// Honestly this is one of my favorite Zak moments, because he’s just so playful.
Zaknafein is not a nice guy. As a matter of fact, before and after he trains Drizzt, he is one mean motherfucker. He cuts out the tongues of high priestesses with a whip, blind. But as soon as Drizzt shows up, Zak is all warm and fuzzy. He’s still full of cocky sarcasm, too, but for once his smiles are actually GENUINE.
If you dropped a water balloon on a bed of nails, you’d expect it to burst spectacularly. And you’d be right – some of the time. Under the right conditions, though, you’d see what a high-speed camera caught in the animation above: a pancake-shaped bounce with nary a leak. Physically, this is a scaled-up version of what happens to a water droplet when it hits a superhydrophobic surface.
Water repellent superhydrophobic surfaces are covered in microscale roughness, much like a bed of tiny nails. When the balloon (or droplet) hits, it deforms into the gaps between posts. In the case of the water balloon, its rubbery exterior pulls back against that deformation. (For the droplet, the same effect is provided by surface tension.) That tension pulls the deformed parts of the balloon back up, causing the whole balloon to rebound off the nails in a pancake-like shape. For more, check out this video on the student balloon project or the original water droplet research. (Image credits: T. Hecksher et al., Y. Liu et al.; via The New York Times; submitted by Justin B.)