The trainer is a miracle of modern science. The average pair lasts just six months, but in that time, they will have run 3,000 miles, absorbed 400 litres of sweat and withstood 400 tonnes of impact. How they survive this battering is down to some miraculous chemistry that lurks beneath their flashy skin - a hidden world of impact cushioning gel, moisture absorbing insoles, and breathable foot-hugging coatings. So tune in and explore the chemistry that propels us around the planet.

Professor Tony Ryan
[Tony jogs into the lecture theatre.] So today I'm going to talk about something we all have to do in our lives and that's travel.
Transporting yourself somewhere today can be done pretty much any way you want, but perhaps the simplest method is using the power of your own two feet.

Now what you're wearing on your feet isn't always the fashion accessory you think it is.
Often there's lots of excellent engineering in there.

So, I have some special trainers on. In fact they're so special I can show you what's inside them. [Tony takes one trainer apart.]
So on the outside are the laces and often they're quite high-tech, with the loads they need to take, and then there's the tongue and that's padded so it doesn't dig into you - and then there's the insole and for me, this is especially important, the insole's got special chemicals in so that it doesn't pong too much - [laughter] right.

And then there's foam here and this stiffening bar and a different foam and an air bag.

So we can see this air bag and these special devices that stop it from collapsing.
Now there are subtle differences in every trainer, depending on its design and let's start from the bottom.
It's the sole that's important.

[Footage of climbers on overhead screen.] Now we took some VT. tape of the lads out climbing last Saturday. In fact Eric's one of them, he's sat up in the back and he very kindly fetched his climbing boots in.
Actually those boots there are mine and I don't know whether they've slipped the piece in where I actually fall off, right.

And why did I fall off?
Well I fell off because the grip didn't work.
So to help me take a look at grip we're going to need some volunteers and those volunteers all have to be fifty kilos in weight and have size 5 feet.
Oh, look at all those hands go down! [Laughter]

And where are the six hands that are going to stay up with the right sized feet over here?!

[Group file in.] ... Come here.
What's your name? ...
Right, pleased to meet you.
I'd like you to stand on here.
[Girl steps onto tilting table.]
And what's your name?

Can you just use that handle to move her up in the air please.
No, you don't have to do it too quickly, keep coming, up we go, up we go.

What angle are we getting to down here?
We're up to ten degrees, whoa, and who's going for a slide![Laughter]

Down she comes, well done!
Thank you very much indeed.

[Applause.]

See, those bowling shoes were on the same material that's used to make non-stick frying pans, so you wouldn't expect her to go very far, would you, in terms of the height and the next pair, what's your name?

Pleased to meet you, come on, let's get you on this grassy slope here. [Second volunteer steps on to the astro turf.]
Well it's not a slope yet, but it will be soon.
OK, on you go.
These are your trainers, aren't they? [Yep].

And what's your partner called? [Rebecca].
Rebecca, come on, out you come.
So I'm going to move the handle up and down.
And up she goes, twenty degrees.
Do you want to just stand round there and make sure she doesn't topple off?
That would be a big help. Thank you.

So don't lean on her, just use her for balance.
How are you feeling at thirty degrees? Good?
Whoa, off she comes, about thirty five!
Well thanks a lot, girls [applause] - you have thirty-five degrees there.

[Third volunteer comes forward.] Oh wow, but I recognise those shoes, they're a pair of rock climbing boots like these, they have special soles, designed for this rough surface, so out you come.

What's your name? [Nikita].
Nikita, come on, on you get.
Hold my hand as you get on, because you know they're not very stable, these.

Turn round towards me, Nikita, don't worry, it's going to be fine, just move back a touch.
And your name? [Rachel].
Rachel, look, I'll tell you what we have to do.

We have to move it up and down, gently like that, OK?
Right, you can do it this time.

Just down there, move back a bit.
You feel great, don't you! [Yeah].

You're not going to fall off at all, are you!

This is sticky rubber.
What's happening is it's been bent by all the protrusions that are on this sandpaper and that's there to simulate the rock, OK, keep going.

What angle are we at now?
Thirty-five, forty, you want to fall off, but it's not because you're losing grip, is it?

Let's stop there for the moment, just come, walk down a little.
I'd like you to turn round ... like that, just balance on your fingertips.
OK, come on, keep on going.

All the way up, all the way up.
Does that feel good? [Yeah].

I'll tell you what, Eric'll take you out rock climbing next Saturday if you want to go! [Laughter.] [OK then.]

Alright.
And where have we got?
We've got all the way out to fifty degrees.
Thank you both very much indeed. [Applause.]

[Tony stands behind table. Assorted trainers lie on the table.] Let's say the soles of your shoes were made out of treacle.
Now, you'd stick, wouldn't you, if you had treacle on your feet, but when you were tilted up, what would happen is the treacle would just slide, so the forces making you grip are a combination and they're a combination of the two surfaces and the rubber itself.
You see we'll find that this contact between rubber and another surface is common to nearly all forms of modern transport.

[Footage of rubber plantation.] So, natural rubber is harvested from trees. I've got some here.
It's that milky fluid you can see dripping into a cup, so here's rubber latex.
That contains the material that eventually makes this.

And the American Indians were the first people to start using it.
What they did was they learned how to make the first wellington boots, by dipping their feet in there - right, because the polymer goes onto your foot and, and the latex dries, so you get rubber, like this.

[Tony holds up a polymer chain.] Now the rubber's a polymer chain and it's all tangled up.
That's how it wants to be, all tangled.
And what happens is, when you stretch it, you untangle the chains and then when you let the tension off, then the chains re-tangle again.
[Shot of a bowl of spaghetti.] In fact, it's just like this bowl of spaghetti.
In here are a load of chains that are all tangled up.
So if I dig my fork in and lift - I don't just get one, I get all of them.
But you see, when I let, when I let go, it doesn't spring back to exactly the same place.
Some of the chains slide past each other.
So you get what's called a permanent deformation.

Now if your shoe soles had rubber on where the material could slide past, that would be just like having treacle.
It would just slip.
It wouldn't be any good for you at all and you don't want this in your shoes or a car tyre.

And vulcanisation, the cross-linking of rubber was invented in 1839 and that started the whole industry around rubber.
And vulcanisation creates a tangled web by joining the strands of spaghetti together, so that when you stretch one chain across the join to many other chains, you have to stretch them too.

So they all jump back into exactly the same shape once you take the tension off.

Now I'm going to need four volunteers to help me.
These two lads down here had their hands up pretty quick, the girl in the black 't' shirt and the young man in the blue, is it a blue shirt, blue fleece? OK, we'll use you four.
I'll just nip round.

[Tony stands with the four volunteers.] I want you to, right, we'll take you two together, at the back here.
So I'll just stand there like that and you two together, further towards the front, facing the cameras, please, you come here.

I'm going to give you a snake, you're not frightened of snakes, are you?

Are you sure? [Yes!]

Not even snakes that are this big?
It won't bite, OK.
Now I want you to turn and face each other, just hold it there please. Good lad.
And I'm going to run round the other side of the desk, OK, you need to be a bit closer together, OK, a bit further apart, perfect.

OK, I'm going to run round the back - to direct what you do.
OK, so the front two, will you pull on the snake, how far does it stretch? [Children pull on 'non-stretchy snake'.] Not very far at all, OK, that's fine.

Right, you two boys at the back, can you pull? [Boys pull on 'stretchy snake'.] [Laughter.]

Pull, pull, keep pulling, don't let go, whatever you do! [Laughter.]

OK, you can come back in now.
Come, I'd come back in slowly, if I were you.
OK, give me back the snakes, thank you very much. [Applause.]

So, what happened when this straight snake got stretched was the molecules all got stretched.
So the molecules are all coiled up in the snake originally and then the molecules all stretched out and there were big lengths of chain between the links in the bendy snake and it'll store lots of energy, right.

But there's hardly any distance between the chains in this snake that's really hard, because there's hardly any chain to bend and stretch between the links.

So I know you've been flicking your rubber bands at me, right [laughter].But what I'd like you to do is take your rubber bands out now, so just put them on your thumbs, stretch them apart, OK.
So now what I want you to do is put it on your lip - [laughter] and stretch it on your lip - I'll see you later, right!
So stretch it on your lip. Feel it get warm?

Right, let it back in, slowly.
Feel it get cold?
Right, it's amazing that, isn't it.
It gets hot on the way out, cold on the way in.
[Graphic/simulation of rubber band on overhead videoscreen.] You see, inside the rubber bands are a big collection of jumbled-up polymer chains that are chemically linked together and when you stretch them out, they have to lose some energy.

You see they're dancing around, so the molecules are all dancing around and you stretch them and they actually can't dance that much any more.
And so they give you some energy back.
You feel it as heat and then when you un-stretch the rubber band, it gets cold, because, and it should be on its way back in now, the rubber band, the molecule, it goes from being unable to dance, to dancing again, but it needs to get that energy back and it takes it from your lip.

And what's weird about rubber is that it contracts when it gets hot and expands when it gets cold and that's not the way that things normally behave.

And it's this unique property that makes it grip the way it does.
You see it's not just the bottom of our shoes where grip's important.
[Videotape shot of Formula 1 cars on track.] If you're travelling at two hundred miles an hour, like these racing drivers, you want to be sure you're going to stay on the track, so you can see the car that these tyres came from and someone's going to come down and help me have a feel of these tyres. [Tony compares tyres in lecture theatre.]

OK, have a feel of this one.

Does it feel sticky? [Yeah].
Yeah, it does, does it feel very sticky? [Erm, no]. [Laughter.]

OK, very good!
Right.
And it's cold, isn't it? [Yeah].
Have a feel of this one.

Do you think this one's going to be cold? [No].
All right we'll open it up now.
Just take your hands off a moment.
What's your name, by the way? [Patrick].
Right, Patrick. OK, have a feel of that one. Wow!

It's warm and it's sticky, isn't it? It's amazing!
Do you think that's sticky? [Yeah].
Right, and why do you think they keep them under the hot blanket? [So you don't have to heat it up].
Right, so you don't have to heat them up when you go out on the race track.

Thank you very much, Patrick. [Applause.]

You see, the stickiness is because of the way we've put the cross links into the rubber.
Racing tyres don't last very long.
They could maybe get you down to the shops and back, if you drove like Eddie Irvine, right.
Normal car tyres are a little bit different.
They're a compromise between grip - whereas these are only grip.

These'll only last for at most a hundred miles, whereas the cars your parents drive, you need those tyres to last for tens of thousands of miles, especially if you're as cheap as me and you don't want to replace them very often, right.

So real car tyres, road tyres, they're a balance between grip, holding onto the road - rolling resistance, which is how much petrol you'll consume and longevity, which is how mean you are, right.

So we've seen how Formula One tyres and trainers are based on rubber for their grip and we know that deforming the rubber makes it hot - you know, your feet really do get hot if you're running.
That's because of all the energy that the rubber molecules are dealing with.

But what happens if your trainers get cold?
[table is wheeled in/Tony investigates liquid nitrogen container/dips rubber glove into container.] So, in here we have liquid nitrogen.
It's a minus a hundred and ninety-six degrees centigrade.
And here we have a rubber glove.

So, we're going to take the glove and cool it down, OK, it's changed, hasn't it?
It's not rubber any more. In fact, what I can do is ...[glove is crumbled up]... crumble it up, just like glass.

[Close-up shot of pieces on the floor.] So sometimes, this wonderful material behaves like a liquid and sometimes it behaves like a solid.
And in a few moments we're going to take a look at the differences between liquids and solids and why don't you all give me your rubber bands - now! [Laughter.]

[Children throw rubber bands at Tony.] [Applause.]

Professor Tony Ryan
[Tony sits on a bouncy ball.] So we've already seen that sometimes the temperature affects the properties of materials, but now I want to look at why.

[Boys get up.] So we're going to play a little game called 'What's a solid, what's a liquid?' and we have a couple of volunteers already. Down you come, boys.

[Two boys stand on either side of Tony at the table.] OK, one of you either side, please.
So if you just stand here.
OK, I'll get the things out and I want you tell me whether it's a solid or whether it's a liquid. OK?

Pick it up. [Boy holds up block of wood.] [It's a solid].... Why don't you just give it a knock? [That's a solid].
Give it a bash then.
Oh yeah, right let's have it on the solids side, OK.
[Boy holds liquid in glass.] What about this? [Liquid].

Right, let's give it a swirl round, try not to spill it, right.

[Boy holds up metal bar.] And [solid] give it a knock.
Oh yeah, that sounds like a solid, doesn't it?
Let's erm, let's arrange them this way.
That's good.

[Boy shakes oil bottle.] And this one. [Liquid].
Go on, you can give it a, oh yeah, that's a liquid. Right.
Formally we define a liquid as something that flows to take the shape of the vessel that contains it and solids, solids are - solid.

They don't change shape, right.
What about this stuff? [Solid].
It's a solid, is it?

So when I pull it - it changes shape, so it's a liquid.
But do liquids snap? [No].
But that one did, so where are we going to put this on our table? [It's a solid, because it doesn't confirm to the vessel it's in].
It does, if you wait a long time, let me show you. [Laughter.] Ay, I'm glad you said that.
So this is one, this has conformed to the vessel it's in, hasn't it? So much so that it won't come out! [You can't get it out!]. No.

Do you think it'll bounce? [Probably].
Very good!
Well thank you two, no, not thank you two very much, I have one more, now you're good on the answers, aren't you - OK. [Laughter.]

And I'm not trying to confuse you on purpose.
So let's have a look at this one. [Tony demonstrates properties of 'elastic liquid'.]
In fact, put the top back on. It pongs a bit, this one.

Nothing. [Liquid].
You? [Liquid].
So out we come, liquid, liquid, liquid, liquid.... ... ... liquid, liquid, solid again. [Laughter.]

But, Annie, can you just help me for a moment.
Right, if you just move to this side, so you're between me and Annie and I'm going to reach across you and we're going to make it behave like a solid, so it's pouring.
We cut it and it snaps back into the jar, right.
Now it's behaving like a solid.

So, thank you both very much indeed, great answers. [Applause.]

So what do you want in the heels of your trainers?
Do you want a solid or do you want a liquid?
A liquid that goes 'squidge' - you see when I run, a hundred kilos of me lands on each heel, right.
Added to that is the speed, so the impact is three hundred kilos per heel.

Should I use a big air bag to absorb that energy? [Yes]. Yeah.

But I shouldn't use an air bag on its own, for reasons that I'll show you now.

[Tony stands by table/demonstrates bouncing ball bearing.] You see, you don't want something that's too elastic.
So here's a ball bearing and I'm going to bounce the ball bearing in the tube and it almost jumped out again, it comes all the way to the top and it takes loads and loads and loads of bounces for all the energy from dropping it to be taken away, right.

So if you were running in something like that, it would be like running in a pogo stick, right.
What you want is something that does this, that absorbs the energy quickly.
But we don't want to make trainers out of iron and steel, do we?

You don't want to run in springs that are like pogo sticks, because metal trainers would mean trashed feet, so what we need to do is we need to design better materials to do what's called 'damping' - that's absorbing the energy of the impact.And I need four volunteers from over here. Right, I want you to stand in a line along here.

[Four volunteers stand in line.] And what's your name? [Sian].
Pleased to meet you Sian.
[Tom]. Tom.
[David]. David.
[Rachel]. Rachel, great.
Now you told me you could catch, so there's yours, right, there's yours.
This is for Sian. There's yours, ooh ... good catch. There's yours.

Right, what we want you to do, is Sian, first, hold your hand out, right, let the ball bounce on a solid part of the floor, right, and then catch it on the way back.

Right and leave, and then do it again, but leave your hand where you caught it, so we can see how high it bounced up. Great, there, fine.

Right, and you.
Woops, try again, right. [Laughter.]

I'll tell you what, your hand got to about there, OK and you - oops, right, OK, your hand got to about there.

[Rachel has non-bouncing ball bearing.] And yours? Oh. [Laughter.] That's a shame. We won't make you bend down, we'll just leave it there, right.
You see these different materials are different rubbers.

The molecules that have different amounts of that dancing energy we talked about earlier.
And we make the molecules from special chemical structures, so that they have the properties we want, so let's see if I can catch.
Sian first. Whoa, and you.
Whoa, I missed one.
And you. And again.
Whoa, great, thank you very much indeed.

[Tony holds up chain.] You see the balls were different colours just to give you a clue that they were going to be different, but we can actually put those colours together in one molecule.
So over here is something we call a block copolymer. Wow, big words, those.
Block, meaning that you have a block of one colour, a block of another colour and then that colour again.

So the purple and the blue chains are designed so that they act together to give the optimum damping. And it turns out that that block copolymer is here, this part here, in these fancy trainers.

[Tony holds up trainer.] So would you want to run in shoes that had solid rubber soles? I don't think you would, because the shoes would be far too heavy.
You see, to get the amount of cushioning from a solid, you'd have to run in something that was like a pair of boots made from concrete. This stuff, these trainers have solid or nearly solid rubber soles.

Now, the guy who ran the marathon in these must have had trashed feet. I wouldn't run a marathon in them.
Just look at this. This is what you need in the trainers. [Shot of foam on the overhead screen.] You need foam, not solid.
And Annie's going to come out and help me make some foam. [Annie mixes chemicals.] So we need to mix some chemicals together.

So these are the two chemicals.

And I'm going to give them a good old mix, right.
How are we doing, are they mixing up now? [Just about, yeah].

So imagine this was your trainers. They're in a mould, only the uppers and the polyurethane gets squirted in and what happens is it flows and it flows around the upper and around all the other bits that have been inserted in the shoe. And it keeps on rising and it keeps on rising, yeah, because these trainers are from the land of the rising foam, right?! [Laughter.]

And it gets all the way to the top - and it's not quite gone solid yet, has it.
And it's making little strings and now it's gone solid.

You see the internal structure is the foam.
Yeah, look at this, you can see all the bubbles.
[Tony holds up tangled chain.] When you deform the polymer, which is once again, one of our favourite block copolymers, right, it's got purple bits and blue bits that organise themselves and get separated, so now we have two variables for the sole material. We have the natural damping inside the polymer and how much air is inside the foam and that structure dissipates energy very, very effectively.

Now the shock absorbing properties of polymers doesn't just stop at training shoes.
It can be used to help protect us against one of the planet's most violent and catastrophic natural events.

[Simulation of earthquake in lecture theatre.]

What's happening?
[Tony looks up at overhead screen with video tape of earthquake. Table is wheeled on for demo.] You see, earthquakes really do cause an awful lot of damage and we can use the energy damping properties of polymer molecules to help protect us.
So the buildings - places like the UK, where there are no earthquakes, have metal foundations.
So when they get sprung, right, they just, there's a lot of shaking, then they shake.

But out in areas that are prone to earthquakes, the foundations are made from a special material that's a sandwich and it's a sandwich of a thin layer of rubber in between the pieces of metal and they're all stacked up in the bottom of the building, just like a giant licorice allsort.

And what happens is, when the earthquake comes along, they don't give any energy to the building, they just absorb it all.
Now we can't show you that with a real building, because this building's rather precious, right, so Bipin's going to build a building now, for us.

And like most things he does it's come in ahead of time and under budget, we're really pleased about that! [Laughter.]

OK and now for the earthquake.

[Earthquake demo/model building falls down.]

And the building falls down.
OK, now we're going to make a sandwich.
Because of the loads and the rates are a bit different, we can't make a thin sandwich, so we have to make a slightly thicker sandwich.
He's going to build his building again and on goes the roof, on comes the earthquake.

Hey presto, the building stays standing.
Thank you very much, Bipin. [Applause.]

So far we've looked at the sole and the heel of the trainer and explored the world of grip and elasticity, helping us to protect our bodies and our buildings, but the fantastic properties that these rubbery polymers possess would be useless if we didn't have the ability to stick them together.

How long would your trainers last if they weren't joined up?
And in the next part, we're going to look at the vital ingredient that holds everything together - and that's the glue. [Applause.]

Professor Tony Ryan
So whether you're using trainers or a jumbo jet, the one thing you can't do without when you travel is glue.
So now we're going to enter the sticky world of adhesion.

First of all, what is glue? What sticks and what doesn't and why are some things stickier than others?

You see there are lots of natural adhesives, like the things keeping these [underwater footage/sea creatures cling to rocks] ... clinging to the rocks as the waves rush past.

And if you've got a cold like me, you'll know about this. [Blows nose.]

Natural adhesive, right! [Laughter.]

Now not all glues are the same.
In fact we need to work out what the properties of the glue are before we can use it.
For example, here we need to know what the peel strength will be.
And this is an example of something that will stick, peel off, stick again. [Tony peels off a 'Post-It' note.]

It turns out that this was an adhesive that failed, right.
It didn't do what it was meant to do, but someone was clever enough to work out that it would be very useful indeed.

So, let's go over and have a look at how you measure how sticky things are.
So Ian here's going to run this instrument called an Instron for me and we have some notes some post it notes mounted up and when we start the test, first it takes up the strain in the paper and then the force starts to build as we start to pull it off and then it drops down and there's a little blip at the end as the paper disconnects from the pad, so we can measure the forces involved in pulling these off. Thank you very much, Ian.

Now all of these glues work by dissipating energy.
When you tear them apart, the force is used to deform all the molecules, so here is a glue that's on its way to being useful. [Shot of liquid in a jar.]

At the moment it's still a liquid. And I'll show you.

So there's the 'goopy' liquid flowing down. Now Annie made these and she's mixed the chemicals together that are similar to the ones we use to make the polyurethane foam.
But there's no, well there's not many bubbles in here and at the end of the reaction it's hard, right, and actually rather dry, so it's not like that liquid at all, but in the middle ... it's so sticky I can hardly get the top off, and look at this stuff.

[Shot of glue at 'gel point'.] This glue is the business, right. And this is just at what we call the gel point.
And what the gel point is, is where the molecules have grown to such an extent that they're reaching from one side of the pot to the other.

So when you pull on one bit of a molecule, you're pulling on all the rest.
So now, I need some volunteers to help me play with the gel point.

[Three volunteers stand with Tony.] Now we have some toys and these toys have got the same material - this is for you - they've got the same sticky gel on the end.
Hold it that way, because you need to not touch those bits.

Over you come, please.I want you to all of you to place them in a line.
Let room for everyone and when I say 'go' - yeah, I want you to let go. Go. Right. See that one didn't even stick at all and this one's supercharged and that one's kind of slow, right.

Now, yeah, no you're, you're doing well, you've won the race, mate, this one never got started and this one, it's sticking and then de-sticking and as it rolls round, it gets pressure.

So anyway, thanks a lot, the gigglers can go back. Thank you very much indeed. [Applause.]

You see we fixed that race. [Tony demonstrates results of experiment.] The one that dropped off which is on the floor here is covered in little hairs, because it's been sat in someone's pocket, that didn't stick any more. And the one that won was supercharged by giving it more weight, so it peeled off quicker.

And then the one that came in last, that one worked in the way that they were intended to work, by the balls sticking and then the force of gravity slowly detaching them.

But this stickiness, whilst it's clever, really lags behind nature. You see as usual, nature cracked the adhesion problem long before we did. Barnacles are neat, but these things are the business, right.

[Tony holds up glass container with gecko.] This little beauty, this is a gecko. Can we see him? Yeah, nice. And this gecko has very special feet.

[Container is rotated to show gecko's feet.] He's got half a million bristles per foot and as I slowly turn him upside down, look at those feet. On each foot there's half a million hairs. And on each hair there are these tiny things called spatula and those spatula look like the bottom of a toothbrush, so each hair splits up into lots more hairs, thousands of hairs, just like the end of a toothbrush, but they're so small that there's a billion attachment points on the bottom of each gecko.

A billion hairs, that's unbelievable and they make molecular contact. Those little hairs search out every nook and cranny in the surface and they make an incredibly strong bond, because the contact area is much, much bigger than the gecko's foot.

You see, you can get a strong bond if you have a large contact area, but glueing things together isn't quite that simple. Just put him down there.

[Tony demonstrates that plaster won't adhere to wet skin.] So, I'm going to glue something together now, I'm going to put this plaster on my hand, but my hand's wet and the plaster won't stick. Why is that?

You see I've messed with the molecules. The sticky molecules can't get to my hand. That's why it always says, keep things, keep, make sure the surfaces are clean and dry, on the box, for the adhesive and the way the glue covers the surface depends on the surface tension.

So we went to a school in Sheffield to show what surface tension means.

[Overhead footage of school children act out weak/strong adhesion.] So look these two school kids' surfaces, they're from St. Wilfred's School are not well wetted. There's not good adhesion. So when the red force tries to pull them apart, right, they slip apart rather easy. There's only a couple of rather weak bonds. Whereas if we get the two materials to penetrate each other, so that they're well wetted, then when the red forces try and pull them apart, they can't, because they're really, really stuck.

Now the surface tension is a property of a liquid and a solid. So I'll just test that it mists.

[Shot showing card with various surfaces.] So here I've got glass, copper, polythene and carbon surfaces and I'm going to mist them and you can see that the water drops that have formed have a very different shape.

In fact we can use this surface tension effect to do something rather special. So these gold wafers, these have been prepared up in Sheffield and we've printed a surface on them, where the surface tension's different. So when I breathe on them [sound of breathing] it develops the logo of the Ri perfectly. And that's because the water droplets are slightly different sizes.

[Shot showing evaporation.] And as the water evaporates, the pattern slowly disappears. OK.

Professor Tony Ryan
[Table is wheeled in.] That's not the only thing we can do with surface tension. It controls the interaction of the material and its liquid, and Jon's coming in now, we hope. So he's got a slide and it's on an angle and the bottom of the slide hates water and the top of the slide loves water.

You've just got to find the sweet spot, it's a bit like a tennis racquet. [Shot of water droplets.] See the water droplets running uphill.

Isn't that brilliant, OK. Now the top of the drop is happier in contact with the surface than the bottom of the drop, so everything just 'udges' up so you can actually make the water roll uphill.

It rolls so far that the gravity balances the surface energy. Cheers, mate. Round of applause for Jon. [Applause.]

[Footage on overhead screen of fly and water boatman.] Now, whilst we're very clever in the chemistry department in Sheffield, nature got there first. So up on the screen is a fly that's fallen in the water and swimming towards it is a very hungry pond skater and it's swimming on its elbows, because its elbows are really greasy and the water doesn't like them and the surface tension keeps them up and eventually they all swarm round the fly and get their dinner.

[Table is wheeled on.] Now talking about dinner, or should I say, breakfast, yeah. This that Annie's just brought on is a non-stick pan and here is a Teflon egg, right. [Laughter.]

[Tony demonstrates sticking qualities of Teflon egg onto non-stick pan.] It came as a big surprise to the production team, Teflon's actually white, right. Non-stick pans are coloured just so that you don't get an unsightly looking pan when it kind of picks up the odd scratch. So let's see how non stick that pan is, give it a shake, OK.

So it's a non-stick pan and a non-stick pan surface.

Let's just see if we can stick them on. Now if you have something in a sticky pan it doesn't stick straightaway, does it. So it takes a while if you're cooking something for it to stick, so I want you to count to ten with me.Go - 1-2-3-4-5-6-7-8-9-10.

And it's stuck.
How hard has it stuck?
Well ...Oh, I've only just got it off.
You see we've learned already to stick Teflon things together.
Non-stick frying pans can be made to stick to non stick frying pans, if you know how to manage the surface chemistry.

See I've followed those rules. I've made something and put it in here. Even if it was ... we glued two pieces of aluminium together, so we first roughened the surfaces by shooting sand at them and then we cleaned them of any grease by washing them with a solvent and we chose a glue that was well matched to the surface and it covered every nook and cranny and to test how is it, how good it is, I'm going to use a friend of my family, a lad called Ollie. You can come down now Ollie.

[Ollie stands with Tony.] Oh, sorry, oh, you're behind me, you've moved. How are you doing mate? [All right].You all right? [Yeah].
OK, so what we're going to do is me and you are going to get in this chair - [laughter] - right.
[Chair is lowered from ceiling.] Down it comes. You don't have to worry though, alright?

So this, do you trust it? [Yeah].
Are you sure? Do you think it's as good a bond as that egg was to that frying pan? [Yeah].

Oh, OK. See, there's the glued part ... let's get in here. [They sit on chair.] Don't be frightened, Ollie, we're not going far, OK. [Laughter]

Up we go, up we go, Ollie, we're going up.
Ho ho, glued together, how are we doing?

This bond, which isn't very big will hold up to four tons, it could have picked up a double decker bus.
See the glues we use for all these jobs of putting these aluminium pieces together are the same ones that are used to glue jumbo jets and land speed record holders.
So today we've explored the science and the materials that'll help us become the next Paula Radcliffe or Johnny Wilkinson. Even if it's just in the playground.

[Ollie and Tony sit on chair.] And I hope you realise, give us a smile mate, I hope you realise it's not just about your trainers, it's about every time you move, by train, plane or automobile.

[Applause/music/credits roll.]