If you ever find yourself stuck in a disaster zone, your rescuer could take on some unexpected forms, like a drone or a cyborg cockroach – and now we can add a soft robotic snake to the mix. A Stanford team has developed a flexible robot that grows like a vine, squeezing through rubble to find trapped survivors and even delivering water to them.

Rather than a rigid robot rummaging through the rubble, the Stanford snake starts life as a rolled-up, inside-out tube made of soft material, with a pump at one end and a camera attached to the other. When it's fired up, the robot inflates and grows in the direction of the camera end, while the other end stays put. It's a mobility method closer to that of plants than animals (or robots, for that matter), and the team wanted to explore how this technique could be used.

"Essentially, we're trying to understand the fundamentals of this new approach to getting mobility or movement out of a mechanism," says Allison Okamura, senior author of the paper. "It's very, very different from the way that animals or people get around the world."

The robot is able to turn corners by inflating one side more than the other, and it decides where to go from the camera and algorithms that interpret what it's seeing. That allows it to follow complex paths of its own choosing to reach a designated goal.

To test their creation, the Stanford team ran the robot through a series of obstacle courses, and it successfully navigated its way through flypaper, glue and nails, before climbing up an ice wall. It didn't get through unscathed, but being punctured by the nails didn't stop it, thanks to its unique method of movement. Since the puncture site doesn't move, the nail keeps the hole plugged while the tip of the robot continues to extend.

"The body lengthens as the material extends from the end but the rest of the body doesn't move," says Elliot Hawkes, lead author of the paper. "The body can be stuck to the environment or jammed between rocks, but that doesn't stop the robot because the tip can continue to progress as new material is added to the end."

The growing robot's list of other abilities is as long as its own body. It was able to inflate itself to lift a 100-kg (220-lb) crate off the ground, squeeze through a gap just a tenth of its own diameter, spiral around on itself to build a free-standing structure, and pull a cable through its body. All of these functions could make it a useful partner in disaster relief, or just day-to-day building maintenance.

The current prototype is made of cheap plastic, but with the concept proven the researchers plan to try making future versions out of tougher materials like Kevlar. They could also grow using pressurized liquid instead of air, letting them deliver water to trapped people or to put out fires, and eventually be scaled down to a size that could see them moving through the human body less invasively.

The research was published in the journal Science Robotics, and the growing robot can be seen in action in the video below.

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