Butterfly Wing Colours May Reduce Bank Fraud

I love that headline.

From ScienceDaily, reporting on an article in Nature Nanotechnology last month, is a story about how some of nature’s colours have provided the inspiration for a potential source of encryption. You may have seen visual devices on bank notes – little holograms, for instance. These are difficult to reproduce without very specialised equipment, which makes it harder for counterfeiters to ply their fakery.

Harder, but not impossible. So those responsible for coming up with technical tricks to protect money are always looking for new, harder-to-copy methods for creating these sorts of identifying devices.

And nature has given them an idea for one: iridescence, which is when things – like butterfly wings, beetle shells, and the inside of seashells – appear to change colour when you view them from different angles.

Iridescence happens when something is made in layers that are translucent(that is, some light can pass through them), and usually with tiny structures in the layers. Light goes through the top layer, some of it bounces back out (at angles depending on the tiny structures) but some of it goes down to the next layer, where some of it bounces back out but some of it goes down to thenext layer, etc. But all of those reflections interfere with each other, and their frequencies are shifted with respect to each other, and they reflect differently off different bits of the tiny internal structures. Bottom line: the colours reflecting from objects made like this appear differently when viewed from different angles.

According to that article, a team have succeeded in artificially creating layers of material with those little microstructures. It’s a very complicated bit of nanotechnology to do so, and the end result could be a device that could more securely mark legit currency.

Thanks for the idea, nature.

A selection from the Natural History Museum

I loved the Natural History Museum in London. If animals, geology, or any of the natural sciences tickle your fancy then this place is a treasure trove. Like many boys I loved dinosaurs, and this place does them well. The blue whale and the hummingbird case – two very different points on the animal spectrum – were also favourites. The Museum has 860,000 items in its mammal collection, 58 million animals in total, five million pressed plants, nine million fossils, 300,000 rocks, and 2000 meteorites.

Ahead of a major new BBC TV series – Museum of Life – six members the Museum’s team of 300 scientists each pick a treasure in the Guardian that exemplify both what a special place it is and how marvellous nature is.