Everything about a spider's web - from the material it is spun from, to the glue that binds it together - is an engineering masterpiece. Built in seconds, each strand in the web is a highly engineered polymer fibre, 10-times stronger than steel. Like spiders, we use a wide range of polymer fibres to build the world around us. This lecture explores how chemistry is trying to mimic the natural world and construct a more ambitious and efficient man-made one.

Professor Tony Ryan
[Tony abseils from roof.] Have you ever stopped and looked around and wondered where all the material that you use comes from, and how it is made?

In this series of lectures we're going to look at how human beings, when they're faced with a problem, get back to the basics, the chemistry and the physics of the world that's around them and the materials that they use and that's why we've become the dominant species on the planet.

Professor Tony Ryan
So, that was exciting.
[Tony stands by desk.] But what was holding me up?
A rope, a rope made from chemicals that are very similar to those that are coming out of my friend Sheena's backside.
[Shot of spider & web.] Her web and my rope are made of long chain molecules known as polymers and these are the real stars of the lecture.

Professor Tony Ryan
They're all around us.
They keep us warm in the form of clothing - we eat them and in fact inside every cell in your body is a little bundle of a polymer that contains the information to make you and it's called DNA.
So polymers are made by joining lots of small molecules together.

Sometimes this looks like magic!
So here I have a collection of monomers. And I'm going to pour them into my reactor, it could be a factory, it could be a spider.

But they don't join together to make a polymer until I do something special.
And my friend Fritz here is the expert.
[Fritz & Tony stand in front of desk.] So Fritz, you come round this side, I'll go this side and he brought the spiders, so he's the 'Spiderman!'

Now, what we're going to do is we're going to pour the monomers into the reactor and there they all go and they've not made a polymer yet.
We need to do something special - we have to add a catalyst.
So Fritz please, put the copper catalyst in.
[Fritz drops catalyst into container.] We gave the box a shake and here we have a polymer chain comes flying out, not all of the monomers get joined up.
You have to keep it shaking to keep the reaction going and all the monomers have gone.

We've made a beautiful polymer chain.
Thank you very much, Fritz.

Applause

Professor Tony Ryan
[Shot of spider.] So the spider that's sat here making polymer that we're winding up is taking a fluid from her body and squeezing it out to transform it into a solid and Bipin and I are going to do an experiment that looks just like that.

[Shot of oil/water container.] We're making a polymer that's quite similar.
So he's taking a liquid, in this case, an oil and that has little molecules in, called monomers.
And then he's putting another liquid on the top, in this case it's water and that has a different monomer in.
And at the interface we get a polymer formed.
So just to show you what's happening, we went to St. Wilfred's School and made some children play the parts of the molecules.

So here they are. [Tony looks up at screen showing children acting out molecule parts.]
The blue ones at the top are running round, just like the molecules in the solution and the yellow ones at the bottom are doing the same, but when they meet at the interface, they join up, yellow/blue, yellow/blue, yellow/blue and make a polymer.
[Tony pulls thread from liquid in container.] So Bipin's going to pull a polymer out from the interface, I'm going to try and catch it - which I have.
Thank you very much - and we're going to raise it gently ... some big bits in there, looks like a shark's laid an egg halfway up my polymer chain and right from the interface, look here, we can see a polymer being formed and those molecules are joining up as it's reaching all the way to the top of the ceiling.[Shot of thread stretching up to roof of lecture theatre.]

We're going to get about 10 metres of nylon out of those solutions.
So this polymer has its crystal structure displayed on the screen and I'll explain to you where that crystal structure came from later.

Wow, and thank you - that great video piece was recorded at St. Wilfred's school and here are some of the children who took part. Thank you very much indeed. [Shot of St. Wilfred's children in audience.][Applause]

Give us a wave![Shot of kids waving.]

[Shot of Sheena the spider on table.] Now Sheena here is making silk and that silk's slightly different to the nylon.
It's made from the same elements - carbon, hydrogen, nitrogen, oxygen.
But they're put together in a slightly different way and that means that their properties are different, so I want some volunteers to help me test mechanical properties.
We'll take this boy here from the front and the young lady in the black 't' shirt and the glasses and the boy sat behind her in the yellow.
If you three would come down and join me.

[Tony shakes hands with children.] What's your name? [Charlie] - Charlie - [yes] - pleased to meet you, Charlie. And what's your name? Jessica? And John.

Right, me and Charlie are going to test the mechanical properties of this soft stuff, it's called rubber.
Now I need you to hold on, you might need to hold on with both hands. [Tony & Charlie hold ends of rubber strip.]

Professor Tony Ryan
We don't have to pull hard, because it's really easy to stretch.
Now don't let go, because it snaps back, OK, because it's a big elastic band.

But you can see how flexible it is.
Thank you very much.
Just wait there for a moment.

[Tony & Jessica hold ends of material.] And we're going to look at this material - Jessica.
Polyethylene, let's pull, slowly, pull slowly, slowly, oh!
Right, that wouldn't have been very good to come down from the ceiling on, would it?
Thank you very much.

And what about this material? This is more like my rope.

[Tony & John pull at each end of rope.] It's flexible, like the rubber, but when we pull - it doesn't stretch at all - right.

And it's because the properties are very different. Thank you all very much.

[Downshot of lecture theatre & audience.] [Applause]

Professor Tony Ryan
But we couldn't rely on those pulling tests and describing the properties if we're going to manufacture something that we can use safely - especially for someone as big as me to come down from the ceiling. We need to know exactly what the materials are and we use one of these instruments to accurately measure the mechanical properties.
[Shot of machine.] So we have - Anna here has loaded up some nylon and some silk into this Instron machine and we're going to start pulling them apart and down here you'll be able to read what the properties are. [Anna & Tony stand at either side.]

[Shot of graph on screen.] So if we start the test - so we're starting to stretch and this graph shows you what the force is and it goes up and up - and up - and up .... off screen and then eventually one of the polymers is going to start to break.
Right, you see the nylon fibres are popping, one by one, and the force is coming down and the silk is still going strong.

Now if I hadn't told you what the result was, what would you have expected?

Right, you'd always think that nylon's going to be stronger than spider silk, wouldn't you. Yeah? I mean I would have, if I hadn't done the test an hour ago. [Laughter]

Professor Tony Ryan
Right, and what's that difference?

Well, in the nylon you saw that the molecules were all stretched out and in the silk they're all tangled up and I want to use all your hands to do a demo. So all get your hands out please, wave them in the air, so I can see them, right.

[Audience shots intercut with shots of Tony/hands together.] And I want you to put them together, just with your fingers, like this. And this is like the polymer chains that are lined up next to each other. And I want you to pull and look, your hands pop apart, don't they? You can just slide them past each other.

But if you interlock them like this, these are like the tangles in the nylon.
And these are also like the tangles in the silk and when you pull them past each other they don't go, do they?
And the spider engineers more of those tangles into her silk than we can engineer into the nylon.

So let's say I wanted to run down from the ceiling on some of this web. Would I be able to do it?
No, because there's only individual threads.
[Rope-making machine model is brought in.] If I want to make a rope, I need to put more and more material together, so with one thread we'll hold one gram and I need to hold a hundred kilograms - I need all of those threads to be together and the way we do that is to make the fibres effectively fatter by making a rope.
[Oliver & David take up places.] So Oliver and David who are up here - have already been in to learn how to make rope.

So if we take up our positions, boys, thank you very much for coming down. And I am going to get in the middle.

Now you remember what to do with the turning? [Yep]. Yep.

[Shot of spider.] So this is really complicated, isn't it, compared to what old Sheena has to do. Are we ready?

[Shot showing rope plait being made.] So I can see that there are some girls in the audience with long hair. You've made plaits, right - and that's exactly what's happening here. The plait is being made with all this rope and these things are called rope walks for this very reason, that Annie's walking along the rope.

Thank you very much indeed, well done. [Applause]

Professor Tony Ryan
[Shot of Sheena.] So we can see how to make nylon, by the nylon rope trick and we can see how to make a rope by twizzling it all together, but this spider would drop from its own rope and it gets everything it needs from eating wasps and flies and other things that go into the web.

[Shot on screen of wasp trapped in web.] And the wasp contains all of the elements that she needs to spin her web.
So inside this spider and this spider - and this spider, in that belly is enough silk to make four hundred metres of her web. [Shot of spider in glass container.] That's a fantastic length from something so small.

So, I want to give you a feel for what four hundred metres looks like. So there are four of these that are being passed round [shot of children passing round spools of line] , each, and keep, you need to pass 'em quickly, just so you can feel how quick, how much silk is stored inside this tiny little spider.

So what about its fantastic web?
When she goes to make the web and actually this is, this one's Fred, I think, in here.
He puts special dabs of glue down and that glue is made from the same silk that the strong fibres in the web's made from. [Shot of spider in glass case.]

So a little dab of glue goes down with no pulling on the thread and then to make these load-bearing sections, the thread gets stretched and then to make the circular bits of the web, which you can see up on the screen, the spider does something completely different.
He makes soft fibres - and those soft fibres are coated in something that absorbs water.
So let's say I'm a wasp and I'm running towards a hard web and I run across, boing, bounce off and I'm not going to get eaten - that's no good for the spider, because as well as being the home, this web also has to be a source of food.

So these fibres stretch slowly and absorb the energy and so the wasp gets wrapped up and this clever little spider extracts all the elements she needs to make that ever important silk.

So this whole construction, load bearing, reminds us of something that human engineers do.

They need far more than the four hundred metres of web that are out with you now. Took you an enormous long time to pass that out.

[Suspension bridge model is wheeled on.] Now this suspension bridge has all the same features.

It has load bearing cables and they're anchored. [Shot of cables.]

Remember, the spider anchors by putting a little dab of glue down. Human beings have to drill holes and put big bolts in.
[Tony points out cables.] These fibres also bear some strain - these are nice and flexible, so if the bridge rocks or moves in the wind, it can take the strain, just like the soft fibres that we saw in the spider's web.
[Shot of Golden Gate Bridge on overhead screen.] Now, there's the Golden Gate Bridge up there and we've even started to make bridges from plastics, just like we have the construction from the spider, of this fantastic polymer.

So you've seen all the evidence now, it's time to get your voting cards out. [Audience reach for voting cards.]

So who's the best engineer? Red for the spider, green for the human? Well it's not quite unanimous, but there's far more red than there is green. It's a bit like being at a Man United game and me being a lad from Leeds - that's not such a good thing!

So the spider wins and just before we leave for the break, I want to give you a word of warning.

[Overhead screen shows black-and-white archive film footage of suspension bridge collapsing.] Sometimes, human engineers can get it wrong.
We draw inspiration from nature, but we often break our design rules and this can mean disaster.
The engineers that built this suspension bridge got their sums slightly wrong. They should have taken a leaf out of Sheena's design book.
Remember if we're going to use nature, we have to obey the rules. [Applause]

Professor Tony Ryan
[Tony & assistant bring in sheep.] Throughout history we've relied on nature's polymers for our survival.
We've kept flocks of sheep for thousands of years and used the wool they produce to keep us warm, but the polymers we use aren't just from animals.
They are found in the plant kingdom too.
Cotton is farmed for its polymer and cellulose can be spun into fine threads that can be used to make everything from cinematic film to fancy undies.

About a hundred years ago just about everything we wore was made of these two natural polymers. [Shot of sheep.] But how does this compare to today? How much ... [Laughter] ... uncooperative sheep's wool do you think you're wearing? Right?

[Tony looks at clothing worn by members of audience.] These guys have synthetic fibres, nylon. They also have cotton and I'm looking round - this young lady here, stand up, give us a twirl, yeah? There's some lycra, some elastane in that top that makes it nice and stretchy.
And over here, this lovely shirt - let me just have a feel.
That's made from polyester.
[Boys wearing grey school jumpers.] And then these two boys down here, they have the classic school itchy jumper. [Laughter]. Right. And they're made from an acrylic polymer. And that polymer is kind of a throwback to the first synthetic fibres and they were made by wet spinning.

And I'm going to show you how wet spinning works now.
So Annie's bringing on a polymer solution and a big tray full of water. [Table with polymer solution in container is wheeled in.]
[Tony holds up solution.] Now we're going to make the fibre by taking the solution and you can see it is a solution - it's a liquid and we're going to extrude that liquid under water and the solvents exchange and the polymer doesn't like the water, so it precipitates and becomes a solid. [Shot showing process.]

I can even pick these fibres up.
They've made something that looks like the cloth you might use to clean up in the kitchen. Thank you very much.footage in room outside lecture hall/Tony stands by machine

[Footage on overhead screen of spinning factory.] But we don't make that many synthetic fibres these days by wet spinning.
Nowadays we use melt spinning and that relies on pumping a polymer through a hole, very much like the hole in the spider's bum to make a solid line and then we can use that solid polymer to do all our weaving processes.

How do we know what the structure of the fibre is?
Well outside of here, because the model was just too big to bring in to, to show you, we have an X-ray machine and I'm going to show you the X-ray machine. [Footage in room outside lecture hall/Tony stands by machine.]

[Tony demonstrates process of machine.] So here is an extruder - that's this thing up here.
And we've put the polymer chips in and the polymer chips go down a hot tube and the molten polymer comes through the spinneret.
Just think of this as being the spider's bum.
And then we take the polymer down in a line and then the synchrotron, which is a massive machine, about the size of a football field, produces X-rays and the X-rays come through, interact with the polymer fibre and are scattered and rather than showing you the detectors, what we've done is we've played back what those detectors see on these TV screens.

So this TV screen shows you what the detector sees, about the size and shape of the crystals.

And this TV screen tells you where all the atoms are, so we can get the crystal structure.
And eventually we can build a model like this one, of the polymers rattling around, to become crystals.

[Tony walks back into lecture theatre.] So I'm going to go back in now, because you don't have to use X-Rays to get crystal structures, to see crystallisation.
So when we look under the microscope - I'm just going to fiddle with the temperature.
So there's the crystal structure of the nylon and now, oh look, my polymer's about to crystallise and you can see up on the screen, the crystal growing through the molten polymer.

That's what happens when we do the extrusion process to make fibres. We can tell where all the atoms are going. [Process is shown on overhead screen.]

So it's finished crystallising.
[CU shot of molecules on screen.] So what happened to the molecules during that? Well they started to rattle around and all the long chains rattle so that they start to fold up.
And there it's kind of jerky, because this is a real-time computer simulation of what happens to a single polymer molecule whilst those crystals are growing. And you can see they all fold up.

So we've learned a fantastic amount about crystallisation. In fact, this is a subject I do research on and today I rang up my research group. [Overhead screen shows film footage of Tony's group.] And they're out in Grenoble, working on another synchrotron. And they were really excited, not because I was giving the Christmas Lectures - because they actually made a discovery today, about how crystals start, so Ellen's giving it the big thumbs up, because that's the best scientific result she's had in a long time and the guy you can hardly see in the middle is one of my best mates, Wim Bras.

And we worked together on this synchrotron to try and understand what the molecules are doing, all the time they're being processed.

So, we've learned a lot about how these fantastic molecules crystallise.
But all the polymers are intrinsically colourless.
But if we look around today in the audience, you're all wearing bright colours, fantastic colours.

Even the school uniforms have interesting colours, right. When kids went to school in the 1850s, they didn't have all these bright colours.
It wasn't until William Perkins, who was an organic chemist, invented mauve, the dye, that we got a range of bright colours.

Prior to that only rich people could wear bright colours, because to make the dyes you had to crush up beetles, or find a tree that exuded sap that was exactly the right colour.
But now, everyone can have colour.

And there was an explosion of this. [Tony holds up mauve 't' shirt.] This mauve colour was the thing to be seen in, in the 1850s. Everyone wore it because it was the only colour available! [Laughter]

[Tony holds up velvet top.] Now they wanted me to do the lecture in this, I don't know whether I quite approve.
But these kinds of garments that are brightly coloured have only been available because we can develop molecules that have specific colours and we can make them stick to the fibres we want.

[Table is wheeled on.] Now we've had some volunteers already to help us with this dyeing experiment.

[Flag is held up.] Now, a couple of weeks ago, my mum made a flag and we can see the flag, it's white, right?

And here we have a murky liquid.
So we're going to put the flag into the murky liquid.
[Annie puts flag into glass container.] Annie has to do this because it's hot and we, we can scald her, we don't want to scald the volunteers, right, it's about seventy degrees.
And she's going to pull it out and our volunteers will rinse it - there's nothing dangerous about this at all.
So you need to give it a good dab, squidge it around and then when you hold it up, which you can do now, hold it up the right way around and ... [hums 'Land of Hope and Glory] ... [Children hold up flag with Union Jack colours.]

[Applause.]

Right, we made this flag just by dipping different fibres into a bath that contained different dyes.
And the blue fibres stuck to where the blue fibres, the blue dye stuck to where the blue dye was supposed to go and the red dye stuck to where the red dye was supposed to go and the white was completely unaffected.

[Tony holds up different coloured rugs.] Now this process of making something that's white and then colouring it afterwards, actually helps in industry.
Because you can just run your carpet-making factory, making white carpet and then, let's say that blue and red carpets are the current fashion and everyone wants blue and red, you can dye them afterwards using exactly the same technique.

So this carpet, which has three shades of one colour and two shades of another, has fibres that are specially modified on their surface to interact with those dyes that give you blue and red.
So they take those up and they leave the others behind.

Now, carpets are great, but they're on the floor, right, and what happens to them?

[Tony empties contents of vacuum cleaner on to carpet.] Well, they get covered - all this stuff get sucked out.
So if we grind it in, right - [laughter] - you can see what happens.

[Speeded-up shots of people walking over carpet.] Now when you guys came into the lecture theatre, you came through a doorway and a month ago we put a carpet down in the door.

And the carpet was originally this colour and as it got walked over - then out came this writing. [Tony holds up section of carpet with writing on.]
How did that happen?
Muddy feet go over it, it's yellow to start with and all of a sudden yellow writing comes out of a dirty background.

In actual fact there's as much dirt in the clean part as there is in the dirty part.
And all the mums and dads upstairs are wondering where they can get a carpet - [laughter] - like the clean part.

Well what happens is, these fibres are round, like this one at the bottom and the round fibre acts like a magnifying glass.

[Shot of perspex model showing word 'sporco'.] Are there Spanish speakers in the house?
And what does 'sporco' mean?
It means 'dirt' - right, so you can see the dirt through the lens.
And so the carpet manufacturers thought, well if we can make the fibres scatter the light, you won't be able to see the dirt that's behind.
So they put something in that made the image of the dirt become a little more blurred.

But that didn't help with the long-life properties of the carpet.
So then they developed a fibre that rather than being round was like a 'y' shape and if I can just, there, you can see you get multiple images of the dirt from this, so the light's being scattered and you actually see more of the fibre than you do of the dirt.

But the solution to the problem which is now you can hardly see the dirt at all, right, there's no 'sporco' to be seen.
And in here the fibres have holes running down the middle.
So this fibre isn't a fibre at all - it's a series of tubes of air and those tubes of air scatter the light.
[Tony reels out roll of bin liners.] So we've seen how there are lots of fibres that are made from polymers, but the majority of polymer gets used to make film and we see it everywhere.

Professor Tony Ryan
Just hold on to that for me, just hold on to the end, tightly, yeah.

This is the way we normally experience polymers.
It's bin bags, it's sandwich wrappers, it's all of these things.

A hundred years ago there were no man-made polymers.
Now a balloon's going to go to the edge of space made out of exactly this material and I'd like to introduce you, if you could just drag them in, to the balloonists, Colin Prescott and Andy Elson. [Balloonists enter lecture theatre wearing pressure suits.]

Hello, Colin, hi Andy. [Applause]

So wow, this is some of your balloon.

Andy Elson
This is it, this is the fabric.

Professor Tony Ryan
So how high are you going to go in this balloon?

Colin Prescott
We're aiming to go about twenty five miles above the earth - [wow!] - which is about five times the height of Mount Everest and if we do it, we will break our record, which has stood for over forty years, set by two US astronauts in 1941, highest balloon flight in history and we're going to have a balloon that's about ten times the size of theirs, forty million cubic feet, higher than the Empire State Building [wow] and that will be erm, some balloon, I think you'll ...

Professor Tony Ryan
Aha.
So you're going to go twenty five miles up in a bin bag, right?! [Laughter] Basically, yeah.

And why did you choose polyethylene?

Andy Elson
Well the great thing with polyethylene is where we're going it's going to be, we'll go through about minus seventy degrees centigrade.
Gradually when we get really high, up to about a hundred and twenty thousand feet, it gets a little bit warmer, it's oh about minus thirty, minus twenty.

[Shot of Andy holding polyethylene sheet.] But polyethylene still stretches so the balloon can have some give in it [right, excellent].
We start off with a really tall balloon, with just a little bit of helium.
As the balloon climbs, the helium expands and we need the polyethylene to be able to move and give, otherwise it would tear. [Right].

Professor Tony Ryan
So there are lots of dangers for this balloon fabric, then. Right from the temperature and the pressure ...

Colin Prescott
Well the dangers aren't so much. [Shot showing structure.]
I mean most people think you're going to have bird spikes, you're going to get birds pecking into it and in fact that's not going to happen - or a meteorite's going to fly through it, that's not going to happen either.
But on the other hand if we went through very severe wind ..., I mean this is such an enormous structure, I mean it's about ...

Professor Tony Ryan
Right, this is wind going two directions.

Colin Prescott
Yeah, two directions at different speeds.
I mean it's about nine acres of this polyethylene you've got in the balloon and that could just destroy it and that is a danger.

Professor Tony Ryan
And what protection do you guys need to go twenty-five miles up in the air?

Andy Elson
Well basically we're going to be wearing space suits, like the one over here.

Professor Tony Ryan
Oh, I thought that was one of our audience.

Andy Elson
[Cut to audience/space suit 'sits' between Fritz and boy in audience.] That's actually a suit that we've been using for our training and ... you see, the suit that we wear on the day, we don't want to bring it around and get it kicked about and you know, worn out and that one's been on Mir twice - there's a lot of history with that suit.
And the suit keeps our blood from boiling.
Above sixty-three thousand feet there's not enough pressure to keep a human being alive. And really space starts at about a hundred thousand feet and we're well into space ...

Professor Tony Ryan
[Group stand with polyethylene sheet.] Wow, excellent - so earlier, you all thought that spiders were the better engineers, but what do you think now?

Is it the humans with their fantastic carpets and the bin bag going up to the - [laughter] - or is it the spider? So vote red for spider and green for human.

[Audience hold up score cards.] Yeah, well it looks like we have a bit of a draw on our hands here.
I think that I've shown you that we're getting better than nature and these guys certainly have, so I just want to thank Colin and Andy for coming along and best of luck with the trip and in the last part I'll be asking whether we can learn anything more from nature.
Thank you. Applause

Professor Tony Ryan
So far we've looked at how nature makes polymers and how we develop the ability to make our own.
Does this mean that we are better than nature?
Is there anything left for us to learn?
We look again at Sheena, a chemist extraordinaire.

When she's finished with her web, what does she do?
She eats it.
She takes all that polymer back into her body and re-processes it to make a brand new web.
Takes an old web and makes a new web.
What do we do with the materials we've finished with? [Tony stands in front of rubble filled tarpaulin.]

[Children bring in rubbish.] Well I asked you all to bring all of the rubbish you'd generated over the past twenty four hours and here it is and the last two have been brought in by, what's your name? ... Alex, who's playing the part of a bin man [Kate] and Kate who's being a bin man, please chuck your rubbish on. [Rubbish is tipped on to tarpaulin.]

Professor Tony Ryan
Whoa!
Right, well thank you very much for chucking that rubbish in. [Applause.]

So what's in here, what sort of rubbish have you guys generated?
Well you've eaten lots of these, right, some sort of snack food.
A packet and a half a day are the statistics, I don't know how much good that's doing you.
And you've also drunk lots of these, right.

So we're going to weigh all this rubbish now and find out how much there was. [Shot of tarpaulin being hoisted up.]
Up it goes - I need to run round.

And how much have we got up there?
Twenty seven kilos.
Two hundred of you have generated twenty seven kilos of rubbish.

And what happens to it?
Where does it go?
It goes in a landfill.

So you had a hundred and fifty grams each today.
Each year, each one of you generates fifty-five kilos of rubbish.
That's a fantastic amount.
It's nearly your average body weight.

In your lifetime you dispose of four tons of plastic material and it gets buried in the ground.

That's amazing!
Four tons is a double decker bus!
Just from you and it's all oil that's getting buried.

[Tony taps a plastic cola bottle.] So what can we do about recycling?
Can we turn these into new bottles?
And the answer is 'no' and I have a couple of volunteers who are ready to help me demonstrate why that's the case.

So we've already wired 'em for sound, so down you come.
And out comes the block that you're going to use to demonstrate.

[Children stand with Tony.] So what's your name? [Anna].
You're Anna, and your name? [William].
Hello William and Anna.

Right, what I want you to do is bash things.
I think - you take that one and you take that one.
[Shot of polythene stick.] Now this looks like a candle, but it's made from polythene. It's the same material as the candle. It's just a - molecules are a hundred times longer, so let's give it a bash, the polyethylene one.

OK, now, let's say that we've recycled the polyethylene many times and the molecules get shorter and shorter and shorter and now William's going to give them - give it a really good bash, William.

Oh look, keep bashing.
And what does he end up with?
A piece of string, right.
Thank you both very much indeed. ...

Professor Tony Ryan
So we can't make the same thing again, unlike our fantastic spider.
[Tony holds up cola bottle.] If we're going to recycle PET, what we have to do is we have to chop it up into little granules and make it into fibres.
It turns out that the polymer that's needed to make a bottle has to be about twice the molecular weight of a polymer that's needed to make fibres.

[Tony walks over to machine and pulls out fibre.] So we can take PET granules or chopped up PET and extrude it to make - this is a kind of a thick fibre.
I don't want to get too close, 'cos it's rather hot, right.
And we can make fibres from chopped-up soft drinks bottles.

Thank you very much for that.
So, how many of these do you think it needs to make, let's say, a PET polyester fleece?
Any ideas?

[Table with scales is wheeled in. Tony holds up jumper/balances jumper & bottles on scales.] [Four hundred]. Four hundred, OK, well let's test that.
So here we have a nice fleecy jumper and we put it in the scales and these are already too heavy, right.
So we've got about ten bottles in here and ten of them is enough to make a PET jumper.

These weigh about twenty grams each and this jumper weighs about two hundred grams.
So is a fleece the end of the line for that polymer?

[Shot of bottle of oil.] You see they're all made from oil and the oil is where they came from, so we took oil, which is small molecules, and then we built it up into a very long molecule and then we reprocessed it, we made something else, we recycled it into something else.

You see, when I was a lad we didn't call it fizzy drink, we called it 'pop' and it came in a glass bottle and you didn't get it from the supermarket, you got it from the newsagents and you paid a deposit on the bottle and when you'd finished with the bottle, you took it back to the shop and got your deposit back.

It was actually a good source of spending money.
You could go round and find these bottles and go and collect someone else's deposit.
We don't do that any more.
And the reason for that, well there are many reasons for it, but the main one is the energy required.

So it turns out that there's less energy needed to make a brand new bottle than there is needed to collect bottles, take them back to the factory, wash them with hot water, sterilise them and fill them with a new drink and bring that back to the shop again.

[Screen showing landfill process.] So all of this - oil that's been converted into various goods is now buried in landfills.
So all that rubbish that got taken away will end up underground and I suspect that when the oil runs out in a hundred and fifty years, that some of you people will be setting up businesses to mine landfills.

We're burying a very important chemical feed stock.
And is it the end of the line?
We can go from bottles to fleeces and the sad place that a polymer ends up is as one of these, a road cone. [Tony holds up road cone.]

[Sheep is led in.] So maybe the answer's in farming.
Oils, fossilised.
Maybe this is the way forward, right?
This sheep is farmed for her wool, but what we could do is we could take the gene that makes the silk from the spider.
We could splice that gene into the sheep and then get two harvests from the sheep.

One harvest of wool and the other harvest, the s.. protein from her milk - and Fritz, who you met earlier is trying to do exactly that.So that's one way we might be able to harness nature and use carbon ... carbon dioxide and sunshine to make engineering materials.

But the other way is to grow new materials.
Thank you very much for the sheep, she's been very good today. [Applause.]

We could also take something that grows in a field. In this case corn or wheat.
We can take the starch that's in the corn and wheat and ferment it, not to make bread or beer, but with special bacteria that make a compound called lactic acid and you all, you all know what lactic acid does, it's what happens when you get a stitch.

[Tony holds up plastic knives & forks.] We p... the lactic acid and then we can make an engineering material and it, it's amazing, but knives and forks like these can be made biodegradable.
That environmentally friendly organisation, known as the US Navy has developed knives and forks made from polymers that are effectively grown in fields and when you chuck them overboard into the sea, they dissolve within hours.

You see, nature's been around us for millions of years and if we're to survive and not destroy our environment, we could do a lot worse than learning from nature and learning how to harness its power.

Applause/music/credits roll