The fascinating science of bubbles, from soap to champagne

In this whimsical talk and live demo, scientist Li Wei Tan shares the secrets of bubbles -- from their relentless pursuit of geometric perfection to their applications in medicine and shipping, where designers are creating more efficient vessels by mimicking the bubbles created by swimming penguins. Learn more about these mathematical marvels and tap into the magic hidden in the everyday world.

Some years ago, I was visiting Paris

and walking along the Seine River
during a beautiful summer afternoon.

I saw giant bubbles
floating on the riverbank,

like this one.

The next moment, it popped and was gone.

Making them were two street performers
surrounded by a crowd.

They visibly make a living
by asking for donations

and by selling pairs of sticks
tied with two strings.

When I was there, a man bought
a pair of sticks for 10 euros,

which surprised me.

I am a scientist who is
passionate about bubbles.

I know the right trick
to make the giant bubbles

is the right soapy water mixture itself --

not the sticks,

which may be needed,

but you can easily make them at home.

Focusing on the sticks makes us not see
that the real tool is the bubble itself.

Bubbles might seem like something
just children make while playing,

but sometimes it can be really stunning.

However, there are more
fascinating science to bubbles,

such as problem-solving tools.

So I would like to share with you

a few stories about
the science of creating bubbles

and the science of eliminating
the microscopic ones.

Since it's up on the screen,
let's start with the soap bubble.

It is made from very common substances:

air, water, soap, in the right mixture.

You can see soap bubbles
constantly changing their colors.

This is due to the interaction with light
at various directions

and the changes of their thickness.

One of the common substances,
water molecules,

are formed by two atoms of hydrogen
and one atom of oxygen -- H2O.

On most surfaces, water droplets
tend to curve inwards,

forming a semihemisphere shape.

This is because the water droplet's
surface is like an elastic sheet.

The water molecule on the surface
is constantly being pulled inwards

by the molecule at the center.

And the quality of the elasticity
is what we call "surface tension."

Now by adding soap,

what happens is the soap molecule
reduces the surface tension of water,

making it more elastic
and easier to form bubbles.

You can think of a bubble
as a mathematical problem-solver.

You see it relentlessly trying
to achieve geometry perfection.

For instance, a sphere is the shape
with the least surface area

for a given volume.

That's why a single bubble
is always in the shape of a sphere.

Let me show you. Check it out.

This is a single bubble.

When two bubbles touch each other,

they can save materials
by sharing a common wall.

When more and more bubbles
are added together,

their geometry changes.

These four bubbles are added together.

They meet at one point at the center.

When six bubbles are added together,

a magical cube appears at the center.

(Applause)

That is surface tension at work,

trying to find the most effective
geometry arrangement.

Now, let me give you another example.

This is a very simple prop.

This is made from two layers of plastic

with four pins connected to each other.

Imagine these four pins represent
four cities that are equally apart,

and we would like to make roads
to connect these four cities.

My question is: What is the shortest
length to connect these four cities?

Let's find out the answer
by dipping it into the soapy water.

Remember, the soap bubble forms
will always try to minimize

their surface area

with a perfect geometry arrangement.

So the solution might not be
something you expected.

The shortest length
to connect these four cities

is 2.73 times the distance
between these two cities.

(Applause)

Now you've got the idea.

The soap bubble forms will always try
to minimize their surface area

with a perfect geometry arrangement.

Now, let us look at bubbles
in another perspective.

My daughter, Zoe, loves visiting zoos.

Her favorite spot is Penguin Cove
at Marwell Zoo in Southern England,

where she could see penguins
swim at speed under the water.

One day, she noticed
that the body of penguins

leaves a trail of bubbles when they swim

and asked why.

Animals and birds like penguins

that spend a lot of their time
under the water

have evolved an ingenious way
of utilizing the capability of bubbles

to reduce the density of water.

Emperor penguins are thought to be able
to dive a few hundred meters

below the sea surface.

They are thought to store
the air under their feathers

before they dive

and then progressively release it
as a cloud of bubbles.

This reduces the density
of water surrounding them,

making it easier to swim through

and speed up their swimming speed
at least 40 percent.

This feature has been noticed
by the ship manufacturers.

I am talking about the big ships here,

the ones that are used to transport
thousands of containers across the ocean.

Recently, they developed a system
called "air lubricating system,"

inspired by the penguins.

In this system, they produce
a lot of air bubbles

and redistribute them across
the whole of the ship,

like an air carpet
that reduces the water resistance

when a ship is moving.

This feature cuts off the energy
consumption for the ship

up to 15 percent.

Bubbles can also be used for medicines.

It can also play a role in medicines,

for instance, as a method for noninvasive
delivery systems for drugs and genes

to a specific part of the body.

Imagine a microbubble

filled with a mixture
of drugs and magnetic agents

being injected into our bloodstream.

The bubbles will move to the target areas.

But how do they know where to go?

Because we placed a magnet there.

For instance, this part of my hand.

When the microbubbles
move to this part of my hand,

we can pop it via ultrasound

and release the drug
exactly where it's needed.

Now, I mentioned about
the science of creating bubbles.

But sometimes we also need to remove them.

That's actually part of my job.

My exact job title is
"ink formulation scientist."

But I don't work on the ink
that you use for your writing pens.

I'm working on some cool applications

such as organic photovoltaics, OPVs,

and organic light-emitting diodes, OLEDs.

Part of my job is to figure out
how and why we want to remove the bubbles

from the ink that my company produces.

During the formulation-mixing process,

or preparation process,

we mix active ingredients,
solvents and additives

in order to achieve the formulations
with the properties we want

when the ink is being used.

But just like you would make drinks

or bake cakes,

it is unavoidable that some air bubbles
will be trapped inside that ink.

Here, we are talking
about a different space

from the bubbles I'd seen in Paris.

The bubbles that are trapped
inside those inks

vary between a few millimeters,

a few microns

or even a few nanometers in size.

And what we are concerned about

is the oxygen and the moisture
that is trapped inside.

At this size scale,
removing them is not easy.

But it matters,

for instance, for organic
light-emitting diodes inks

that we can use to produce display
for your smartphone, for example.

It's supposed to last for many years,

but if the ink that we use has been
absorbed with oxygen and moisture

[which] are not being removed,

then we can quickly see
dark spots appear in the pixels.

Now, one challenge we face
in removing the microbubbles

is that they are not very cooperative.

They like to sit there,

bathing in the ink without moving much.

But how do we kick them out?

One technology we use

is to force the ink going through
a thin, long and tiny tube

with a porous wall,

and we place the tubes
inside the vacuum chamber,

so that the bubbles can be
squeezed out from the ink

and be removed.

Once we manage to remove the bubbles
from the ink that we produce,

it is time for celebration.

Let's open a bubbling champagne.

Ooh, this is going to be fun!

(Laughter)

Woooo!

(Applause)

You could see a lot of bubbles
rushing out from the champagne bottle.

These are the bubbles
filled with carbon dioxide,

a gas that's been produced during
the fermentation process of the wine.

Let me pour some out.

I can't miss the chance.

I guess it's enough.

(Laughter)

Here, I can see a lot of microbubbles

moving from the bottom of the glass
to the top of the champagne.

Before it pops,

it will jet tiny droplets
of aroma molecules

and intensify the flavor of champagne,

making us enjoy much more
the flavor of champagne.

As a scientist who is
passionate about bubbles,

I love to see them,

I love to play with them,

and I love to study them.

And also, I love to drink them.

Thank you.

(Applause)