Here’s a fluid dynamics video that shows us a water droplet falling onto a hydrophobic needle. It’s pretty cool! Instead of spreading into a puddle, the drop turns into a hollow crown of moving water.
Here we see a fight between a droplet of water, full of molecules that attract each other, and a hydrophobic needle, which is driven into the heart of the droplet and attempts to drive the molecules apart. The video gets especially cool around the 1:46 mark, where we see, simultaneously, the way a droplet behaves when it hits the flat ground, and the way a droplet behaves when speared by the needle. I can’t decide which I like better, when the drop stays together as a ring, or when the drop breaks up into wildly flying smaller droplets. You?
