Undergraduate engineering students at Case Western Reserve University just won a contest sponsored by French materials company, Saint Gobain, with their idea for a pothole patch. The students wanted to address an annoying problem that was found worldwide and settled on coming up with a solution for potholes. Their design for a temporary pothole patches uses pouches filled with a non-Newtonian fluid. In order to understand why non-Newtonian fluids are cool, you first have to understand viscosity. A fluid’s viscosity tells how well it’s able to resist a change of shape when force is applied to it. It’s basically how thick a fluid is. Thick fluids have high viscosity and require more force to change their shape than a thin, low viscosity fluid. This quick video is a side by side comparison of two fluids with very different viscosities:
A Newtonian fluid is one that holds a consistent viscosity when force is applied to it. What makes non-Newtonian fluids interesting is the fact that their viscosities change when force is applied to them. Most of the common non-Newtonian fluids like mayonnaise, ketchup and blood have a lower viscosity when force is applied to them. This is because they have particles suspended in the fluid that are attracted to each other. Once these particles are separated by an applied force, their attraction no longer contributes to holding the fluid together. Here’s where things get a little crazy. There are some non-Newtonian fluids that increase their viscosity and get thicker when force is applied to them. A mixture of corn starch and water is the most common example of this. The stuff basically becomes a solid when you apply a force to it. Check out the high speed footage of it in action from Discovery Channel’s show Time Warp:
The corn starch and water trick has been around for a while and it’s a lot of fun to play with as evident by this Boston University Engineering block party:
Major kudos goes to the engineering students of Case Western for actually coming up with a simple and practical application of non-Newtonian fluids. What they want to do is fill kevlar pouches with a mixture similar to corn starch and water and use them as temporary patches for potholes. The fluid nature of the pouches will allow them to conform to the shape of the pothole and provide a smooth road surface. As soon as a car drives over it, the force will cause the non-Newtonian to harden and support its weight. This is great because anybody can throw down one of these pothole patches in seconds and it will restore the road surface until a full repair can be made. It’s definitely one of those “Why didn’t I think of that?” ideas.
Just as one last interesting note, check out this video of a puddle of non-Newtonian fluid inside of a subwoofer playing dubstep. When the fluid gets shot up by speaker, it’s a solid and then it returns back down to the puddle as a fluid. Compare this reaction to the water drops in space.
Source: Science Now