Tiny Robot Arm Made With Origami Can Hold the Weight of Three Cats

origami drone
A drone equipped with the origami robotic arm reaches for a can in a narrow ditch. The arm was detailed in a paper published Wednesday in Science Robotics. Courtesy of Kim et al., Science Robotics

Folding something up tightly can save space. People who have lived in a tiny apartment know this. So do drone accessory designers, apparently.

Designs inspired by the paper-folding tradition of origami have captured the imagination of inventors. But by definition, stuff that can fold has weak points. Researchers in Seoul, South Korea, think they've figured out a way around that issue. They published their work on a stiff, origami-inspired, foldable drone arm in Science Robotics on Wednesday.

To build their arm, they used a box built from squares connected together in something called a Sarrus linkage. This linkage allows it to fold up only in a particular way—in this case, squares on the sides collapse outward as the squares on the top and the bottom push toward each other. The box also had a locking mechanism built in to keep it stable, and a wire pulled by a motor forces it to fold or unfold.

The box itself is pretty small—at about 9.75 cubic inches, it's about the size of a tennis ball. It weighs about 30 grams—basically the same weight as a light bulb. But if three typical cats wanted to get on top of it—cats' affinity for boxes being a well-documented phenomenon—it would still hold up under the weight.

Because of the way the system was designed, the boxes could be stacked to make a longer or shorter arm. If you top the arm off with a tool to grab things, then you can have some real fun. The Korean scientists tested their arm indoors as well as outside, sending a drop over a narrow ditch to pick up a bottle. The drone itself couldn't safely go into the ditch, so it sent the arm down like a slightly less ominous version of the claw from Toy Story.

To be fair, the arm still deploys pretty slowly and whizzing around too fast will make the arm unstable. A limit to how many boxes you can stack on top of each other does exist—too many, and the folding action starts malfunctioning, the authors noted in their paper.

Still, it's pretty cool looking. With a bit more work, it could be pretty useful, too.