A non-Newtonian fluid is one of the more intriguing substances in science. It is a fluid that has a changing viscosity depending on the kind of stress that is applied to it. This is different from a Newtonian fluid (like water), where its behavior can be described just by looking at the temperature and pressure, and not the forces being exerted on it. The most common form of a non-Newtonian fluid is cornstarch mixed with water.
Different forces will make a non-Newtonian fluid perform in different ways. For example, exerting a sudden force on a non-Newtonian fluid will cause the atoms in the said fluid to rearrange themselves and behave in much the same way as a solid. This means, if a stick is suddenly and forcefully slammed into a non-Newtonian fluid, it will not go through. It will be like pushing the stick into a solid. But if the same stick is submerged into the fluid slowly, it will be able to go through because the non-Newtonian fluid will act like a liquid. Now, if the submerged stick is suddenly pulled out, the fluid will again act like a solid and it will try to move with the stick, like it has solidified around the stick.
Non-Newtonian fluids are being studied by scientists because it offers them a glimpse of how fluids exist and behave. Other interesting types of fluids that are also being studied are plastic solids, viscoelastic fluids, power-law fluids, and time-dependent viscosity fluids. These are also different fluids that behave in strange ways. But none of these has the potential for real-world applications as much as non-Newtonian fluids.