Macrocosm: An Origami Wheel Trekks A Path Over Unsteady Ground

Randall Kamien

When you think of origami, your mind may jump to paper cranes made of colorful paper. When Dae-Young Lee thinks of origami, he thinks of transportation and innovation.

A research team led by Dae-Young Lee at Seoul National University, in conjunction with Hankook Tires, recently rolled out a wheel, made entirely of aluminum, that can withstand the weight of a passenger car.

The study, published in Science Magazine under their robotics section, reflected on origami’s widespread use within the world of ‘soft robotics.’ Soft robotics deals with robots constructed from highly compliant materials, similar to those found in living organisms. A soft robotic arm would be tensile and able to maneuver delicate objects with ease, though it would be harder to construct and control than a traditional robot. Common pop-cultural touchstones of soft robotics are Baymax from Big Hero 6 (a robotic creature with a soft, inflatable vinyl exterior) and Doc Oc from Spiderman: Into the Spiderverse, who uses octopus-like robotic limbs to move around and interact with her environment.

Soft robotics can be useful for limb-like, delicate movement, but it can also be useful for transformative robotic work. Previously, the folds of origami were used to create small toys and amusements - flat sheets of metal or plastic that could fold into a traditional looking ‘robot’ that could run, climb, and even swim. These small robots mark a definite beginning for origami’s work in robotics, but nowhere near an end said Lee.

“I want to prove that this origami structure can be used for more practical and extreme applications,” said Lee, the lead author of the piece. “When a robot is this close to our homes and our lives, we should be maximizing its efficiency.”

How can origami maximize efficiency?

The strength of origami comes, naturally, from its folds. The explanation for this comes in a simple experiment.

Tear a piece of paper in half. Any piece. (Though maybe not your tax returns.) Now, take a piece of paper and fold it into quarters, then eighths. Try to tear it now. It’s much harder, isn’t it? This folding thickens the paper, and, more relevant for Lee’s research, it increases the stiffness of the paper. If that folded piece of paper were to be suspended between two blocks and you were to put a quarter on top of it, the paper would be able to withstand this weight. The paper is flexible, still (try folding your experiment instead of tearing it), but bears a tremendous amount of weight relative to its size. A self-locking origami design technique was recently revealed to hold thousands of times its own weight.

Origami relies on this same principle for its structurally sound and flexible art. A paper crane stands on its own and can stay like that for quite a while without dust or stray wind denting its form. The origami wheels are the same; Lee even started his thought process for the wheel on folded paper.

There’s one distinct difference between a paper wheel and a car wheel, though. A car wheel needs to have a degree of thickness in order to support the frame of a vehicle. This meant that Lee’s research team had to rethink their wheel’s material multiple times over and work closely with a local car company to actually construct the device.

“I am an academic,” Lee said, chuckling. “I have no experience with wheel materials. Hankook Tires has a lot of databases on the material, how to handle the materials, the toughness, the flexibility… they handled the tire. We handled the origami.”

After that, the process became easier, but Lee wanted the process to expand even further. He didn’t just want a wheel that transformed into two functional states. He wanted the wheel to be functional throughout - whether it was transforming or not. After all, a wheel that ceases to function while transforming will end up crumbling under the weight of whatever it’s bearing. 

The team then had to put the thick aluminum membrane together with a design that accommodated it and allowed it to hold its shape while in a state of transition. They chose a thick wireframe, also made of aluminum, to keep the frame light while holding it steadily together. A hard fabric was draped over to keep the wheel steady and protect it from chipping. Finally, after 3D printing and assembly with rigid facets, the wheel was able to adapt to changes in elevation, unstable platforms, and smaller crawlspaces. You can even watch it in action.

What could this mean for the future?

Lee doesn’t know if this wheel has the legs for mainstream vehicles just yet. It’s still in its infancy, and the transition between two states does take a few seconds longer than most cars behind the driver have the patience for. But the applications for this work extend far beyond the asphalt.

“Many things can be applied to this,” says Lee. “A temporary structure in the road, or maybe even transformative furniture.”

Any vehicle that has to deal with unexpected terrain would find these transformable wheels useful. Though our motorbikes move a bit fast for it, a rover would find them perfect for a drive over Mars’ rocky landscape. With more investment into these concepts and the introduction of industrial rubber to the equation, these wheels could become the new norm for all-terrain vehicles. Lee anticipates that this application could eventually lead to space rovers that can completely package and unpackage themselves, along with parts of space stations that fit snugly into small satellites. These innovations could save space on extremely space-limited flights.

Whatever outlook comes, Lee and his team are incredibly invested in this new soft robotics technology.

“It’s crazy to say, but we just reinvented the wheel!” said Lee.