Everybody loves a lightning bug. Which is why as an adult I regret murdering so many of them in my youth and running around the backyard howling with their abdomens smeared across my arms and face and tongue like extraterrestrial war paint.
Alas, my backyard experiments in biomimetics were eventually shut down for unspecified, ethical reasons. Which is why I’m elated to see researchers in Belgium, France, and Canada pick up the torch of firefly inquiry. Specifically, they have managed to create a more efficient, brighter LED after studying the lantern of a firefly in the genus Photuris.
In short, fireflies use their bioluminescent bellies to woo mates. Sure, the yellow-green beacons are also handy in warding off predators and may aid in landing maneuvers, but the primary function is getting laid.* Each species utilizes a unique style; displays differ in pattern, height, and flash trajectory. The reason scientists find this interesting is because animals that have relied on reproduction via light emission for some hundred million years are likely to sport a few Darwin-o-rific adaptations we can steal.
Glow little glowworm, glimmer glimmer.
In dual papers published in the open-access journal Optics Express, researchers discovered first that a firefly in the genus Photuris has curious, irregularly-arranged scales on its underside that could “contribute to light scattering and, through this mechanism, [impact] the overall light extraction.” Likening the protruding scales to a factory roof, the team set to work quantifying the effect of such scales with fancy things like azimuthal angles, planar reference interfaces, and Snell’s law of refraction.
After determining that Photuris cuticles were indeed very cool, the researchers embarked on a follow-up study to see if the beetle’s anatomy might be applied to LEDs. Rather than re-engineer existing LEDs, the team was able to fabricate an overlayer that could be tailored to existing diode design. This was accomplished by bonding a layer of light-sensitive material to an LED, then using a friggin’ laser to etch out the factory-roof pattern.
And wouldn’t you know, the crazy assholes managed to increase LED efficiency by an incredible 55%. In fact, the resulting light extraction is even more efficient than the lightning bug that inspired the studies. In other words: More light, less energy – take that, Nature!
The papers’ authors note that further study of other firefly species may reveal even better adaptations for light extraction, and thus, more opportunity for biomimicry. Translation: “C’mon, just give us a few more grants. You know we’re good for it!”
*In an evolutionary turn, females of the species Photuris versicolor can mimic the mating flash of females from another genus (Photinus). The ruse draws in Photinus males, which P. versicolor then devours.
What’s more, since the female P. versicolor is so often occupied with eating chumps, the male P. versicolor will sometimes mimic flashes of her prey (instead of the species’ own mating flash) in an attempt to get her attention. If he succeeds in identifying himself before she kills him, they mate. But sometimes, she eats him afterward all the same.
Images via: Tsuneaki Hiramatsu
