How to pronounce "adhesion"

Translator: Hiroko Kawano Reviewer: Tanya Cushman

So I'd like you to join me on a field trip,

and I want to go to the beach and take you all to the beach

and so enjoy the sea air and the salt spray.

And let's go down to the water's edge,

and you'll notice we're getting knocked around by the waves,

and it's really difficult to stay in place, right?

But now, look down,

and what you're going to see

is that the rocks are covered by all sorts of sea creatures

that are just staying there in place, no problem.

It turns out that if you want to survive in this really demanding environment,

your very existence is dependent upon your ability to make glue, actually.

So let me introduce you to some of the heroes of our story,

just a few of them.

So these are mussels,

and you'll notice they're covering the rocks,

and what they've done is made adhesives,

and they're sticking down on the rocks,

and they're sticking to each other, actually.

So they're hunkered down together as a group.

This is a close-up photograph of an oyster reef,

and oysters, they're amazing.

What they do is they cement to each other,

and they build these huge, extensive reef systems.

They can be kilometers long, they can be meters deep,

and arguably, they are the most dominant influence

on how healthy any coastal marine ecosystem is going to be

because what they do is they're filtering the water constantly,

they're holding sand and dirt in place.

Actually, other species live inside of these reefs.

And then, if you think about what happens when a storm comes in,

if the storm surge first has to hit miles of these reefs,

the coast behind it is going to be protected.

So they're really quite influential.

If you've been to any rocky beach pretty much anywhere in the world,

you're probably familiar with what barnacles look like.

And so what these animals do -

and there's many others, these are just three of them -

is they make adhesives,

they stick to each other and to the rocks and they build communities,

and by doing this, there's a lot of survival advantages they get.

So one of them is that just any individual is subjected to less of the turbulence

and all the damaging features that can happen from that environment.

So they're all hunkered down there.

Then, also, there's a safety in numbers thing

because it also helps you keep away the predators,

because if, say, a seagull wants to pick you up and eat you,

it's more difficult for the seagull if they're stuck together.

And then another thing is it also helps with reproductive efficiency.

So you can imagine that when Mr. and Mrs. Barnacle decide,

"OK, it's time to have little baby barnacles" -

I won't tell you how they do that just yet -

but when they decide it's time to do that,

it's a lot easier,

and their reproductive efficiency's higher if they're all living close together.

So we want to understand how they do this:

How do they stick?

And I can't really tell you all the details,

because we're still trying to figure it out,

but let me give you a little flavor

of some of the things that we're trying to do.

This is a picture of one of the aquarium systems we have in our lab,

and everything in the image is part of the system,

and so what we do is we keep -

and you can see in the glass tank there, at the bottom, a bunch of mussels.

We have the water chilled, we have the lights cycled,

we actually have turbulence in the system

because the animals make more adhesives for us

when the water is turbulent.

So we induce them to make the adhesive,

we collect it, we study it.

They're here in Indiana;

as far as they know, they're in Maine in February,

and they seem to be pretty happy, as far as we can tell.

And then we also work with oysters,

and up top, it's a photo of a small reef in South Carolina,

and what we're most interested in is how they attach to each other,

how they connect.

So what you can see in the bottom image is two oysters cementing to each other.

We want to know what's in between,

and so a lot of times, we'll cut them and look down,

and in the next series of images we have here,

you can see, on the bottom, we'll have two shells,

the shell of one animal and the shell of another animal,

and the cement's in between.

If you look at the image on the right,

what you can maybe see

is that there's structure in the shell of each animal,

but then, the cement actually looks different.

And so we're using all sorts of fancy biology and chemistry tools

to understand what's going on in there,

and what we're finding is the structures are different

and the chemistry is actually different, and it's quite interesting.

And in this picture -

I guess, let me step back before I tell you what this is.

So do you know the cartoon "The Magic School Bus"?

Or if you're a little bit older, "Fantastic Voyage," right?

And you remember, they had characters

that they would shrink down to these microscopic levels,

and then they would sort of swirl in

and swim around and fly around all these biological structures?

I think of this as like that, except for it's real in this case.

And so what we did is we have two oysters that are stuck together,

and this area used to be completely filled in with the cement,

and what we're finding is that the cement has lots of different components in there,

but broadly speaking, there are hard, non-sticky parts

and there are soft, sticky parts,

and what we did is we removed the non-sticky parts selectively

to see what's left -

for what's actually attaching the animals -

and what we got is this,

and we can see there's a sticky adhesive that's holding them together.

And I just think it's a really cool image

because you can imagine yourself flying in and going back there.

Anyways, those are some of the things we're doing to understand

how marine biology is making these materials.

And from a fundamental perspective, it's really exciting to learn.

But what do we want to do with this information?

Well, there's a lot of technological applications

if we can harness what the animals are doing.

So let me give you one example.

So imagine you're at home

and you break your favorite figurine or a mug or something like that.

You want to put it back together.

So where do you go?

You go to my favorite place in town,

which is the glue aisle of the hardware store.

I know where you spend your nights

because you're all hip, cool people, because you're here,

and you're going to bars and concerts -

this is where I hang out every night.

So anyways,

so what I want you to do is get one of every adhesive that's on the shelf,

bring it home,

but before you try to put things back together,

I want you to try to do it in a bucket of water.

It's won't work, right? We all know this.

So obviously, marine biology has solved this,

so what we need to do is figure out ways to be able to copy this ourselves.

And one of the issues here

is you can't just go and get the materials from the beach,

because if you get some mussels and try to milk them for their adhesive,

you'll get a little bit of material,

but you're never going to have enough to do anything with, just enough to see.

We need to scale this up, ideally maybe train-car scale.

So on the top is an image of one of the types of molecules

that the animals use to make their glue,

and what they are is very long molecules called proteins,

and these proteins happen to have some fairly unique parts in them

that bring about the adhesive properties.

What we want to do is take those little parts of that chemistry,

and we want to put it into other long molecules that we can get,

but that we can make on a really large scale,

so you might know them as plastics or polymers,

and so we're sort of simplifying what they do

but then putting that adhesion chemistry into these large molecules.

And we've developed many different adhesive systems in doing this.

When you make a new adhesive that looks pretty good, what do you do?

You start running around the lab, just sticking stuff together.

In this case, we took a bit of a glue and glued together two pieces of metal.

We hung something from it to see what it looked like,

so we used a pot of live mussels, and we thought we were very clever.

(Laughs)

We're obviously much more quantitative about this most often,

and so we benchmark against commercial adhesives,

and we actually have some materials now that are stronger than superglue.

So to me, that's really cool.

That's a good day in the lab: it's stronger than superglue.

And here's something else that we can do.

So this is a tank of seawater,

and then in that syringe is one of our adhesive formulations.

What we're doing is we're dispensing it completely underwater

on a piece of metal.

And then we want to make an adhesive bond, or joint.

So we take another piece of metal,

and we put it on there and just position it.

And you want to let it set up for a while, give it a chance,

so we'll just put a weight on it, nothing fancy.

This is a tube with lead shot in it, nothing fancy.

And then you let it sit for a while.

So this has never seen air; it's completely underwater.

And you pick it up.

I never know what's going to happen; I'm always very anxious here.

You pick it up ...

and it stuck.

To me, this is really cool.

So we can actually get very strong underwater adhesion.

Possibly, it's the strongest or one of the strongest underwater adhesives

that's ever been seen.

It's even stronger than the materials that the animals produce,

so for us, it's pretty exciting, it's pretty cool.

So what do we want to do with these things?

Well, here are some products that you're probably really familiar with.

So think about your cell phone, your laptop, plywood in most structures,

the interior of your car, shoes, phone books - things like this.

They're all held together with adhesives,

and there's two main problems

with the adhesives used in these materials.

The first one is that they're toxic.

So the worst offender here is plywood.

Plywood or a lot of furniture or wood laminate in floors -

a main component of the adhesives here is formaldehyde,

and it's maybe a compound you've heard of.

It's a gas, and it's also a carcinogen,

and so we're constructing a lot of structures from these adhesives,

and we're also breathing a lot of this carcinogen.

So not good, obviously, right?

The other issue is that these adhesives are all permanent.

And so what do you do with your shoes or your car or even your laptop

at the end of life, when you're done using it?

For the most part, they end up in landfills.

There's precious materials in there

we'd love to be able to get out and recycle them,

but we can't do it so easily,

because they're all stuck together permanently, right?

So here's one approach we're taking to try and solve some of these problems,

and what we've done here is we've taken another long molecule

that we can actually get from corn,

and then into that molecule,

we've put some of the adhesion chemistry from the mussels.

So because we've got the corn and we've got the mussels,

we call this our surf-and-turf polymer.

And it sticks. It sticks really well.

It's very strong.

It's also bio-based. That's nice.

But maybe more importantly, here, it's also degradable;

we can degrade it under very mild conditions,

just with water.

And so what we can do is we can set things up

and we can bond them strongly when we want,

but we can also take them apart when we want.

It's something we're thinking about.

And here is a place where a lot of us want to be.

Actually, in this specific case, this is a place we do not want to be,

but we'd like to replace this.

So sutures, staples, screws:

this is how we put you back together if you've had some surgery or an injury.

It's just awful. It hurts.

In the case of the sutures,

look at how much you're making concentrated, mechanical stresses

as you pull things together;

you're making sites for infection;

poke holes in healthy tissue - it's not so good.

Or if you need a plate to hold together your bones,

look at how much healthy bone you have to drill out

just to hold the plate in place - so this is awful.

To me, it looks like these were devised in a medieval torture chamber,

but it's our modern surgical joinery.

So I'd love it if we'd get to a place where we can replace systems like this

with adhesives, right?

It's not easy.

We're working on this, but this is not easy.

So think about what you would need for adhesives in these cases.

So first of all,

you would need an adhesive that will set in a wet environment.

And if you look at the silly little picture there,

it's just to illustrate that our bodies are about 60 percent water,

so it's a wet environment.

It's also to illustrate that this is why I am a scientist and not an artist.

I did not miss my calling at all.

So then, the other requirements you need for a good biomedical adhesive:

it needs to bond strongly, of course,

and it needs to not be toxic.

You don't want to hurt the patients.

And getting any two of those requirements in a material is pretty easy.

It's been done many times.

But getting all three hasn't been done; it's very hard.

And then if you talk to surgeons, they get really picky:

"Oh, actually I want the adhesive to set on the same time frame as the surgery."

Oh, okay.

Or, "Oh, I want the adhesive to degrade

so the patient's tissues can remodel the site."

So this is really hard. We're working on it.

This is just one image we have.

So we're getting all sorts of bones and skin and soft tissue and hard tissue,

and sometimes we'll whack it with a hammer.

Usually, we're cutting it in very precise shapes;

then we glue them back together.

We've got some exciting results, some strong materials,

some things that look like they're not toxic.

They set wet, looks pretty good,

but I won't tell you we've solved the wet-adhesion problem,

because we haven't,

but it's certainly in our sights for the future.

So that's one place that we'd like to see things go farther down the road.

There's lots of other places, too, you can imagine,

we might be better off if we could get more adhesives in there.

So one thing is cosmetics.

So if you think about people putting on fake nails or eyelash extensions here -

like this -

what do they use?

They use very toxic adhesives right now.

So it's just ripe for replacement.

That's something we'd like to do.

And there are other places too.

So think about cars and planes.

The lighter you can make them,

the more fuel efficient they're going to be.

And so if we can get away from rivets and from welding

to put more adhesives in there,

then we might be better off

with our future generation of transportation.

So for us, this all comes back to the beach.

So we look around and we wonder, "How do these sea creatures stick?

And what can we do with the technology?"

And I would argue that we have really a lot of things we can still learn

from biology and from nature.

So what I'd like to encourage you all to do in the future

is put down your nonrecyclable laptops and cell phones

and go out and explore the natural world

and then start asking some of your own questions.

Thanks very much.

(Applause)