scale, still another set of hands again relatively one-quarter size! This is one-sixteenth size, from my point of view. And after I finish doing this I wire directly from my large-scale system, through transformers perhaps, to the one-sixteenth-size servo motors. Thus I can now manipulate the one-sixteenth size hands.
Well, you get the principle from there on. It is rather a difficult program, but it is a possibility.
In a nutshell, the idea is to start from the macroscale machining and fabrication and move to the nanoscale without ever losing the general fabrication and manipulation ability.
Feynman famously offered prizes for the first steps in such a process, and the Foresight Institute continues to award prizes in his name for advances toward the capabilities he foresaw. However, there has not been a focused, coordinated effort to follow the pathway, or even a serious study of its feasibility.
The Missing Chapter of the Roadmap
As a member of the Foresight/Battelle Roadmap working group, I was the champion of Feynman’s scheme as one of the possible pathways. It was decided, however, that the Roadmap should focus only on those techniques which produced atomically-precise products. This seems a bit counter-intuitive, like insisting that the only territory on a map be that of the destination and exclude the starting point and intervening territory. However, there were sound political reasons for it, primarily as a hard stop to exclude the thin films and particulates “nanopants” nonsense from taking over the proceedings.
However, I feel that the time has come to examine the possibility of actually doing what Feynman proposed, and that is what I will do in the follow-on series of posts. You can, if you like, consider this the missing Roadmap chapter.