An international group of scientists has created the world’s smallest light bulb. They used a classic design with the most modern material—graphene. The miniature light has a carbon-based filament, just like Thomas Edison used in 1879 for the first commercially-viable incandescent bulb. However, the new version has one major difference—the filament is made from graphene, the wonder carbon that is strong, extremely conductive, and just one atom thick.
The scientists, from Columbia University, Seoul National University and the Korea Research Institute of Standards and Science, published their study in Nature Nanotechnology. To make graphene light up, they put electrical currents through strips of graphene attached to metal electrodes and suspended them over a substrate, which caused the graphene to heat up and produce light. The tiny bulb emits bright light that is visible to the naked eye, which is a fun visual confirmation, but that’s really not the point. The big idea is that graphene-based lights could eventually be integrated into chips to be used for flexible electronics or optical computing.
Researchers the world are trying to make optical computing systems that transfer data through light (photons), which should be much faster than traditional computing with electrons traveling across wires. Engineers have developed many approaches to do this, but have not yet been able to put a simple incandescent light bulb onto a chip because the filament must be heated to very high temperatures. Graphene solved this challenge because of its unique property in which heat transfer is inversely proportional to its temperature. Although the graphene strips were heated to above 2500 degrees Celcius in order to emit light, the high temperature was confined in hot spots in the center of the filament.
The team measured the spectrum of light emitted from the graphene and noticed interesting peaks at specific wavelengths, which they discovered was caused by interference between the light emitted directly from the graphene and light reflecting off the silicon substrate and passing back through the graphene. Kim notes, “This is only possible because graphene is transparent, unlike any conventional filament, and allows us to tune the emission spectrum by changing the distance to the substrate.” Looking ahead, the group is working to further characterize the performance of the miniature lights and developing techniques for integrating them into flexible substrates.