Dear Dr. Universe: What is slime? How can I make it? -Nina, 10, Richmond, VA
Our world is full of slime makers. Slugs and snails leave behind gooey trails. Bacteria can create layers of slippery slime in water pipes. Even your body makes its own kind of slime. In our joints, we have slime that helps protect our bones.
My friend Nehal Abu-Lail is very curious about slime, too. She’s a researcher and professor in chemical engineering and bioengineering here at Washington State University. Part of her work is asking big questions about ways we can get rid of harmful slimes in pipes. She’s also interested in how we make slime so our joints move better.
Slime can behave in very interesting ways, she said. Depending on what kind of slime you are working with, it might flow between your fingers. But it also might behave more like a solid. You might even be able to roll it into a ball and bounce it.
Slime is in between a liquid and a solid. We call these kinds of fluids non-Newtonian fluids. When Sir Isaac Newton was studying liquids, he found that many flowed like oil and water. But we find things like slime flow a little slower.
Abu-Lail said the first thing you’ll want to do when making your own slime is decide what properties you want. Maybe it will be stretchy, gooey, slimy, or more solid. One way to get started is to use some Elmer’s School Glue, water, and borax detergent.
Dissolve about a teaspoon of borax in a cup of water. In another bowl, mix together about a half cup of glue and half cup of water. Then mix the two solutions together. You’ll notice slime starts to form in just a matter of seconds.
Abu-Lail explained that a very special chemical reaction is happening. The glue contains long chains of molecules. We call these polymers. And we can think of them like cooked spaghetti noodles, Abu-Lail said. They are pretty tangled up.
But if we dried the noodles a bit, and lined them up in a row, they would start sticking to each other pretty well. We could line them up next to each other in a repeating pattern. That’s kind of what happens when you add Borax to the glue. The Borax is a cross-linker. It takes those noodle-like polymers and links them together. What was once a free-flowing liquid is now thickened by polymers. Then things get slimy.
You can play with polymers and add different amounts of ingredients to see if you can change the properties of your slime. Twist it, mold it, stretch it. Try it out and see how two different things made up of different chemicals can create something totally new. Tell me about your slime science sometime at Dr.Universe@wsu.edu.