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An inexpensive, non-toxic sample of a non-Newtonian fluid sometimes known as oobleck can be made very easily by adding corn starch (cornflour) to a cup of water. Add the starch in small portions and stir it in slowly. When the suspension nears the critical concentration - becoming like single cream (light cream) in consistency - the so called “shear thickening” property of this non-Newtonian fluid becomes apparent. The application of force - for example by stabbing the surface with a finger, or rapidly inverting the container holding it - leads to the fluid behaving like a solid rather than a liquid. More gentle treatment, such as slowly inserting a spoon, will leave it in its liquid state. Trying to jerk the spoon back out again, however, will trigger the return of the temporary solid state. A person moving quickly and/or applying sufficient force with his feet can literally walk across such a liquid.

Shear thickening fluids of this sort are being researched for bullet resistant body armor, useful for their ability to absorb the energy of a high velocity projectile impact but remain soft and flexible while worn.

http://www.youtube.com/watch?v=f2XQ97XHjVw
http://www.youtube.com/watch?v=dYnZ5vNgDWw

http://en.wikipedia.org/wiki/Non-Newtonian_fluid

Filed under: Things We Like on August 9th, 2007