Hal Hodson, technology reporter
LEDs of the future may owe their shine to one of nature's brightest sparks, the firefly, which uses its bioluminescence to attract a mate.
Many insects have evolved light-bending biological features. The figeater beetle's bright green iridescence is achieved by selectively reflecting light, and moths' eyes contain antire?ective structures which boost light collection to let them go about their nocturnal lives. Like firefly bioluminescence, these features rely on tiny biological structures that selectively shift light either according to its colour or its polarisation. For example, if the wavelength of the incoming light matches size of the structures, it is reflected at odd angles, altering the perceived colour. The effect is similar to that of a diffraction grating or of polarised sunglasses.
Fireflies use this property to snag a mate: the brighter a firefly shines, the better its chances of attracting romantic attention. The light-bending nanostructures - known as lanterns, located on the outer surface of their light emitting organs - help send light into the environment efficiently by reducing the optical impedance between the air and lantern. This lets the insects maximise their light output while minimising their energy output. In all animals that rely on bioluminescence, efficient versions of these nanostructures have been selected for over hundreds of millions of years.
But researchers at the Biophotonics Lab of the Korea Advanced Institute of Science and Technology found another use for them: a better LED lightbulb.
Led by Ki-Hun Jeong, the team measured the dimensions of the firefly nanostructures with an electron microscope, then built replica structures onto the surface of an LED lens. Their new LED lens transmitted 3 per cent?more light than a traditional smooth lens, a small gain, but potentially significant in squeezing even more efficiency out of LED bulbs that are already dramatically more efficient than traditional incandescent bulbs.
Journal reference: PNAS, DOI: 10.1073/pnas.1213331109.
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