Translator: Takuma Suzuki Reviewer: Hiroko Kawano
Have you watched the movie "Fantastic Voyage"?
Thank you very much.
If you have, you must be quite old.
(Laughter)
Well, I watched it a long time ago.
The story is about saving a scientist who has a blood clot in his brain.
A medical team of five people
are called up and somehow get on a submersible vessel.
And these people are shrunk by cutting-edge science technology
to venture into the vein of the scientist.
Though they face a variety of troubles on their way, of course,
they work together to demolish the clot and finally, save the scientist.
Of course, this story is science fiction.
But will such a world come someday?
In fact, in our daily life, there are a number of technologies
that were described in SF worlds and turned into reality later,
including your cell phones, tablet PCs as well as drones,
which were totally dream technologies until a couple of decades ago.
One psychologist says,
"Fiction, like SF, gives us opportunities for thought experiments."
A thought experiment takes place inside your head, costing you nothing.
And I'm also one of those scientists
who has long dreamed of such miniature worlds in our minds.
What reminded me of this miniature world again
was "The Singularity Is Near,"
which is a non-fiction book released in 2005 by futurist Ray Kurzweil.
One passage in the book says,
"By 2020, we will be developing robots
the size of a human red blood cell or even smaller."
This reminded me of that film, "Fantastic Voyage."
It has been 50 years since the release of the film,
and I'd like to talk about how far the robots have been developed as of today
along with my research.
First of all, what is a robot?
If you take a closer look,
you will find that a robot has three essential elements:
first, there's a sensor that senses the surrounding environment,
the second is a processor that processes the information,
and the third is a motor that receives instructions from the processor
and converts it into motion.
In other words, we can understand
that a robot is a system that has all these three elements.
However, the robots in that movie or book are incredibly small.
How small?
Compared to the robots around you,
it's slightly bigger than a red blood cell
and a little smaller than the diameter of our hair.
We can't possibly create such small robots using traditional methodologies.
Then, how can we do it?
Of the three elements I mentioned,
we realized the key was the motor.
But how can we find a technology to make such a tiny motor?
When I was a student, I learned a little bit of biotechnology,
and I decided to conduct my research based on it.
I looked particularly at molecular machines which consist of proteins
and that are involved in the transport of various substances in our body.
The molecular machine can obtain energy by breaking down ATP,
a chemical compound which is abundant in our body.
So, if we use this molecular machine
as the engine of our molecular robot,
we'll no longer have to worry about the energy for in-vitro tasks,
and that was our conceptual starting point.
By the way, the submersible was powered by nuclear energy.
I suppose it is okay if it is small?
(Laughter)
Soon I started to develop this motor with my lab students.
However, we faced a series of problems.
Because -
I said I was familiar with biotechnology,
which, in fact, was an exaggeration.
(Laughter)
My knowledge only stayed inside the classroom,
and I shouldn't really say this in front of my students,
but it was mostly focused on "sleep-learning."
(Laughter)
Well, as I couldn't show off my ignorance,
I furtively read papers and books, learning through trial and error,
and finally, I got to be able to move the molecular machine in the lab.
This movie shows how the motor moves in the water.
What do you think?
This is the best healing video for me.
(Laughter)
The size of the motor is roughly 10 micrometers,
which corresponds to the diameter of red blood cells.
In this way, I was able to get a motor for our robot,
though I still had no idea about the other two required elements:
processor and sensor.
As for the processor development, I met a key person at a lecture.
Dr. Kuzuya had just come back from the US, where he studied DNA nanotechnology.
Listening to his lecture,
I instinctively discovered the candidate for the processor:
our body's DNA.
DNA is involved
in transmitting and storing genetic information in our body.
DNA also has an important recognition function
based on the four codes: A, T, G and C.
Back in those days, by utilizing this recognition function,
the "molecular computer" was developed
in order to store digital data and even to solve mathematical problems.
We immediately started this collaborative research back in Sapporo,
which was not that easy, though.
This was because,
when you put the DNA on the motor,
it would suddenly stop moving.
We have struggled with this problem for a year,
but the situation did not improve.
This movie shows the best combination of the motor and the DNA,
but it's only wiggling around.
And then, we gained momentum again.
A research group was established to focus more on the molecular robot,
and Prof. Kuzuya and I were selected to join the group.
We couldn't repeat the same mistake, however,
so what could we do?
In the field of molecular computing,
it was common to proactively use very long and complex DNA sequences.
And we were also planning to use such DNA.
But we gave up on that idea
and decided to use a short sequence of DNA by decreasing the number of bases.
And instead of using a complicated sequence,
we decided to use sequences with simple repetitions of three bases.
This change of idea worked well.
At last, the motor that was equipped with the DNA started to move smoothly.
At that time, I was extremely excited,
so I even colored the motors in red and green.
(Laughter)
However, what kind of programs should we write in these molecules?
We still had a way to go.
These are molecules.
I thought only one molecule might be too weak to work.
Even in the movie,
they were able to complete their task by working together.
This kind of collaborative work is a common phenomenon in nature.
For instance, birds can fly to incredibly far wintering places by forming a flock,
and fish can deceive the enemy by changing the form of their swarm.
Likewise, ants can form a herd
to carry a huge object that one ant cannot possibly carry.
Obviously, some of them are being carried.
(Laughter)
In this way, a flock enables them to accomplish their tasks
that could not otherwise be done.
So, we decided to input the program
that supports the formation and the dissociation of the swarm
within the molecular system.
This is the idea I had been working on for many years
in collaboration with Prof. Hess from Columbia University, New York,
where I studied in the past.
First, the information which is made from DNA
is passed to the molecular system.
Then, the motors will recognize the information and start to snuggle up.
However, since we had simplified our processor so far,
I was still not sure if the DNA sequence could work properly or not.
So first, we carefully colored the two types of filaments
and tried to deploy them into one place.
Here I couldn't see any of the filaments interfering with each other.
Then tentatively,
by using a device called a pipetter, I applied a drop of DNA
that contains an instruction "to swarm" the filaments.
This picture shows how we perform our experiments with a pipetter.
FYI, this is the microscope we use for experiments.
Let's see what happens:
the filaments I mentioned before soon started to gather together
and eventually formed a huge swarm.
(Applause)
Thank you.
Because of the blending of the red and green filaments,
which had been colored previously,
the swarms became yellow.
Now, when we applied another drop of DNA
containing an instruction to direct the swarm to dissociate,
the swarm immediately started to dissociate.
This movie was taken right after the application of DNA.
Let's zoom in,
and you'll see it's dissociating,
and the red and green filaments are coming out from the yellow swarm.
Interestingly, we found out the morphology of the swarm could be changed
by slightly tuning the structure of the motors.
Here, the swarm is swirling and rotating, just like a school of fish.
(Applause)
Thank you.
For sure, when a drop of DNA is again applied,
nearly 300 filaments come out of the swarm.
Slightly spooky, isn't it?
(Laughter)
The recent study shows
that multiple commands can be applied to this swarm simultaneously.
For example, first, we made a command
to form yellow-colored swarms and rotate in the spot,
and secondly, to make green-colored swarms and wander around.
See what will happen.
Don't you think they are following the given instructions?
(Laughter)
As you can see from the movie,
some green swarms are still joining the yellow swarms.
They are kind of searching the others and go searching around.
In this way,
our molecule robot project literally started running.
Yet there was one missing part,
which was a sensor.
Luckily, in a research seminar,
I met Prof. Asanuma, who was developing a sensor.
He said when a particular compound is inserted into the DNA strand,
it can be used as a light switch.
For example,
when the yellow light is applied, the processor will be turned on;
and when purple light is applied, the processor will be turned off.
Let's see what happens:
when the yellow light is applied, the red and green colored filaments
gather together and form an amoeba-like swarm.
And then, the purple light - like this sort of color -
is applied to it, the swarm starts to dissociate.
Our recent research proved that the sensor's response to the light
does not depend on the form of the swarm.
This rotating swarm also starts to dissociate
when the light is applied.
It is right to say
that this sensor is equivalent to the eye of our molecular robot.
In this way, we made the robot with a motor, a processor and a sensor,
which we may call a prototype of molecular robot.
But what can it do?
I would like to conclude my presentation
by introducing a simple demonstration.
In this movie, we use a crystal to resemble a sugar cube,
and we throw it into the swarm of a molecular robot.
Then we see that the crystal is captured and transported by the swarm.
(Applause)
I want to tell you that we couldn't make it happen with only one filament;
this feat was possible only by creating and utilizing a swarm.
What our molecular robot is capable of doing is still limited,
but imagine if more molecular robots with various functions and structures
are developed in the future and work together as swarms;
I believe they'll have unlimited possibilities for applications.
Likewise, what I can do is quite limited.
Today, I talked about our molecular robots,
which wouldn't have been possible
without the cooperation of many scientists.
It may be a long way off, but someday in the future,
I'd like to work together with all
to make happen what was shown in the movie.
And our dream is to solve problems,
even if it's a little bit,
that we as human beings will face.
I believe if we work together, the possibilities are infinite.
Thank you for your attention.
(Applause)