How an insect that uses its butt to wipe away pee drops can keep your smartwatch dry

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The glassy-winged sharpshooter is an insect as impressive as it pees that it could inspire more efficient designs for water-resistant devices.

Saad Bhamla was in his vegetable garden in Atlanta, Georgia, when he first noticed the feat. The sniper forms neat, round puddle droplets that he shoots away at lightning speed. Bhamla, an assistant professor of biomolecular engineering from Georgia Tech, pulled out his iPhone to shoot some slow-motion videos.

“The more I zoomed in, the more I realized it was doing something interesting,” says Bhamla The edge.

“The more I zoomed in, the more I realized it was doing something interesting”

It turns out that the sniper achieves something with his urine that has not yet been documented in any biological system – a phenomenon called superpropulsion. How the sniper does this is described in a research paper Bhamla and colleagues published this week in the journal Nature communication. And it might also help people figure out how to achieve super propulsion – not with piss but with smartwatches and other devices that dry themselves off.

Simply put, superpropulsion allows an elastic object to fly faster than the thing launching it. Accurate timing between the soft object and its slingshot gives the object an energy boost. To understand this phenomenon, think of an Olympic diver, Bhamla explains. An experienced diver could time a jump to get the maximum resonance energy from the springboard.

After capturing the videos with his iPhone, Bhamla and his colleagues turned to high-speed cameras and microscopes to get a closer look at the sniper. What they found was an anal stylus, also known as a butt flicker, which is key to the insect’s unique way of getting things done. The butt flicker moves backward to make room for incoming pee, allowing it to form a droplet on the insect’s tail end. At the same time, the flicker compresses the droplet, allowing energy to build up through surface tension.

Once the droplet is the right size and shape, the flicker will rotate back another 15 degrees. Then it shoots the drop like a pinball machine. The butt flicker is incredibly fast, accelerating over 40 Gs, which is 40 times faster than the acceleration of a sprinting cheetah. What’s even more amazing is that the puddle flies at an even higher speed than the butt flicker – the telltale marker of super propulsion.

As a plus, the tactic is also energy efficient. After all, the drop moves faster than the slingshot that launches it. Snipers actually pee this way to save energy because they piss a lot of. Sharpshooters drink and urinate up to 300 times their body weight per day because they have a super-low-calorie, low-nutrient diet of plant sap. And he has to dispose of his pee to prevent the drop from sticking to it like a dollop of maple syrup.

What does this have to do with a smartwatch? For example, the Apple Watch’s Water Lock feature can squirt water out of the device after swimming. But as far as Bhamla knows, devices like this don’t yet use superpropulsion. If engineers can learn from the sniper, they may be able to design more efficient water drainage systems for gadgets. This way you also keep your watch dry and charged for longer. The same kind of technology can be used in hearing aids or anything else you want to make water resistant.

The researchers tested the method with loudspeakers.
Image: The Bhamla lab

Bhamla and his team tested the sniper’s tactics by bouncing water off loudspeakers on their kitchen counters. They used the vibrations of the speakers to compress tiny droplets, building up surface tension. With precise timing, they could then launch the droplets at high speeds.

While it sounds apt, this nifty trick isn’t what earned the insect the nickname “sharpshooter.” It is best known in the US as a pest to farmers. The bite marks can look like tiny bullet holes in leaves and it can transmit disease from one plant to another. The copious urination can also whitewash fruits.

Bhamla hopes his research can inspire more people to look at insects from new perspectives. “I think it’s going to get kids young at heart and getting older, going into their backyards and enjoying themselves,” he says The edge. “It’s a lot of fun. That’s good enough for me.”

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