Transcriber: Lisa Rodriguez Reviewer: Rhonda Jacobs
Today, I'm going to talk about water.
Water is so familiar to us.
I have a question to you:
How many different types of water do you know?
(Audience - silent) Three.
Yes, three.
Liquid, ice and the vapor.
However, these three types of water
cannot explain how water climbs up
to the top of a giant tree against the gravity force.
We know water is so fragile,
it would be broken as soon as you pull it out.
As another example,
we cannot explain
how this small snow flea can survive
at extremely low temperatures in Arctic area.
We know water gets frozen
immediately below freezing temperature.
More importantly, water is so close to us.
As you know, water takes about 70 percent of our body.
However, we do not know why we need that much water for our life.
That's the reason why scientists say
that water is the most studied but the least understood.
Today,
I'm going to introduce
a new type of water.
So we named chain-like water. It looks like this.
[Chain-like Water; 0.3 nm]
It has been there, but we just found it.
Today, I would like to share how we discovered chain-like water
and why the findings are so cool to us.
130 years ago,
the mysterious behavior of water was recognized by scientists.
They proposed a very hypothetical model called the mixture model.
The mixture model has been evolved with time.
As you can see here, according to mixture model,
water is very, very small scale.
Water is made of two components:
one is clusters, the other is liquid water.
However, this model has been highly debated
because of lack of experimental evidence.
When I joined Boise State University in 2004,
I was so interested in proving the mixture model experimentally.
However, it was very challenging to us
because of its size and the mobile nature of water.
Instead, we started to build a tool that can measure a delicate force
generated by water confined between a sharp probe and a flat surface.
This tool also can stretch and compress
those tiny waters, using a computerized actuator.
If you zoom in that tip area by 10 million times,
you will see this kind of structure.
When you bring tip very close to the surface,
at certain distance, the surrounding vapor
condensed between the tip and surface
through a process called condensation.
Amazingly, my tool can actually tell us
if the trapped water is liquid water or clusters.
Let's see how that is possible.
This slide shows how the pulling force would be
with distance when trapped water is liquid water.
When distance is small,
you can expect a pretty thick bridge and the force is large.
When the distance becomes greater,
now the bridge gets thinner and the force is smaller.
This graphs shows just like kind of a slash pattern.
Now, so what if the trapped water is chain-like water like this?
Then, when this is in the collapsed state,
just like this, it easy to pull out, therefore the force is small.
However, once it's stretched out, it's hard to stretch out.
So this idea also can be represented by using a graph.
So this graph clearly shows, it looks like kind of a tilted J pattern.
This is the way how my tool
can report what type of water we see.
If you see slash pattern, that means that we see liquid water.
If you see J pattern, that means that you see chain-like water.
Then the question is, what difference does the distance make for your water?
We can only find the answer through experiment.
Let's do experiment.
Can you see J pattern and the slash pattern?
In these two boxes, so you can see two J patterns.
That clearly shows the existence of chain-like water.
When I saw this data for the first time, I was almost in shock.
It was one of the most exciting moments in my research career.
In this slide, you can see a bundle of chains
are aligned vertically between the probe and the surface.
Let's go back to our original question.
Does cluster water exist at the nanoscale?
The answer is Yes, but it exists as chain-like water.
After furthering our investigation
[we say] that the water is amazingly strong,
even stronger than concrete.
Now, let's go back to our original data.
Do you see liquid water?
Yes, we see two slash patterns.
But in this slide, as you can see,
the structures are really different from what we learned from slash patterns.
This is because
the middle chain water is so stiff,
only two bridges below tip and above sample surface
is responsible against the distance variations.
This is the reason why we have slash patterns for these structures.
Let's go back to our original question about the mixture model.
Does liquid water exist at the nanoscale?
Yes, but liquid water exists together with chain-like water.
Therefore, we proved the mixture model idea experimentally.
So now, this is water.
If you zoom in this water 10 million times,
you will probably see that kind of structure.
But this structure is amazing because they are very complementary.
Liquid water is fast;
chain-like water is slow.
Liquid water likes hydrophilisty,
whereas chain-like water likes hydrophobicity.
And liquid water is fragile;
chain-like water is strong.
But this water is also very cooperative.
After investigation, we found that these waters are really cooperative.
As you can see here, the V shape
is the abrupt transition from liquid water to chain-like water.
This idea can be illustrated as follows.
If you make a small variation in distance,
suddenly the liquid water evaporates, leaving the chain-like water only.
So this result suggests that
both waters are very cooperative with each other.
Now, how does nature adapt
this amazing structure and the property of water?
So now we know, right, that the water climbs up the tree
in the form of chain-like water.
According to physics theory,
the size of a liquid shouldn't exceed a critical size
to form the ice crystals.
As you can see here, the chain-like water is in the way between two liquids,
preventing their association,
and thus preventing them from forming ice crystals.
Nature also uses
the abrupt V-shape transition
to control the ions in our cells,
such as nerve cells.
So as you can see in this slide,
the ions can freely move from one place to another place,
in the open state that we saw previously.
And then now,
if a molecular machine called a protein
decreases the distance slightly, whatever would be,
that channel is gone, resulting in the closure state.
That's the way how the ion is controlled in our body.
So the answer to the question,
why we need so much water in our body, is not easy.
However, the ion channel idea gives us a clue,
the water is very active and also very cooperative,
not just kind of background material or just a kind of spectator.
So water is a very important component in our body.
So that indicated that water is very, very important in our health.
I believe that the finding
of this chain-like water would be huge
because we can understand better about molecular function
by understanding how water is involved in those processes.
So we just discovered the water, and then now,
so let's see what will happen in the future.
Finally, I have a question to you.
How many different types of water do you know now?
(Laughter)
Thank you.
(Applause)