Taking a dip just got a bit more harrowing. Engineers have debuted a robotic jellyfish that swims faster than previous models. The 16.4-centimeter-wide undulator, dubbed Robojelly and which mimics the crustacean-eating moon jelly (Aurelia aurita), pulses like the real thing thanks to faux metal alloy muscles running down its sides that contract when zapped with an electric charge. The new Robojelly design, rolled out this week at the annual meeting of the American Physical Society's Division of Fluid Dynamics, incorporates an unusual anatomical feature: a jellyfish mud flap. When a real moon jelly throbs, its entire umbrella-shaped bell pulses in unison except for one small ribbon of tissue at its lower margin. This margin doesn't flex much on its own but, instead, passively follows along as the invertebrate tightens and relaxes. With such a lagging flap built in, Robojelly can now create stronger and more sustained vortices with each pulse, giving it a bigger push in water. The improvements make Robojelly a better imitator of living jellyfish, although it can't sting—yet.
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