Articles

Firefly Lanterns Inspire LED Lenses

By Dr Jonathan D Sarfati

This is the pre-publication version which was subsequently revised to appear in Creation 35(2):53. under the name “Fireflies’ fantastic light transmission”

We have often reported on human designers copying the designs in nature.1 One promising field is how organisms generate and manipulate light. Bioluminescence, such as in fireflies and octopuses,2 generates light from chemicals very efficiently. Some butterfly wings reflect light in spectacular iridescent colours with scales acting as diffraction gratings, and have extremely black rims because of scales that trap light. This has inspired pigment designs.3 And moth eyes have an ingenious anti-reflective surface, with a nano-structure hard to duplicate.4

Fireflies are actually not flies but beetles.5 They use bioluminescence to produce light on the lower abdomen. In the larva, this glow seems to be a warning that their flesh is poisonous, and in the adult, the light helps to attract a mate. The light is produced by a chemical called luciferin,6 found in special cells called photocytes. In addition, it also requires an enzyme, luciferase, magnesium, oxygen, and energy via ATP (produced by the world’s tiniest motor7).

Not only is the biochemistry efficient, but also the light transmission. There are three layers: cuticle (window), photogenic (light-producing), and a dorsal layer. The photogenic layer produces light in all directions. This either passes through the cuticle directly or after reflecting off the dorsal layer. This is extremely reflective, because it is a finely-layered structure called a dielectric mirror.

And the window itself also has amazing fine structure. Normally, when light passes through a boundary between different materials, some is lost through reflection. This can be minimized through a process called optical impedance matching. It turns out that the cuticles on firefly lanterns have a very fine structure that does just this. It has very tiny ridges: 150 nanometres in width, 110 nm in height, and a period (distance between one high-point and the next) of 250 nm (1 inch = 25.4 million nm).8 This turns out to be the best dimensions to transmit the most light at the firefly’s peak wavelength of 560 nm (yellow-green). Incidentally, our eyes are most sensitive to the same colour.

Now, researchers at the Biophotonics Lab of the Korea Advanced Institute of Science and Technology, led by Ki-Hun Jeong, have duplicated this structure for an LED lens. This enabled 3% more light to be transmitted than a smooth lens. This sounds small, but in the quest to maximize energy efficiency, it’s a good start. The researchers say, “This biological inspiration can offer new opportunities for increasing the light extraction efficiency of high-power LED packages.”

Of course, a report made the usual fact-free homage to evolution, claiming “efficient versions of these nanostructures have been selected for over hundreds of millions of years.”9 But the practical research used design principles to duplicate these nanostructures. So if the plagiarized copies required brilliant design, how much more the originals?

References

1. See Scientists copying nature (biomimetics), creation.com/biomimetics.

2. Johnsen, S. and two others, A., Light-emitting suckers in an octopus, Nature 398(6723):113–114, 11 March 1999. See also Sarfati, J., Octopus suckers: glowing in the dark, Creation 21(3):6, 1999; creation.com/octopus.

3. Vukusic, P., et al., Sculpted-multilayer optical effects in two species of Papilio butterfly, Applied Optics 40(7):1116–1125, 2001. See also Sarfati, J., Beautiful black and blue butterflies, Journal of Creation 19(1):9–10, 2005; creation.com/blue; By Design, ch. 3, Creation Book Publishers, 2008. Some butterflies even produce a dual signal with two diffraction gratings super-imposed on single scales. See Ingram, A.L. et al., Dual gratings interspersed on a single butterfly scale, Journal of the Royal Society Interface 5(28):1387–1390, 6 November 2008 | DOI 10.1098/rsif.2008.0227; Sarfati, J., Butterfly brilliance: Dual diffraction gratings produce two colour signals, Journal of Creation 23(1):15–16, 2009.

4. Hadhazy, A., Moths’ eyes inspire reflection-free displays, LiveScience.com, 25 May 2010. See also Moth eyes inspire anti-reflective surface—but difficult to copy, Creation 32(4):11, 2010.

5. The European glowworm is the wingless adult female of the firefly family Lampyridae. Cave glowworms in Australia and New Zealand are generally larvae of fungus gnats, whose glow attracts midges, trapping them on sticky filaments.

6. The Latin lucifer just means “light-bearer”; the word itself has no connections to Satan, even if he is sometimes called that because he impersonates an angel of light (2 Corinthians 11:14).

7. Thomas, B., ATP synthase: majestic molecular machine made by a mastermind, Creation 31(4):21–23, 2009; creation.com/atp-synthase.

8. Kim, Jae-Jun and six others, Biologically inspired LED lens from cuticular nanostructures of firefly lantern, PNAS 109(46):18674–18678, 13 November 2012 | doi:10.1073/pnas.1213331109.

9. Hodson, H., Firefly glow lights up better LEDs, newscientist.com, 29 October 2012.

https://creation.com/firefly-lanterns-led-lenses