A drizzling, misty rain may be harmless to man; however, such rain may be apparently fatal to small flying creatures such as mosquitoes. Perhaps hard to imagine, however, the average weight of a raindrop can approximately be 50 times heavier than the average weight of a mosquito! In comparison, a mosquito flying in a drizzling rain is like a person walking on the street, trying to dodge huge balloons filled with water – each weighing at least 500 lbs! Despite this, surprisingly annual precipitation does not seem to have effect in controlling the population of mosquitoes – at least this is not happening in Florida. So, what is the underlying mechanism that allows such tiny, flying creatures to survive the impact of a massive raindrop?
A research conducted by Dickerson et al. in Georgia Tech and published in the Proceedings of the National Academy of Sciences (PNAS)concluded that, rather than attempting to dodge incoming raindrops (which is almost impossible), mosquitoes employ two main strategies to reduce harm when hit by raindrops. Firstly, upon impact, rather than attempting to counteract the momentum of a raindrop, the mosquito tries to infuse with the raindrop and falls with it. Since the weight of mosquito is only negligible comparing to the raindrop, this factor greatly attenuates the impact brought on by the raindrop. Secondly, the mosquito will try to lean towards one side, thus allowing the raindrop to slide off its surface. This is thanks to the hydrophobic hairs that cover most of this body, which allows for a quick separation between the mosquito and the raindrop allowing the mosquito to continue its flying trajectory. In contrast, a mosquito that falls onto the ground with a raindrop will eventually perish by drowning since, in such cases, the mosquito is fully submerged with water and cannot easily separate from the water pool due to surface tension. Hence, the key for its survival is to get rid of the raindrop before it hits the ground.
Such natural characteristics of mosquito may inspire scientists in designing the next generation of quadcopters or similar flying robots. Now, we already have quadcopters that can fly in rain, however, their robustness and loading capacity is both extensively reduced under such conditions, not to mention the difficulties present to develop a surveillance quadcopter that can fly under harsh sea conditions (which may be necessary for any sea-based rescue missions). Designing special flying programs that will rapidly reduce the output throttle to reduce momentum clash upon detecting any large water mass impact and by adding a hydrophobic layer will allow the quick separation of the aircraft from the large quantity of water mass. This type of flying robot may prove to be able to withstand harsh sea conditions and become invaluable for maritime guidance, surveillance, and rescue.
References:
Andrew K. Dickerson, Peter G. Shankles, Nihar M. Madhavan, and David L. Hu (2012). Mosquitoes survive raindrop collisions by virtue of their low mass. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1205446109
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