Scientists at the University of Pennsylvania believe that it is now possible to create a nanoscale circuit board which is so sensitive you can power it on light.
While people can believe silly things, like the world will end in 2012 and Apple makes value for money gizmos, Nader Engheta and Andrea Alů, have discribed the concept of an optical nanoscale circuit in Physical Review Letters: All-Optical Metamaterial Circuit Board at the Nanoscale.
Engheta wrote that funny things happen once things get down to the nanoscale.
Nanoparticles act like the elements seen in current devices. All you need to do is create nanoparticles of a specific shape, and made from specific materials, that would allow them to act as capacitors, resistors, and other well-known elements.
Besides making circuit boards jolly small if they were properly constructed they could use so little energy that you could run them off light.
So far they have only managed to get their ideas running on a computer. The next stage is to come up with a proof of concept for circuit elements. They think they will have done this in the next six months.