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This Robo-Snake Learned How to Climb Sand Dunes From Real Snakes

It can chase you up 20-degree slopes.

Ever tried to run up a sandy slope? It's not easy— for us, or for robots. But for desert-dwelling snakes, it's a piece of cake (let's hope you've never tried to run up a sandy slope while being chased by a snake). The sidewinding action of rattlesnakes was the biological inspiration for the first snake robot that can climb sand, which you see above.

But, perhaps most interestingly, the research ended up being a breakthrough not just in robotics, but in zoology, too.

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Daniel Goldman, of Georgia Tech, says that, as his team (he was the zoologist and physicist, Howie Choset was the roboticist) was able to better recreate the movements necessary to get a snake robot to climb sand, they learned about how snakes originally evolved their sidewinding abilities and learned more about the body mechanics that makes snakes such good sand dwellers.

"The goal of this study was to learn about the biology of a snake," Goldman, author a new study in Science, told me. "We thought, if we get lucky and find something while studying the snakes that's implementable to make the robot better, well, then we'll do it."

The team did, in fact, do that. When sidewinding up a slope, snakes keep themselves in two "planes" and move in a wave movement that Goldman says allows it to have "no slip locomotion on sandy slopes." Never before did scientists have a model of the physics of how that technique worked. Now, they do.

In an accompanying perspective, John Socha of Virginia Tech called it a "reciprocally illuminating process."

"The robot was used as a model to probe the snake, and the snake was used to understand and improve the robot," he wrote.

Most interestingly is the fact that, when sidewinding snakes amble up a sandy slope, they don't dig deeper into the sand, which you might think would help them slowly power up, inch by inch. At least, that was the theory—when you or I run up a slope, we push more and more sand away and dig deeper to keep from slipping.

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Image: Nico Zevallos & Chaohui Gong

But moving like that also expends a lot of energy. Instead, snakes stay lower to the ground, elongating themselves and pushing less of their bodies off the ground.

"As the slope became steeper, the snake laid down more body, increasing its purchase on the sand until nearly half the body was in contact," Socha wrote.

Armed with that knowledge, Choset and his team were able to modify their own robot, which had previously just been able to sidewind along flat sand, until it was able to make its way up 20-degree slopes.

Also of note: Not every snake knows how or has the muscle control necessary to sidewind—even when they're relatively close relatives of rattlesnakes. The team tested 13 species of pit vipers, none of which were able to move up the hill.

You can imagine some military or rover applications coming out of this in the future: "The Mars rover goes up hills very slowly and very deliberately," Goldman said. "It has no where near the performance of something like this that sidewinds."