The stuff of dreams

1. Dilatants - fluids that get more solid when stressed. The classic example is a mixture of cornflour and water - it's runny until you hit it when it becomes solid.

This video shows how that it possible to run across an apparently liquid pool of the stuff because your footfalls solidify it. If you stop, you sink.

I like this video better though - it shows how sound waves from a subwoofer produce interesting shapes in a dilatant. If you want to have a go yourself, try this recipe.

2. Auxetic materials - materials that get thicker when stretched. Pull them in one direction and they expand in another.

This video (.mov format) from Bolton University, UK, shows an auxetic foam in action. I like these because they are totally counter-intuitive - you just expect things to get thinner when stretched. Read more about them in a feature here or on this research page.


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