Staying dry to stay alive: The ant raft and other water-repellent systems
October 17, 2012 - 11:00am
Marcus Nano Building Room 1116
We present a series of experiments demonstrating how animals stay dry. These adaptations are necessary for survival in rain and other wet environments. During flash floods, fire ants weave hydrophobic rafts with their own bodies in order to keep their colonies dry. We discuss their method of self-assembly and present a model that predicts their construction rate. To survive raindrop impacts, flying mosquitoes take advantage of their low mass, which prevents drops from splashing upon impact. The resulting force applied is 100-300 gravities, quite possibly the largest survivable force in the natural world. Animals much larger than insects employ active mechanisms to shed water. Mammals across four magnitudes in mass can shake off 70% of the water on their bodies in fractions of a second. We show that wet mammals shake at tuned frequencies to dry and present a scaling law relating animal size and frequencies required to dry. In this talk, the audience will learn the basics of modeling and experimentation with surface-tension phenomena.