Non-Newtonian Fluid


Art by Yasmeen El-Jayyousi

Adam Schoelz

Art by Yasmeen El-Jayyousi
Have you ever consumed a non-newtonian fluid? The answer may surprise you, which is cliche journalism-speak for “yes, even if you think you haven’t.”
Although they sound like something that gave the Hulk his superpowers, non-newtonian fluids are simple, expectation-defying liquids and with no gamma radiation. Bascially, a NNF is a fluid (well, obviously) that differs in flow properties from Newtonian fluids (well, obviously). Since this is a circular definition, I’ll provide a simple example: cornstarch and water.
Yes, that most fantastic of toys, that marvelous discovery in childhood that simple cornstarch and plain water, when combined, form a magical liquid that is ALSO a solid. The cornstarch in the water is made of long molecules — polymers. When the goo moves slowly, the polymers get along well enough and slid past each other easy. When things get cramped, however, the polymers get all mad and freeze up. Thus, you can do stuff like this. In the video, the speaker is hitting the goo at 30 Hz, so it moves up and around due to the rapid oscillation of force.
So I said at the beginning that you’ve probably eaten a NNF, and moreover probably remarked on its unique properties. Probably not cornstarch-water goop, however. The non-newton I and many others enjoy is far more tasty — ketchup.
But wait!– you say, dazed and confused. When I hit ketchup it doesn’t solidify, it goes everywhere! That’s not the NNF you’ve been talking about.
And I’d say why are you hitting ketchup? Seriously, what benefit comes of that? What did ketchup ever do to you?
And also: exactly.
Because as we all know ketchup in glass bottles seems to fall out in globs, barely moving and then moving a lot. See where I’m going with this?
Ketchup is the reverse of the cornstarch-water gloop. Instead of moving slower when spurred to action, it’s slow to start but begins to move faster when it’s already moving. This is called shear thinning — gloop, on the other hand, is shear thickening — and it’s the reason glass ketchup bottles suck.
In the end, what this means to you is that mixing cornstarch and water isn’t just a good idea, it’s a great idea. Do it right now, seriously. Make a giant vat and dance on it, or look on YouTube for the video of cornstarch-water on a speaker cone and then make that. Really, it comes down to how much work you’re willing to put into it, and as high school students, I’d understand if you chose the vat.
By Adam Schoelz