The Science of Nanotechnology

26 February 2006
Presented by Chris Smith, Phil Rosenberg


Picking apart some miniature morsels of science this week are David Carey, who provides the big picture on the world of nanotechnology, Donald Fitzmaurice describes how DNA may be used as scaffolding for the next generation of computer chips, we breach the boundaries between physics and biology as Stephen Webb discusses how new microscopes can see developing cancers at the nano-scale, and Neal Morgan explains how nanoparticles are stamping out stinky socks. Also on the show, Jim Clark digs up the ancestors of T. rex, and in Kitchen Science Derek and Dave dish the dirt on how gravy thickens.

In this episode

- Digging Up The Ancestors

The Naked Scientists spoke to Professor Jim Clark, George Washington University

Digging Up The Ancestors
with Professor Jim Clark, George Washington University

Chris - Now you've been out in China looking at some interesting things to do with dinosaurs. Tell us about your work.

Jim - For the last five years I've been working with Dr Xu Xing of the Institute of Vertebrate Palaeontology in Beijing, and we've been going out to Xinjiang in the Gobi Desert of far western China. Our most recent discovery is a kind of ancestor of T. rex, a thing we call Guanlong.

Chris - It's a nice name, but what does it actually mean?

Jim - It means crested dragon.

Chris - And was it a crested dragon?

Jim - Yes, well it has a big crest running down the top of its head which we were surprised to find once we'd dug the skeleton out.

Chris - Why is this so important?

Jim - For one thing, it's very very old. T. rex was about 65 million years old and we're at about 160 million years old. So we're older in the other direction from T. rex than T. rex was from us.

Chris - That's a significant difference isn't it because 60 million years ago is roughly when the dinosaurs were thinking about being hit by a meteorite and disappearing for good. 160 million years must be way back in the really early origins of T. rex.

Jim - It is. It's really when the dinosaurs first started growing, and when the first big dinosaurs appeared.

Chris - So what big unknowns does this fill in in the field?

Jim - Mainly it helps us verify that T. rex and the Tyrannosaurs were relatives of the kinds of dinosaurs that were giving rise to birds and the timing of all that is really back there at the beginning of the surge of dinosaur evolution in the Jurassic.

Chris - So given that this early dinosaur is a stepping stone from other dinosaurs into what became the T. rex lineage, can you just set the scene? What would he have looked like?

Jim - Well it would be a fairly gracile animal. Unlike T. rex it had long forelimbs, which is one of the things that's placing it with theropods which gave rise to birds. Guanlong wasn't terribly big but it wasn't terribly small, so it was about twelve feet long from the toe down to the end of its tail. And we're guessing that it's a fast agile animal but of course that's something that you don't have a good handle on with fossils.

Chris - One view is that Tyrannosaurus rex wasn't agile and quite lumbering. Is that a reasonable thing for people to assume?

Jim - There is some very good work that was done based on how big the muscles would have to be on an animal as big as T. rex to move it quickly. Basically they couldn't find any way to put enough muscles on T. rex to move it very quickly. That's not the case with our finding because it's smaller. So ours could have been faster but again, this is all fairly speculative.

Chris - It's very early and not before seen. It's come from a region of China that's not been looked at very closely for dinosaurs, hasn't it?

Jim - Well there was some really interesting earlier work done by a joint Canadian - Chinese group in the late 1980s. They found some intriguing things but that was right at the end of their expedition. Phil Curry, on eof the leaders, has told me that it's one of the places he'd really like to go back to and explore in China.

Chris - And where will you be taking this research next?

Jim - We're continuing to study the fossils we've found. There's a huge area still out there too. It's the same area in which Crouching Tiger, Hidden Dragon was filmed. The badlands go on for a hundred kilometres or more, so there's a huge area to look in.

Chris - And presumably you want to fill in the gap between 160 million years and the 60 million years to the modern Tyrannosaurs.

Jim - Well you'd like to. Of course we're committed to these beds right now at 160 million years. I've worked in some younger beds before but I really like these older beds. We're really getting down to the base of some interesting lineages.

- The Bigger Picture of Nanotechnology

The Naked Scientists spoke to Dr David Carey, University of Surrey

The Bigger Picture of Nanotechnology
with Dr David Carey, University of Surrey

Chris - Nanotechnology. It's a term that gets bandied about in the media a huge amount but people probably don't understand terribly much about what it means. Would you mind making it a little bit easier for us to understand?

David - There are a couple of ways in which you can look at nanotechnology. The first one is what we refer to as the top-down approach. In other words, we take things that are large and try and make them smaller. That would be the sort of work semiconductor fabrication companies are involved in when they try to make transistors smaller and faster. The other way is to use self-assembly and to allow the atoms or molecules or things on a nanoscale to do the work for you. What you do is arrange particular materials and treat them in a particular way. By doing so they self-assemble and form interesting materials.

Chris - When we're talking nanotech, how big is nanotech?

David - Well if you sort of imagine the size of the planet Earth and imagine a football, the ratio between them is about ten to the power of eight. If you then scale down a football by that same ratio, tha'll take you to roughly the size of a carbon60 molecule, or a buckyball. If you go smaller than that, then you'reinto the area of DNA and single walled carbon nanotubes. So it's really at the ultimate scale of length.

Chris - And the reason that it's become a technology that we've embraced only recently is presumable because it is so small and there are constraints when working at this scale.

David - There are lots of constraints but there are also lots of advantages of working at this scale. The constraints are how you can see, manipulate and move these things. But one of the key aspects is how you can take the benefits of this nanoscale. When you get this small, two things really happen. The first is that the surface area to volume ratio changes, so bascially your nanomaterial is all surface. Volume plays much less of a role and the surface is the key. The other thing is that when you're at these very small scales, you're dealing with quantum effects. This rather weird area of physics takes over and you get unusual properties that you don't get with the bulk of the material.

Chris - So they're not a nuisance, they're actually quite useful.

David - They can be very very useful. In fact, there are a number of applications for them in the biotechnology industry. The displaying industry are very interested in using these carbon-based electronic materials to extract electrons and use them in displays for example.

Chris - Are we going to get better television sets out of this?

David - Well that's the ultimate goal. Samsung for example have developed a new type of cathode ray tube.

Chris - You'd better tell us what that is.

David - If you imagine your television and it's got a single source of electrons and the electron gun. If you then want to give your television a wider screen, it also has to get deeper, heavier and more expensive. The other way round it is rather than having a single source, you have billions and billions of sources of electrons. That means that you can have these sources quite lose to where the phosphors are. The phosphors are the things that glow red, green or blue in your TV screen. Getting them very close means that you have a very thin display. A thin display is potentially a cheaper display, but it's also light in weight.

Chris - So just explain the difference between a plasma or LCD screen and a normal television.

David - An LCD or liquid crystal display essentially uses particular molecules that under certain conditions either allow light to go through or they block light. So they tend to be permanently on as a technology, and what you're doing to make something go dark is to put something in the way of it. So that's inherently rather energetically inefficient. In plasma screens, you're setting up and electrical discharge and that tends to use very high voltages and that tends to mean that your display becomes very expensive.

Chris - So how do you actually create that discharge? What's actually happening?

David - What's happening is that you have a gas within a chamber and you're setting up a high voltage discharge which then breaks down and gives off particular colours. By modulating that high voltage you can make it glow red, green or blue.

Chris - So it's a bit like a strip light that's illuminating this studio but obviously in a much more controlled way.

David - Yes that's one way to look at it. But these things tend to be very energetically inefficient and power hungry and you have to use very large areas of silicon as a substrate, which is also expensive.

Chris - So how is nanotech going to make us have much better screens then?

David - The idea is that you can use materials that give off electrons very easily, such as what are called carbon nanotubes. A carbon nanotube is a single sheet of carbon atoms which are arranged in hexagonal rings.

Chris - A bit like graphite then.

David - Exactly like graphite. Graphite is a layered material and the layers are called graphene. If you were to take on eof those graphene layers and roll it up, that would form a single-walled carbon nanotube. You can have single walled ones of these or you can have multiple walls, a bit like a Russian doll structure. These things, because they have a very high aspect ratio, when you put the into an electric field they give off electrons very easily. Those electrons then hit off the phosphorous and therefore your television is red, green or blue.

Chris - How do you make the different colours though? I can understand how you get the electrons out but do you therefore have to connect the nanotube to something that glows a certain colour or gives off a certain colour when it gets excited?

David - What happens is the electrons come off of the carbon nanotube, are accelerated towards towards a phosphor in a straight line and you just decide in your structure that one third of your screen will be red, one third will be blue and one third will be green. It's all to do with the control electronics when the electrons turn on and when the electrons turn off. That's how you get the different colours on a screen.

Chris - Can you just give us the idiot's guide to how these phosphors work? That's the coating on the screen that the excited electrons hit and is then encouraged to change colour.

David - That's right. There are different types of phosphors and phosphorus materials but one type is called the rare earth based phosphors. These are rather interesting materials. Most materials when you shine light on them will glow at different colours, including red, green, blue and a mixture. The rare earths are rather unusual because when light hits them they give off light in very well defined wavelengths. The narrowness of that wavelength is basically the narrowness of your colour. This gives you a very clear and clean image.

Chris - Can we focus on these nanotubes because they really are an exciting bit of science aren't they? Didn't Sir Harry Kroto discover these things and get the Nobel prize for making them or something?

David - Harry Kroto got the Nobel prize for the discovery of C60, which is a molecule of sixty carbon atoms. This was partly when he was at Sussex University but he then went to Rice and did some experiments with the late Richard Smalley. What happened there was that they found C60 molecules by hitting a laser into graphite. Carbon nanotubes came about and were discovered by a Professor Iijima in Japan to some extent by accident. He was trying to do a similar experiment and he looked at the material that was left over expecting to see some C60 molecules because that's what he was interested in. To his surprise, he found some long helical structures made out of just carbon atoms. He then wrote this up and submitted it to Nature and it's been one of the most highly cited papers since 1991 and it's developed the whole field of carbon nanotube electronics.

Chris - Ok, so that's electronics taken care of and I've got a little question for you about nanotubes in a second. But obviously nanotech is a much broader field than that. So set the scene for other things people are doing with it.

David - Nanotechnology and nanomaterials can be used in a number if different areas, particularly in catalysis, enhancing reactions, used in fuel cells, and there's a huge patent portfolio for using nanotechnology for cosmetics.

Chris - Really, how?

David - Well you're dealing with a product that you can rub onto your skin. If you think of things like sun screen, five years ago, they were all coloured pigment. Now if you look at a lot of sunscreens, they're actually clear. This is because the size of the material, the titanium dioxide material has got smaller, and will hopefully improve the response and protection towards the sun. But there are a whole rang eof these nanomaterials that are beginning to emerge in unusual areas such as skin care and things like that.

- How Nano Is Borrowing From Biology

The Naked Scientists spoke to Professor Donald Fitzmaurice, University College Dublin

How Nano Is Borrowing From Biology
with Professor Donald Fitzmaurice, University College Dublin

Chris - Now we're going to find out about a very interesting application of nanotech from Donald Fitzmaurice, and that's powering the next generation of microprocessors potentially with DNA.

Donald - Indeed. Well maybe I'll just back up a bit and say why we want to do this kind of work. Every one of us has got used to going into our local computer store and buying a PC that's twice as powerful and half the cost compared to the last one we bought just a few years before. That's a huge achievement by the electronics industry where they're able to deliver improved performance at reduced cost year on year. That's governed by something called Moore's Law, where the number of transistors on a wafer doubles every 18 months.

Chris - In other words, the processing power. The number of transistors doing the computing power on the chip.

Donald - Right. And the reason that works is because if you want to do a computation on a computer, you have to move electrons around. If you want to shorten the amount of time you want to do a computation, then you have to bring everything closer together. The way you bring everything closer together is that you make it smaller and shrink it. Now that's been going on now for four decades since Gordon Moore first observed this. It's a huge achievement and it's really underpinned a revolution in the way we do everything in our lives nowadays in certain parts of the world. But for us to be able to continue increasing processing power at this rate, we're going to have to keep shrinking the bits that make up a computer. That presents us with two problems: one is that making stuff that small is really hard and very expensive, and secondly when you move electrons very close together, they start to know about each other.

Chris - Quantum effects.

Donald - Yes, you get quantum effects and also you get power-density effects. So the effect of current inside these things goes way up and the power-density inside a Pentium 4 processor is approaching something like the power density inside a small star.

Chris - Good grief! So quite literally, what you have is one tiny component here getting so close to the second component here that the two begin to interfere with each other and there's therefore a theoretical limit to how many things you can pack onto one computer chip.

Donald - Exactly. If one electron is in the wrong place and they're all repelling each other, you need a lot of energy to force them through. The amount of energy you're putting into one small space is so much that it's something like the same amount of energy you'd find in a star.

Chris - So does this mean that in the near future we're looking at a theoretical maximum processing power given current technology?

Donald - Well there's the so-called industry road map and this predicts the rate at which processing power will increase, or in other words, how fast the components of a computer will shrink. What they believe is that they can continue to halve this size of transistor every 18 months for about the next possibly ten years maximum. The industry will then hit what's called the red wall. They just don't know what's going to happen after that. So all the big semiconductor companies and lots of other types of companies are interested in developing different ways and different approaches to making electronic devices that will get us around these problems.

Chris - So what's the answer.

Donald - Well there's two things. One, you have to think of new ways of making them fundamentally. If you look around us you find that biology is very good at making lots of things that are every small and packing them very close together so that they all work without interfering with one another. The way biology does that is to start with atoms, assembles them into molecules, assembles those molecules into collections of molecules and into larger collections of molecules. You've got a hierarchy of function all integrated. Of course, you see this in every day of your life. You're having a shave in the morning and you cut your face. You come back 24 hours later and that cut is gone. Well millions of operations have taken place to remove the damaged cells, to clear up any infection, to build new cells and put them into exactly the right place. Now let's say that cut is on your finger. Not only does it repair the skin, but it puts exactly the same pattern of the fingerprint back. So it's extremely remarkable and there's a lot to be inspired by from nature.

Chris - So you're advocating borrowing from biology but translating from a cut on a face to a computer chip sounds challenging.

Donald - We're working closely with our colleagues in University College Dublin and a number of colleagues at the Centre for Research in Adaptive Nanostructures and Nanodevices at Trinity College Dublin and particularly now with the folks at Intel and various other companies. What we're trying to do is combine the best of both approaches. We're using conventional methods from the semiconductor industry to build really smart substrates that will help us organise molecules. Then we're taking lessons from nature and what we're doing is building molecules which organise on that substrate and assemble nanoparticles of metal and semiconductor and insulator into the right place and build the device as we want.

Chris - So literally you can use other molecules that know how to have a shape and a structure to move other particles into just the right place to do something useful.

Donald - Exactly.

Chris - So if you focus in on DNA for example, we know it forms a rather nice helix and if you have a certain sequence of DNA it forms other structures as well. I presume that's where you're going to go with this.

Donald - There are some very nice things about DNA as a potential molecule as a basis for this approach. One is that it has information intrinsically stored in it in the form of a sequence of base pairs. That's how biology stores information about it's own future and past. Secondly you can produce DNA in any sequence virtually at the touch of a button in a current laboratory. The whole process is automated. So it's not only an attractive molecule from an intrinsic point of view but it has the potential to be scaled industrially if you ever wanted to do that.

Chris - But is that actually do-able Donald? The idea of getting DNA to organise molecules in the right place to make an electrical circuit sounds like a great idea but also sounds pretty difficult.

Donald - It is.

Chris - Have you actually tried this yet?

Donald - We have tried it and indeed a number of other groups around the world have tried it and there is growing success in this approach. So much so that companies such as Intel and various other companies are actively exploring this approach and pushing a lot of resources into it.

Chris - So you've almost got a living chip then.

Donald - Exactly. Let me explain to you one or two of the things that have been done. I suppose the simplest experiment that has been done is you take a conventional electronic substrate which has somewhere where the electrons can come from and go to, and conventionally you might connect that up with a piece of metal. Now you can connect that up with a piece of DNA which is just the right length and swims through the solution and sits down on the surface because it recognises the place on the surface that it should sit. You then build nanopaticles of, say, gold or copper and they know how to recognise a certain part of the DNA and they sit down and lie between the two electrodes. Now you can pass electrons from one end to the other.

Chris - And it's much quicker because it's much smaller. But how many years of technology will this buy us?

Donald - There's two things: one is that in principle it should be possible to build very small wires but also, and this is more important, it's in principle possible to build lots of wires in parallel very inexpensively. There are two problems here. It's not only what you end up with, but it's how hard it is to make it. So this approach offers the possibility of building new things with new function that overcome the power-density and the interference problems, but it also offers a way of making things in a massively paralleled approach. I'll just give you an idea about that. Let's say you put molecule A and molecule B in a beaker. So you've got a beaker with molecule A and a beaker with molecule B, and you pour the two into another beaker. These come together to form molecule C. If you have just 100ml of each, you can be making something like 10 to the power of 27 new molecules in a few minutes.

Chris - That's one with 27 zeros after it. Which is probably more than there are stars in the known universe actually.

Donald - Yes, so in principle, using this approach, you can make more transistors in a few minutes than have ever been made in the history of human kind before. Whereas ten years ago that was seen as very fanciful talk, and for good reason because the problems facing us were very significant, groups around the world have made enough progress to make this at least a possibility. I wouldn't for a second suggest we're there. There's a huge amount of work yet to be done and it's still a great challenge to turn this into a commercial scale technology, but it's no longer one that hasn't got a chance.

- Watching Cancers At The Nano-scale

The Naked Scientists spoke to Dr Stephen Webb, Daresbury Laboratory

Watching Cancers At The Nano-scale
with Dr Stephen Webb, Daresbury Laboratory

Chris - Tell us about your work, literally zooming in and seeing things on the microscopic level and cancer in action.

Stephen - That's right. In many cancers there's a molecule called epidermal growth factor receptor involved. You may well have heard about herceptin in the news recently. It's involved in one of a family of four molecules of which epidermal growth factor receptor is one. What happens in order for the cell to divide is that a signal has to come in in the form of a molecule from another cell. This molecule attaches itself to the epidermal growth factor receptor on the cell membrane. When that happens, there is a change in the shape of the receptor molecule. It would be possible if we knew exactly what the change in shape was and how it progressed in time for somebody else to take this knowledge away and design a drug which prevented it.

Chris - In other words, just block up the receptor so that the cancer cell doesn't hear that signal.

Stephen - Yes, and this is a normal process. It happens in all our cells anyway, it's just that it basically goes into overdrive in cancers. So what we can do to exactly see what this change of shape is, is to attach little fluorescent tags to different parts of the receptor molecule. There are things like green fluorescent protein (GFP) that's been extracted from jellyfish and you can stick that into the molecule. You can attach quantum dots, which are little cadmium selenide molecules. These are very small little nanoparticles, which you can tag onto the different parts of the receptor molecule. If we excite them with a laser, they will then emit fluorescence and the wavelength of the fluorescence that's emitted and the polarisation of the fluorescence gives us information both on the distances and angles between different fluorescent tags on different parts of the molecule.

Chris - So you can begin to build up a three-dimensional picture of what this docking station receptor looks like on the cell surface.

Stephen - That's right. The idea is that in real time we can see exactly the change sin shape that are occurring in this molecule.

Chris - And what about if you throw a drug on. Does it tell you about what happens to the receptor when they're present?

Stephen - That's the idea in the future. Herceptin only works on HER2 of this family of four molecules. All four molecules are involved in different cancers and we want to study all of them.

Chris - So you've been able to label individual parts of the receptor in order to see how they all interact. How is this going to translate into a new form of herceptin and in what sort of time scale? How is this better than the traditional way of doing things?

Stephen - The receptor molecule itself and its structure has been studied using things like x-ray crystallography. This gives you a static picture of what the molecule looks like and it tells you what it looks like in solution rather than in an actual cell, which is a completely different thing altogether. What we can do is look at the receptors in real cells and in real time. Hopefully this will be a quicker and more physiological method of getting the basic science necessary in order to design a drug. You could study how the drug was working and how effective it is by using these microscope methods as well.

- Stamping Out Stinky Socks With Nanoparticles

The Naked Scientists spoke to Neal Morgan, Cambridge University

Stamping Out Stinky Socks With Nanoparticles
with Neal Morgan, Cambridge University

Chris - Now you've all been waiting for this! The nanotechnology behind smelly feet! But there's a serious side behind this too isn't there Neal?

Neal - There is. This is basically to do with nanoparticles and more importantly, functional nanoparticles. A group in ETH Zurich University in Switzerland came up with idea of mass producing lots of silver oxide nanoparticles. These are basically very tiny particles of silver oxide.

Chris - How tiny?

Neal - We're talking anything from a few molecules up to a few thousand nanometres. So basically we're talking a billionth of the size of the coffee cup in front of you there. The purpose of these particles being so small is that their surface area to volume is incredibly high, which makes them incredibly reactive. Silver itself is very good at killing bacteria, so the idea of this spin - off company was to mass produce silver nanoparticles which would then be put into socks. When you put your socks on, the bacteria which would cause the nasty smells would be killed off and hopefully you won't have smelly feet.

Chris - A few foot facts for you: the average person sheds about 40 000 skin cells every single minute, which over a lifetime will weigh about three or four stone in dead skin. The sweat glands in your feet squirt about a litre and a half of sweat into each of your shoes on a roughly daily basis. So if you put the two together, you get a pretty stinky combo. It's interesting about silver. Do you know why it has this profound antibacterial effect?

Neal - I'm afraid I don't specifically know why, but I know that lots of companies are investigating this and I believe one of the big plaster manufacturers has started to put silver into their plasters for specifically that purpose. This makes specific antibacterial plasters for cuts and grazes.

Chris - It['s easy to think of this as a new technology, but it's not though is it? There's evidence that the ancient Egyptians knew about this because they used to put silver into some of their drinking water because they knew it killed bugs. Of course, water-borne illnesses cause a hell of a lot of problems where you've got sun, people and pollution all coming together to give people food poisoning. So tell us about these socks a bit more. How do you actually attach the particles onto the fabric so that when you put the socks through the wash, they don't all fall off?

Neal - The particles themselves are then incorporated into the dyes so you'd mix them up with the dye products and they become suspensions of these particles. When you spray that onto the fibres they become intertwined with the cotton and that's why they don't just fall out and give you piles of silver nanoparticles in the bottom of your shoes.

Chris - One other spin-off from that is that someone said that they were going to make paint which could tackle smoke problems. So if you had a pub and lots of people smoke in there, you can have this paint which mops up and neutralises tobacco smells. Someone else suggested that a sports bag could also be treated in the same way as the socks.

Neal - And there was research I was reading on the BBC science website the other day where an Australian group has developed a new form of titanium nanoparticles which are doped with another chemical, which I think was vanadium. You may have heard about self-cleaning glass. The way it works is that you have a very thin layer of titanium dioxide on the surface of the glass. This can oxidise chemicals very rapidly under the presence of UV light. Now that's all very well and good for window panes which are exposed to natural sunlight. But this Australian group has shortened what is known as the band gap, which is basically what frequency of light makes these particles active. They have been able to reduce it down to light frequencies very similar to the natural lighting in your bathroom. So for instance, if they can develop this technology further, you basically get paints and tiles in your bathroom that are self-cleaning under your bathroom lights.

Chris - Well wouldn't that be fabulous! My wife would be delighted.

- Does Puerto Rico have the largest radio telescope in the world?

Down here in Puerto Rico we're supposed to have the largest radio telescope in the world. Is that true, and in fact how does a radio tele...

Does Puerto Rico have the largest radio telescope in the world?

Yes that's absolutely true. The biggest radio telescope in the world is the Arecibo radio dish down in Puerto Rico. They essentially work in a similar way to a normal radio telescope but if you look at them, they don't look quite the same. They look just like a really big satellite dish. They work in pretty much the same way. The white surface that forms the big dish acts just like a mirror, and reflects radio waves up to a detector in the centre. That forms an image, focuses the radio waves and creates the radio image that we can look at galaxies with. It also has the added of advantage of allowing us to do radar pings in the same way that a speed camera would catch you in your car. We can actually ping radar off of Saturn or other planets to see how far they are away and also to calculate speeds. We can use the red shift or doppler shift of the radio waves to do this. If you fire a radio beam at Mercury, for example, you can actually see that light that's bounced off one side is altered as compared with light that's bounced off the other side because of the way the planet is spinning. In that way you can see how fast Mercury is spinning.


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