Shinya Aikawa and his colleagues from the University of Tokyo and the Tokyo University of Science have built transistors out of carbon nanotubes, which are thin but strong and flexible at the same time. The transistors can be folded to the point where the bend's radius is only a single millimeter — not quite a complete fold, but very close. It's the equivalent of folding it around the edge of a paper clip. As an added bonus the circuits were transparent.
The team built a field effect transistor (FET) entirely out of carbon nanotubes. Previously if you wanted a flexible and see-through FET you needed to use gold or indium tin oxide as electrodes. But gold isn't very transparent and indium tin oxide is brittle. Another innovation was using a thin substrate of polyvinyl alcohol, which is used in some glues as a thickening agent.
What they got was a transistor only 15 micrometers thick. The transistor did lose some performance after being crumpled about 100 times. That might be because some of the carbon nanotubes break down. But even so, it means there's potential for sticking electronics on surfaces where they don't usually do well – perhaps in something like a band-aid, which flexes a lot.
Image: American Institute of Physics