Name: 【TED-Ed】Magical metals, how shape memory alloys work - Ainissa Ramirez
Uploaded: 2014-08-14T06:25:59.000Z
Duration: 4 min 46 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Today we're talking about weird materials

that we use in space, in robots and in your mouth.

these are metals that remember different shapes.

we've got to talk about atoms and organizing.

Atoms are tiny bits of matter that you cannot see with your eye

yet they make up everything in our world,

from the chair that you're sitting on to your cell phone.

Atoms have some surprising ways of behaving too.

Well, imagine pulling one of your hairs out of your head

and whittling it like a stick 100,000 times.

One of those shavings  would be the width of an atom.

Now let's talk about atoms and organizing.

You may not know this, but atoms arrange themselves

similar to the way we humans arrange ourselves.

We call that seating arrangement a phase.

Other times they sit diagonal from each other,

sort of like seats in a movie theater or sports stadium.

When atoms move from one seating to another

You may already know about water's phases:

Many other materials have phases like that too.

OK. Back to those shape memory alloys we mentioned before.

When we say that the metals  remember their different shapes,

what we're really saying is they remember different seating arrangements

the metal moves from one shape to another.

Here I have a metal wire that  is made out of nickel and titanium.

and I'm going to make it switch between its different shapes

I'm going to wrap this wire around my finger

That wire returns to a straight line, when I heat it.

I'm going to wrap it around my finger, and heat it.

Here's a paper clip. When I heat it, I get nothing.

What we're seeing is the shape memory wire changing phases when it gets hot.

When the wire is cold, atoms  are in a diagonal arrangement,

like the movie theater seating, we talked about before.

and scientists will call this phase martensite.

the atoms moved into columns like airplane seating.

Scientists will call this phase austenite.

So when we added the heat,  the atoms shifted positions seamlessly,

They have this coordinated motion,  just like members of a tireless marching band.

Each makes a small shift, but all  together those small shifts

So that's pretty cool, but where do we use these materials?

on Mars. They're used to move  panels on the Mars rover,

Like our metal straightened when it was heated,

the metals holding the panels will move when electrically heated.

When we stop heating the shape memory metal,

the panel will return back, due to an opposing spring.

Back on Earth, shape memory alloys are used to open up clogged arteries

as stents, which are small collapsible springs

Shape memory alloys are also used to move robots,

toy butterflies, teeth in braces, and for a perfect fit every time,

shape memory wires are used  as underwires in bras.

By popping a bra into the dryer,  it'll be brand new every time.

So whether it's on Mars or in your mouth, small atomic movements

allows us to make materials  that make our world a better place.

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【TED-Ed】Magical metals, how shape memory alloys work - Ainissa Ramirez

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