A bit of summer rain may be a nice hot-weather reprieve for a human, but for a mosquito, it's a minefield. And while your heart may not bleed for the little bloodsuckers, scientists say understanding how this insect's small frame helps it survive collisions with objects many times its size could help us build more robust flying robots.
Engineers and biologists at Georgia Tech shot jets of water at containers full of mosquitoes and captured high-speed video of their close encounters with the droplets. They reported their results Monday in the journal Proceedings of the National Academy of Sciences.
To a mosquito, these raindrops are like comets -- they're 50 times heavier than they are and falling at about 1,000 mosquito body-lengths per second, senior author David Hu said in a telephone interview.
In a normal storm, a mosquito will probably be hit about once every 20 seconds, and each drop hits them with a force that's 100 times their own weight, according to Hu.
But thanks to their small size and strong exoskeleton, the insects are able to shake off impacts that would obliterate a human if they were struck by a similarly sized force.
Some things just don't scale -- muscles seem to get stronger and materials seem to be enhanced by virtue of being small, Hu says.
After the impact, the mosquito tends to cling to the raindrop, falling along with it for a small distance; it eventually peels itself off the drop after a fall of between 5 and 20 times its own body length. Hu says his team thinks that the impact and freeing happens too quickly for mosquitoes to be doing anything to actively get away from the raindrop. Instead, the way their bodies are designed -- long legs and long wings helps them disentangle themselves automatically.
That sort of design could be applied to small flying robots, Hu says. The U.S. military is especially interested in developing these kinds of 'micro air vehicles' for use in reconnaissance and spying. Many such instruments are in development -- one of the more recent successes is a robotic hummingbird that can fly up to 11 miles per hour, hover for up to eight minutes, and withstand wind gusts of five miles per hour.
But these man-made bugs and birds often can't cope in truly bad weather. The secret to making hardier robots may lie in making them tinier.
When you make things smaller you get robustness for free, Hu says.