(Photo : Duke University)
Cicadas, well known for their unique sound and prominent eyes, have helped researchers stumble upon a rather unique cleaning agent: dew drops.
After arising from their slumber (some species lay dormant for up to 17 years before hatching), the cicadas have some in-house cleaning to do before taking off. The insects, it turns out, rely on dew drops to help the dirt jump off their water-repellant, or superhydrophobic, wings.
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"Most cicadas are unable to clean their own wings because of their short appendages," said one of the researchers, Gregory Watson from James Cook University. "Furthermore, these insects commonly live in areas where there is little rain over an extended period of time. However, the areas are humid, which provides the tiny dew droplets needed to 'jump clean' their wings."
By using high-speed video, researchers were able to pinpoint the driving force behind the "jump clean." As dew drops coalesce, their merged form leaps off a superhydrophobic surface simply due to the surface energies stored in the initial separate, tiny drops. The scientists are hoping that this will lead to more effective cleaning methods for superhydrophobic surfaces across the board.
"The ability of water-repellant surfaces to self-clean has conventionally been attributed to rain droplets picking up dirt particles," team leader Chuan-Hua Chen said. "We have found, however, that the self-propelled jumping motion of the dew drops is very effective in dislodging contaminating particles, regardless of the orientation," Chen said. "These new insights can help guide the development of man-made surfaces that are not dependent on any external forces and are therefore truly self-cleaning."
You can read the full published study, titled "Self-cleaning of superhydrophobic surfaces by self-propelled jumping condensate," in the Proceedings of the National Academy of Sciences of the United States of America.