The Carbon Based Future of Computing?

The BBC (25 September 2013) reports that the “The first computer built entirely with carbon nanotubes has been unveiled, opening the door to a new generation of digital devices.”  Meanwhile, the Independent reports that “The next step towards the computers of the future has been taken, after engineers from Stanford University built the first working computer that uses carbon nanotube transistors (CNTs).”  This stems from a letter, published in Nature, in which researchers from Stanford University’s Department of Electrical Engineering demonstrated the operation of the first digital computer that replaces semiconducting silicon with carbon nanotubes.  The reporting of this story may has passed many people by, regardless of the fact that it could potentially have a huge impact on the world.

Why is this so important?

Many readers may be familiar with the term “Moore’s Law”, the observation made by Intel engineer Gordon Moore in 1965 that the number of transistors in an integrated circuit doubles approximately every two years.  A smaller number may be aware of how important this has been for the development of our modern, connected world, and to how much effort has been involved in trying to keep this predicted trend from slowing down.  For many years now, commentators have been predicting the end of Moore’s law and the problems that would result from this.  This has generally involved doom-laden pronouncements about fundamental physical limits, but the engineers at Intel, AMD and other semiconductor companies have generally kept up the pace.

One of the main problems with this process of continually shrinking the size of transistors is that they have become increasingly inefficient, which is why your laptop can get uncomfortably hot when it’s working hard. Carbon nanotubes – long, tubular structures of carbon atoms – have been touted as a possible solution to this problem, for the reason that their size makes it relatively easy to turn them into a switch where the flow of electricity can be controlled efficiently.  One of the best quotes in the coverage of the nanotube computer comes from co-author Prof. H.-S. Philip Wong “Think of it as stepping on a garden hose. The thinner the pipe, the easier it is to shut off the flow.”

How was this reported?

Both the BBC and Independent articles do a reasonable job of explaining the problems that have hampered the use of carbon nanotubes in building electronic circuits.  However, they are perhaps a little too quick to uncritically accept all of the researchers’ statements; there is no dissenting voice there at all.  This is quite different to many of the articles on reported medical breakthroughs that have been discussed on this blog.  There are also phrases used that may raise the hackles of electrical engineers, where someone has tried to simplify matters but has ended up making no sense.  A particular issue was the description of the method used to get rid of “metallic” nanotubes which can cause short circuits because they always conduct.  The BBC report states:

…the team switched off all the “good” CNTs, then pumped the remaining “bad” ones full of electricity – until they vaporized.

This gives the wrong impression of what’s going on, these aren’t “balloons” that can be pumped full of something until they go pop.  A much better analogy, and surely one that most readers could grasp, is that of an electrical fuse, which melts when too much electricity flows through it.  Anyway, it turns out that this particular phrase most probably comes directly from the press release from Stanford as it can also be found in the report on the University’s news site.  Of course, many would say that this doesn’t really matter to the average reader, but it should be possible to be understood without getting the basics wrong.

Another issue for your current author is the acceptance of statements like this from one of the authors of the paper: “and as for manufacturing, our design is compatible with current industry processes. We used the same tools as Intel, Samsung or whoever.”  Originally this seemed promising but reading the full paper I noted that the nanotubes were transferred from the surface they were grown on to a silicon chip using adhesive tape.  While this might be similar to the technique used in the discovery of that other carbon based wonder material, graphene, I’m pretty sure it isn’t part of the process that allows Intel engineers to make integrated circuits.  Not even those who used to dance around in multi-coloured bunny suits in the ’90s adverts!

M. M. Shulaker, G. Hills, N. Patil, H. Wei, H.-Y. Chen, H. S. P. Wong, and S. Mitra, (2013). Carbon nanotube computer, Nature, 501(7468), 526–530. doi:10.1038/nature12502