A lightbulb moment for the old-fashioned filament

Do you yearn for the soft, instant light of the incandescent bulb? Edison's invention could be back - in an even more efficient form than energy-saving fluorescents

As a metaphor, the "lightbulb moment" doesn't work so well now that we have to wait five minutes for a low-energy bulb to get going. But a group of researchers at the Massachusetts Institute of Technology (MIT) have had a bit of a lightbulb moment. The fondly remembered, but extremely inefficient, old-fashioned tungsten bulb could soon be modified to reuse its wasted energy. This would make it even more efficient than the new types of energy-saving LED and compact fluorescent bulbs to which we've switched in recent years.

Almost all the energy used by old filament bulbs is converted to heat, with only around 5% given off as light. In their paper, poetically entitled "resurrection of the incandescent source", the MIT team describe how infrared radiation, which would otherwise be wasted, can be reflected and reabsorbed through a structure of up to 300 layers around the filament, using nanotechnology. "It is not so much the material you make the surrounding structure from, it is how you arrange the material to create the optical filtering property that will recycle infrared light and let the visible light through," said Ognjen Ilic, from MIT's research laboratory of electronics. This research could lead, one day, to the introduction of a high-tech lightbulb with an old-world glow.