by Rachel Vowcicefski
SC Copy Editor-in-Chief
Non-Newtonian fluids such as silly putty are made from both cornstarch and water, which have properties of liquid and solid. Although it may be fluid-like when it’s held, when pressure is placed on it, it becomes hard like a solid. Using this interesting property, a group of college students has figured out a way to use this cornstarch concoction to fill potholes. Scientists call substances like silly putty non-Newtonian because the viscosity, or resistance, of the fluid changes in response to the forces that are applied to it.
This is in contrast to Newtonian fluids, which maintain their fluid state regardless of the change in force applied. Some examples of non-Newtonian fluids are mayonnaise, ketchup, silly putty and even blood. Although these substances seem very different, they all contain some sort of particle, and the interaction of those particles explains their behavior.
The type of material the students chose is the opposite of ketchup and mayonnaise, which sticks together and gives way under stress. The putty has a shear-thickening affect, meaning that when a shear stress is applied, like by a tire, it becomes stiffer and resists flowing out of the hole. This occurs because when a light force is applied, the particles slip past each other, but when they are attacked by a strong force, the viscosity increases because the particles do not have a enough time to rearrange, thus pushing back and resisting movement.
Undergraduates at Case Western Reserve University in Cleveland, Ohio entered their idea into an engineering contest sponsored by the French materials company Saint-Gobain that centered on the design of a novel product using simple materials. At the beginning of last week, they took the first prize.
He and four other students decided on the everyday problem of potholes and then on using a non-Newtonian fluid as a solution because of its unusual physical properties, which is a perfect solution for those pesky potholes. The students worked with different-sized particles until they found the right concoction that gave them the viscosity they were looking for.
Currently, potholes are mended using hot asphalt that is bad for the environment and dangerous for the workers.
With their new material, the students created a powdered mixture that is stored in specially designed waterproof Kevlar bags that are lined with silicone. Simply add water, reseal the bag and throw it in a pothole and the problem is solved. Anyone could throw these bags into the holes, but crews would have to come around and cover the top of the holes with black adhesive fabric so that the drivers will not attempt to avoid them.
The students have successfully tested their creation in potholes in high traffic areas and found that the bags hold up well for long periods of time. As far as the winter goes, the students have yet to test the bags in these conditioned but they are certain that the bags will hold up since they were designed to take a beating in diverse temperatures. These bags are only meant for temporary use to cover the holes until the roads are repaired. Once the repair is made, the bags can be removed and reused over and over again, making the overall cost quite low.
Upfront, the cost may seem a bit high, but the money saved in the long run will benefit the entire community. Since the students plan to patent their invention, they can only report that the material is safe and biodegradable. So if the bags leak or tear, the contents will not harm the environment.
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