Chemistry World - Nanonails and Fish Scales

13 January 2008

Interview with

Mark Peplow, Chemistry World

Joining us now from the Royal Society of Chemistry: the Editor of Chemistry World, Mark Peplow.

Mark - Hello Chris.

Chris - This looks amazing. Non-stick at the flick of a switch?

Mark - Yes, it sounds fantastic doesn't it? This is a group of scientists from Bell laboratories in New Jersey in America.  They've created a material that switches from sticky to non-sticky just at the flick of a switch.  They've made this out of what they're calling nanonails.  These are, well, very tiny nails.  The head of the nail is about four hundred billionths of a metre across.  That's five hundred times thinner than a human hair.  A huge array of these nails which are made out of silicon, coated in a fluoropolymer that's kinda similar to what your non-stick pans are made out of.  Normally, liquids are repelled by these nail heads so they bead on top but if you apply a voltage it actually changes the electrostatics of the nails and it sucks the liquid around, underneath each of the nail heads and it spreads the liquid out across the surface.  Just as you would expect a liquid to normally spread out across any kind of sticky surface.  As soon as you take the voltage off again the nails regain their original properties and the water beads up again.  It actually works for lots and lots of different types of liquids.

Chris - Not just water?

Mark - Not just water, loads of liquids: oils, petrol, things like that.

Chris - What could you do with this?  It sounds pretty amazing.  What sorts of applications have been suggested for it straight away?

Mark - The scientists that have worked on it have suggested a couple of things.  One is using certain types of specialised self-cleaning surfaces.  At the moment what they're working on is to try and use it in very miniature labs, just the size of maybe a cm across (called labs on a chip).  There are ways of processing very small amounts of material and they're working on using these surfaces to move liquid from one place to another in this little chip.

Chris - Amazing, we'll have to watch that space.  It could come in handy in the kitchen as well.  Take us on a trip to Paris, because you've got some interesting insights locked away in amber as to what Paris used to be like in the past.

Mark - That's right.  What was Paris like 55 million years ago?

Chris - This is the city, not Paris Hilton!

Mark - Yeah.  Ask a palaeontologist and they'll tell you it was probably a tropical forest.  You look at the fossil record and the temperature record.  It suggests that it was covered in tropical forest, surrounded by shallow seas.  Chemists in Paris have found an interesting confirmation of this in amber.  Amber is just fossilised tree sap.  They found a piece from 55 million years ago in Paris and they've looked at some of the chemicals in it.  They found a very unusual chemical that belongs to a class of compounds called diterpenes.  They've looked at it and thought, 'what sort of tree chemical could this have come from?'  By doing a clever bit of chemistry they've worked out that it came from an acid called iso ozic acid.  This has only really been found in one type of tree before and it's an Amazon rainforest tree.  They're linking this as evidence to say that whatever type of tree this fossilised resin came from it was probably a tropical tree, an ancestor of the sorts of things that we see in the Amazon today.

Chris -   It was definitely growing there, this wasn't brought in from outside by various geological processes?

Mark -   No, they looked at various different amber deposits from the L'Oise river which is near Paris.  The tree that they're linking to is called the burandanga tree.

Chris - Sounds catchy.  Talking about rivers and things, fish live in rivers and people are doing interesting things with fish scales.

Fish scalesMark - This is great.  This is such a nice little story.  A little bit of detective work, really.  Have you ever wondered why fish scales are so shimmery?  For quite a while we've known that it has something to do with the fact that the fish scales have crystals of guanine in them.  Guanine is a chemical that's one of the information carrying molecules in DNA.  Interestingly, scientists in Israel have pushed this story one stage further.  Normally, when you grow guanine in the lab the crystals come out as a prism shape but they actually looked very closely using x-rays and electron microscopy at the guanine crystals that are found in fish scales.  They found that they were very thin plates, not at all like the prisms that you'd normally get.  More than that, the thin plates - the thickness and the separation of them is perfect for reflecting visible light because the thickness of it determines how good they are at reflecting certain wavelengths of light.  If you look at how much energy it takes to grow certain types of crystal it's a lot easier to grow normal prism crystals in the lab.

The fish are expending quite a lot of effort and energy to grow these very specialised forms of crystals.  The team that are working on these from the Weizmann institute - they think that the fish likely has an inhibitory factor in their skin that as the crystals are growing and growing is controlling the way that those molecules stack up together. That's what they're looking for next.

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