In this video excerpt from NOVA’s "Making Stuff: Smarter", host and New York Times technology columnist David Pogue learns about the interesting behavior of some fluids with strange flow properties. Watch as he tries to run across a pool filled with Oobleck, a mixture of cornstarch and water that drastically changes its viscosity depending on how hard it is compressed. In a related activity, students mix their own batch of this “smart” material in order to explore its behavior and learn how Oobleck’s strange properties are helping materials scientists design new products and materials.
Making Stuff Smarter Activity (Document)
What Is Materials Science? (Document)
DAVID POGUE But in the search for smarter materials, engineers have taken a hard look at some liquids with very strange behaviors. They're called non-Newtonian fluids.
I travel to North Carolina, to the Lord Corporation, which manufactures one, but when I arrive, I have a burning question for Engineer Lynn Yanyo.
Forget non-Newtonian, what's a Newtonian fluid? She offers to show me one.
LYNN YANYO (Polymer Engineer) This is a Newtonian fluid. Take a look at that.
DAVID POGUE Turns out this Newtonian fluid is water.
What makes it Newtonian? I've never thought of it as Newtonian.
LYNN YANYO It makes it Newtonian because Isaac Newton discovered that there's a relationship between how hard it is to move it and the viscosity.
DAVID POGUE Viscosity meaning thickness?
LYNN YANYO The thickness, resistance to flow.
DAVID POGUE When you try to move something through water, the resistance is directly proportional to how fast you move it: twice as fast is twice as hard.
Now, that's kind of what you'd expect, but amazingly that's not true for lots of other fluids, the non-Newtonian ones, like ketchup. Ever wonder why it's so hard to get it out of a glass bottle?
That's because, unlike water, it thickens at rest, its molecules creating a weak structure that resists flowing.
Yes, I remember this from my hamburger days. Ladies and gentleman, it does not flow! Lynn is staking her scientific reputation and her hairdo on the non-flowingness of ketchup.
But if you can get it started, that structure breaks down, and the ketchup thins and flows.
Here's another non-Newtonian fluid, in fact, a lot of it.
Oh, here it comes, definitely a liquid.
This cornstarch and water mixture is known as Oobleck. The word comes from an old Doctor Seuss story. Oobleck dramatically changes its viscosity, or thickness, depending on how fast you try to move it.
Keep the action soft and it flows like a liquid, but hit it hard and it's solid enough that you can run across it.
This liquid, when I squeeze it tight, turns into a rock and then when I let go it turns back into a liquid, what is happening?
LYNN YANYO We like to call this, the Three Stooges effect.
DAVID POGUE That's not the scientific term! What do you mean the Three Stooges effect?
LYNN YANYO Well, you know when the Three Stooges tried to get through the doorway and they couldn't? The corn-starch doesn't want to get out of its own way. So, when you push on it really hard, it can't move out of the way fast enough.
And if you hit it really slowly, you can go right through it like a liquid.
DAVID POGUE So, it's a liquisolid. You know, it depends on the pressure, the speed or something.
LYNN YANYO It depends on the speed at which you try to move anything through it.
DAVID POGUE Oobleck's a lot of fun. Be sure to fill your neighbor's pool with it.
Oh, it's got me!
But non-Newtonian fluids designed into the right system can save your life.
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