Oobleck is basically a mixture of cornstarch and water. It has the interesting property of going hard when pressure is applied. For example, it feels like a liquid when you swirl your fingers through it, but it becomes hard for a second if you punch it.
The common explanation for this is that the starch-water mixture is a suspension, and the starch particles "lock" when pressure is applied.
What exactly is the mechanism of this "locking"?