[Astronaut Don Pettit:] The bio-experiments have captured
some alien virus, and we're culturing it, and it's trying
to climb out of its vat.
Ok, well, here I have these little laptop speakers
that I used last week for oscillating spheres of water,
and this week I'm going to use the same speakers
with some cornstarch solution.
There's my cornstarch solution.
It came in my bonus food containers.
You just pump a little water in there and knead it around,
and now you have some cornstarch solution that's
about as thick as pancake batter.
And cornstarch is a really unique fluid.
It's a non-Newtonian fluid which means
that it doesn't behave like water.
Its viscosity changes with the environment around it,
and we'll see some effects of that
when we put it on the speakers.
And there you go.
If you start slowly it's just about like pancake batter.
You hit it fast, and it effectively turns into a solid
which is one of the neat shear thickening properties.
Now, I'm vibrating the speaker, and this is around 50 to 65 Hz.
I'm sweeping the frequency.
And you get a whole series of really neat lobes
on the free surface,
and at first order this doesn't look much different
than what water does.
But just wait what happens here
when I give this a little disturbance, and you'll see
that it doesn't behave quite like water.
So look at that!
You get these structures trying to climb up
and out of the speaker.
And what you see here is a balance
between surface tension force and the shear force imparted
into the fluid from the speaker oscillating.
And you could do this on Earth, I understand.
So here we don't have to worry about the effects of gravity
because we're on space station,
and the gravity effects have basically been nulled
out by our orbital motion.
Here, we're going to poke it again.
Look at this.
And once you get this perturbation going then you get
these structures growing out.
And the vibration from the speaker is turning the
cornstarch partly into this solid material, and it starts
to move up and out of the speaker well,
but as soon as it gets away from the speaker well, it's insulated
from the shear, and it starts to turn back into a liquid again,
and then surface tension pulls it back into the speaker.
That's my simple explanation for what's going on there.
I also think we might be able to use this
as the zero-gravity equivalent of a lava lamp.
Now, I'm changing the frequencies around,
and then I can vary the amplitude.
These are all played back real time.
These aren't slow-motion or high-speed events.
You're seeing this as how it actually looks.
Now, here we've turned the frequency up a little bit.
This is around 115 to 123 Hz, sweeping the frequency.
And look at that drop!
Boing! It actually was able to escape.
It zoomed off, and when it zoomed off, it almost looked
like a solid, but I caught it there with my chopstick,
and on the chopstick without the shear, it turned back
into a pancake batter type fluid again.
And look what happens here.
Oops! There goes another blob.
There goes another blob.
This was all around 120 Hz.
[CAPCOM:] Don, that was absolutely amazing.
I think there's also consensus down here
that you should not show that to Robonaut
because shape-shifting forms combined with robot intelligence
on board, you may find yourself on the wrong side of a battle.