Have you ever mixed corn starch with water? If you have, you probably noticed how it oozed like a liquid when flowing across a surface, yet hardened like a solid if you suddenly struck it. That’s because the corn starch/water mixture is what’s known as a non-Newtonian fluid – the particles it’s composed of slide past one another easily when moving slowly, but jam against each other when forced to move quickly. Recently, a group of students from Cleveland’s Case Western University encased such a fluid within sturdy bags, to create a simple product that could be used to temporarily fill potholes in roads.
The students designed the device as their entry in an engineering contest sponsored by the French materials company Saint-Gobain, in which competitors were required to create a novel product from simple materials. Last week, they were awarded first prize.
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Although the composition of the fluid hasn’t been revealed, it is reportedly biodegradable and non-toxic. The students apparently had to try using a number of different particle sizes in order to achieve the right viscosity. It is stored in the form of a powder, within waterproof silicone-lined bags made out of a strong fiber such as Kevlar.
The idea is that city workers or perhaps even police officers would carry these powder-filled bags in their vehicles with them. When they came across a pothole that needed filling, they would simply open the bag, add water, reseal it, then lay it in the hole. Because the material would be in a liquid state at the time, it would simply press the bag into the uneven contours of the inside of the hole, while maintaining a flat upper surface. A piece of black adhesive fabric would be added over top to keep drivers from going around it, and presumably also to keep the bag from being flipped out of the hole.
When cars proceeded to drive over it, the speed at which they compressed the fluid would cause its particles to seize up, turning it into a solid that would support the car’s weight. Some of the prototype bags have been tested in high-traffic areas of Cleveland, where they apparently worked well, and lasted for over a week. They have yet to be tested in winter, although it’s believed that they shouldn’t have a problem with freezing temperatures.
Although the powder itself is said to be quite inexpensive, the bags themselves might end up costing around US$100 each. One bag could be reused in multiple potholes, however, which the students say would be much more cost-effective than using fresh asphalt every time – especially if those holes would just have to be permanently repaired later, anyway.
Several companies have reportedly already expressed an interest in the product. It can be seen getting repeatedly run over in the video below.
Source: Science NOW