Jeremy Baumberg on Iridescence

17:53 Wednesday 6th July 2011
Drive BBC Radio Cambridgeshire

ANDY BURROWS: You know when you see that kind of rainbow effect on the back of a CD or in soap bubbles? Well scientists at the University of Cambridge have found that the same spectrum effect is used to attract bees to plants. And that could also help us to find new partners, would you believe. Earlier on I spoke to Jeremy Baumberg. He’s a Professor of NanoScience. It was fascinating. (TAPE)
JEREMY BAUMBERG: What’s interesting is people have known that butterflies are incredibly beautiful and attractive for many years. I don’t know if you’ve seen some of these blue butterflies from South America that everybody shows, these incredible blue shimmering things. But in fact some of our own butterflies are like that. So if you look at a Swallowtail it has green patches on it, and they look amazing. And the colour is produced in a really surprising way. So most of the clothes that you’re wearing, the reason they’re coloured, if you’re wearing any clothes, the reason that they’re coloured is because they have chemicals in them which absorb certain colors of light. And almost all the colour we have around us is like that. But you actually can produce colour in a different way, and that’s what some butterflies do. And now we’ve recently discovered plants do it as well. And why do they do it? Well it’s like why do you get interested in a particular shop window, or what catches your attention when you’re reading a paper, and there’s something compelling about images, or colours. And in fact that’s what plants are doing or butterflies are doing. They’re shameless advertisers. So these shimmering colours are actually produced from completely transparent material, like your fingernail, that sort of material. Those bits are chopped up in tiny structures. You might call them wonderful architectures. And they’re all about the same size as the wavelength of light. And so that’s about, it’s a bit less than a millionth of a metre across. So these are small things.
ANDY BURROWS: I always thought, with some colours, and no doubt you’ll correct me if I’m wrong here, some colours are effectively what our brain has translated them into.
JEREMY BAUMBERG: Ah yes. Well this is the interesting thing about why you draw .. why is the sun yellow? And the answer is the sun is not yellow, it’s just that you see a white patch on a blue background, and then your brain makes it yellow.
ANDY BURROWS: Exactly.
JEREMY BAUMBERG: So no, this is a bit different. Your brain is actually seeing something, but it actually knows it’s unusual as well. So in fact, and I’ll tell you a bit later, we’re actually making synthetic structures like this. And one of the applications is for security, like on banknotes or credit cards. And the reason is when you look at these things they really look fantastic. And your eye knows that there’s something peculiar about them. And one of the things your eye is picking up is the fact that they slightly change colour when you change the angle. So let me talk about the bee’s angle. Why is that an amazing thing? We’ve discovered that tulips, azaleas, they’re actually differently constructed than we expected. We didn’t see this shimmering. And the reason is because the shimmering’s not designed for us, it’s designed for bees. And bees don’t see the same thing as us. Bees actually see in the ultraviolet region of the spectrum. They can go into the blue green, but they don’t see red.
ANDY BURROWS: But they still find them beautiful though, and alluring and attractive?
JEREMY BAUMBERG: And in fact we have a whole load of bees in a big hive down in the Royal Society. And we’ve made these synthetic flowers for them. And there’s two different sorts of flowers. Some of them .. they all look the same colour, but some of them are irridescent. They have this sort of shimmering look in the ultraviolet part of the spectrum. And those are the ones the bees like. And so we’ve done numbers of experiments. We¬†have a nice sort of collaboration between people who are plant scientists, people who look after bees, physicists who understand colour, and nanoscientists who can try and make these synthetic things. And so what happens is the surface of the flowers is corrugated in different ways, and the bees see it as a shimmer, and in fact the bees really like it, and they want to come into the flower. But they actually come along a line for the particular colour. So they see, at one angle they see an ultraviolet colour they particularly like. And that’s the way they fly into the flower.
ANDY BURROWS: And so why is this important then?
JEREMY BAUMBERG: OK. Two reasons. One of them is actually understanding how plants attract bees is very important because that’s how we get all our crops. And at the moment we have problems getting bees to like crops. So that actually threatens our agriculture quite a lot. So a strong understanding of this is going to be very helpful. The other side is that we can actually learn a lot from nature. So we’ve started to realise how to make materials like this. And until very recently we could only make tiny amounts of them. It took very expensive technology, rather similar to what goes into our mobile phones, or our computers, to make them. But we’ve recently found ways. Because nature doesn’t do that. Nature finds ways for things to make themselves. It self-assembles them. So we’ve found ways to actually self-assemble these materials, a bit like opals. They’re lots and lots of stacked spheres. And we can make them in stretchful rubbers. Because the colour actually comes from the spacing of the structure, not from anything about the materials.
ANDY BURROWS: So on a very base level then Jeremy, could we attract partners by wearing certain colours? Could we make ourselves more attractive to prospective employers?
JEREMY BAUMBERG: Yes. We’ve made t-shirts of this stuff. I’ve got one just in front of me here. It’s a greenish colour, and if I stretch it it goes bright blue. So if I stretch it round a mobile phone for instance it looks fantastic, because all the edges are stretched, so it brings out the outlines. So if you wear it in your t-shirt it brings out your biceps, as you flex them. So that’s the idea. We can do exactly what the natural world does, and so you can use it for advertising. You can use it for anything really, where colour is important. And in the end what we’d like to be able to do is to make massive displays on the sides of buildings, or wallpapers which you can make out of these things, where you actually have a knob where you can change the colour of them for instance.
ANDY BURROWS: Right. I’ve just got a couple of questions, just very quickly. It is said, isn’t it, that advertisers have been known to use in the past say the same pitch on an advert as the scream of a child, or something that makes you look up anyway. But after a while that effect can wear off. So can this colour wear off as well?
JEREMY BAUMBERG: I have a colleague who says the last thing the world needs is more colour. I think there’s something very eye-catching about these sorts of materials. It doesn’t wear off for the bees. Generation after generation of bees are fascinated by these colours, and go to the plants. On the other hand, we’re filled with a worlds with lots of things that attract us. So I’m sure in the fullness of time there’ll be another sort of material which will come along. But they’re actually very compelling things. Whenever we give them to people they stretch them to pieces, literally. (LIVE)
ANDY BURROWS: He was just great. I thoroughly enjoyed speaking to Jeremy Baumberg.He’s a Professor of NanoScience at the University of Cambridge.

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