Draw your own circuits with nanotube pencils.

Extreme Tech gets right to the point of a new technology – a mechanical pencil that can draw functional electronic circuits:

With MIT’s carbon nanotube pencil, the lead is formed by compressing single-walled carbon nanotubes (SWCNT), until you have a substance that looks and behaves very similarly to graphite. The difference, though, is that drawing with MIT’s pencil actually deposits whole carbon nanotubes on paper — and carbon nanotubes have some rather exciting properties.

In this case, MIT is utilizing the fact that SWCNTs are very electrically conductive — and that this conductivity can be massively altered by the introduction of just a few other atoms, namely ammonia.

There are two main takeaways here. The first is that MIT has found a form of carbon nanotubes that is stable, safe, and cheap to produce. Second, carbon nanotubes have been used in sensors before, but usually the process involves dissolving SWCNTs in solvents, which can be dangerous. Here, creating a carbon nanotube sensor is as simple as drawing on a piece of paper — either by a human, or an automated process.