On drops of water through the air – knowledge

They are true jumping artists: Springtails, only millimeters in size and wingless, often live on the surface of streams, swamps or ponds and can jump more than ten times their body size. So far, researchers have assumed that the flight and especially the landing of springtails is uncontrolled and unpredictable. But that is obviously wrong: like a research team from the Technical University of Georgia now in the journal Proceedings of the National Academy of Sciences (PNAS) reported, the little animals stabilize their bodies during their jumps with the help of a water droplet. They take off in milliseconds, turn and reorient themselves in the air thanks to this droplet, and then land in a controlled manner on the water surface. These precise leaps would also protect them from predators. Based on the new findings, the researchers have even succeeded in developing small jumping robots.

Springtails are the most widespread, common, and diverse group of non-insect hexapods, according to the report. They are known for their important role in soil ecology and their unique ability to catapult themselves into the air. The researchers have now investigated this jumping behavior using the example of the springtail “Isotomurus retardatus” with the help of video recordings, among other things. They found that Animals first adjust their posture and the angle of their jumping organ, the furcula, when they take off. At the same time, they absorb a drop of water with a tubular organ on the underside, the so-called collophor.

Robots constructed according to this model also landed safely – at least most of the time

In the air, the springtails then curve their bodies into a U-shaped posture that creates an aerodynamic torque, causing them to right themselves just 20 milliseconds after take-off. According to the researchers, it is the fastest erection in the air of all the wingless animals studied. According to the study, they lower their center of gravity with the help of the water droplets absorbed by the collophor. When they landed, they generated a capillary wave and anchored themselves to the surface with the collophor, which prevented them from bouncing off.

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“Nobody has ever shown experimentally what the collophore is really for, and we show that it is important for their survival,” said Víctor Ortega-Jiménez, one of the study authors, according to a statement from the Georgia Institute of Technology. “They need it for stability, for taking off control, but more importantly they can land perfectly like an acrobat.”

The researchers also found that springtails can control their take-off angle and speed. They created a mathematical model to use a computer simulation to determine how precise these jumps are. They also used dead and live springtails in a wind tunnel to study their ability to right themselves in the air.

The researchers then built small ones in collaboration with Ajou University in South Korea robotto replicate their experimental and computational observations in a real environment. It turned out that the robots, which were modeled on springtails, actually landed safely in three quarters of their jumps. Such robots could expand the capabilities of robots in new terrain, such as open water surfaces in our planet’s lakes and oceans, explains Je-sung Koh of Ajou University.

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