Low-power light source runs on just 0.1 Watts

This state-of-the-art device has a diode-like structure like LEDs but, curiously enough, the way in which it produces light is actually closer to the cathode ray tubes used in the TVs and computer monitors of the past century. Under the influence of a strong electric field, each carbon nanotube acts as a tiny cathode ray tube that releases a high-speed beam of electrons from its tip. These electrons then hit a phospor screen kept under vacuum and, in the process, release a small amount of energy that causes the phospor to glow.
Building the device was a fairly simple, low-cost process. The researchers started by mixing highly crystalline single-walled carbon nanotubes with an organic solvent and a surfactant compound. They then painted the mixture on the cathode and scratched the surface with sandpaper, which allows the electrons to more easily separate from the tip of the nanotubes.