Yesterday I was in the studio shooting some butterflies, and please do excuse the pun title. In this post I'll explain the shoot, species and reason behind scientists finding these species so interesting.
I took these photographs of the butterflies eyes because I need to shoot a moths eye soon for another technology. I see this as a practise run, but was happy with the results. The top photograph is comprised of 17 photos, the middle has over 30 and the bottom is made up of 11. The scales shot in the middle is of the Morpho, but is only a test shot. The real photograph will be taken soon under a microscope, as this just looks like a messy blur at the moment, and it's hard to distinguish any real detail.
Photonic crystals are precise arrangements of geometrical patterns at microscopic scales.
On butterfly wings, these patterns might be bumps, holes, ridges, hexagonal arrays or other shapes, often in 3-D arrangements. The shapes are spaced very close to the wavelengths of light in ways that intensify the reflected light of certain colors and absorb others. You’ve seen this effect in the colors in oil on water -- depending on the angle, some colors become vivid -- except in the case of butterflies, the effect is controlled by the genetic code for purposes such as species recognition, mating display, warnings to predators, and camouflage. The control is so effective that the colors can be seen from a wide range of angles, even when the butterfly is flapping its wings in flight. The iridescent blue of the Morpho butterfly (seen here to the left) uses this technique, while and the oranges and yellows of the Monarch are produced by pigments.
In other words, the shape and arrangement of these scales mess around with light so much that in theory, you could create different spectrums of colour by changing these shapes and arrangements. I photographed these two butterflies, the top being a Morpho (which I bought online) and the latter being an Ornithoptera Croesus (commonly known as Wallace's Golden Birdwing) which I found in one of the studios at university.
These can then be utilised within technology by creating brighter clothing, sensors that change colour with shape, more visible safety equipment and maybe one day even brighter teeth. A company called Mirasol have used this concept within flat screens to create a reflective membrane which increases battery life by 40%.
At the most basic level, a mirasol display is an optically resonant cavity. The device consists of a self-supporting deformable reflective membrane and a thin-film stack (each of which acts as one mirror of an optically resonant cavity), both residing on a transparent substrate.
When ambient light hits the structure, it is reflected both off the top of the thin-film stack and off the reflective membrane. Depending on the height of the optical cavity, light of certain wavelengths reflecting off the membrane will be slightly out of phase with the light reflecting off the thin-film structure. Based on the phase difference, some wavelengths will constructively interfere, while others will destructively interfere.
The human eye will perceive a color as certain wavelengths will be amplified with respect to others. The image on a mirasol display can switch between color and black by changing the membrane state. This is done by applying a voltage to the thin-film stack, which is electrically conducting and is protected by an insulating layer. When a voltage is applied, electrostatic forces cause the membrane to collapse.