If you’ve ever made a cootie catcher or paper airplane, then you know how useful folding can be as a construction technique, especially if you’re trying to annoy your grade school teachers.

But say the only thing you can make out of origami is a rock. Like... pretty much. Before you practice your free-throw on the recycle bin, take a closer look, that paper rock has all kinds of interesting physical properties. For one thing, it’s very strong. You can only compress standard printer paper by hand to a point where about 90% of it is still air.

It’s also a little springy, which is why crumpled paper is such a great packaging material. The ball-rock's strength comes from flat sections of the paper that are layered together to form thick walls. Those walls are supported by stiff ridges that brace the ball in different directions.

And that’s just what you can get from folding randomly. With careful planning, you can do way more, like transport bulky things in small packages and easily change something’s shape. That’s led to a deluge of recent research into things that fold, collapse, or expand, all inspired by origami.

With folding, you can compress bulky objects into a small space without sacrificing too much structural integrity. That makes it great for transporting things to places that are hard to get to, like the sites of natural disasters, outer space, or even the inside of the human body.

Natural disasters can damage infrastructure like roads and bridges at a time when they’re needed most. Victims can be isolated from emergency aid when every minute counts. With that in mind, in 2015, a team of researchers from Hiroshima University in Japan designed an emergency bridge that can fold small enough to fit in a trailer.

It's a type of truss bridge, the kind made from beams connected to form strong shapes like triangles. If you've ever made a bridge out of spaghetti and marshmallows, you made a truss bridge. This kind of bridge takes advantage of the principle that beams, like strands of spaghetti, perform well when they’re pulled or compressed along their length, even though they’ll break or deform if they’re bent.

To prevent bending force on its beams, it’s important that the connection points of a truss bridge work like pin joints, which rotate like your knee — meaning that they can only swing back and forth along one path. Pin joints are used in truss bridges so that if there’s a force pushing sideways on a beam, it’ll rotate around the joint instead of bending in the middle. Normally, the beams in a truss bridge are arranged so that overall, the beams don’t rotate too much and the bridge is stable.

But this foldable bridge is designed so that all the pin joints are free to rotate when the bridge is being folded or unfolded. Once you lock the base of the bridge in place, you end up with triangles along the sides of the bridge that constrain the rotation of the pin joints. That’s how you end up with a stable, strong bridge ready for traffic.

Within an hour, this bridge can be expanded to more than 20 meters and easily hold the weight of a moving car. And since the bridge just unfolds into place, practically anyone can build it safely. No complicated assembly is required.

NASA also needs things that can fold up and then expand — like solar panels and antennas that are compact while they’re launched, but big and sturdy once they get out into space. A perfect job for origami.

Folding solar panels have been around for a while, but newer, more advanced materials are being used to make thinner panels. And with thinner panels, engineers are hoping to use all kinds of new folding techniques to fold the panels up even smaller. Some of these folds, like the Miura-ori fold, have already had their first tests in space. This fold uses alternating mountain and valley folds in a pattern that lets you open an entire sheet of paper by only pulling on two corners.

But of course the search for better folds is still going. In 2014, engineers from NASA’s Jet Propulsion Laboratory worked with origami experts to design prototypes for solar arrays that could easily unfold from compact cylinders into large flat disks. The cylinder would basically wrap around a spacecraft like a skirt, and use the spacecraft’s rotation to itself.

Folding techniques can also help you get things into spaces as cramped as the inside of your body. And in May 2016, researchers at MIT’s Computer Science and Artificial Intelligence Laboratory demonstrated a prototype robot that could be folded into a capsule, swallowed, and unfold inside your stomach. It would mainly be used to dislodge foreign objects from the stomach wall — say, if a kid swallows a button battery.

Batteries can burn a hole through tissue if you leave them there, so the robot could help doctors avoid risky surgery. The robot’s body is made of a folded-up sheet of pig intestine to protect it from the stomach’s acidic environment, with a magnet embedded in it. The researchers can manipulate magnetic fields outside of the body to move the robot along the walls of the stomach.

So far, they’ve demonstrated that their robot can safely remove objects from a pig stomach that was not currently inside a pig, and they want to test it on live animals next. And eventually, they’re hoping to redesign the robot so it can move around without those outside magnetic fields.

Origami is being used in other new robots, too. Researchers at Harvard have been experimenting with using an origami technique called snapology, which is a way of connecting a bunch of sheets of folded material into geometric shapes. The technique is similar the map-folding Miura-ori fold being used with those solar panels I talked about earlier, but instead of a single sheet of paper, several layers are stacked together. In March 2016, they built a cube-shaped robot out of smaller cubes to demonstrate the concept.

Using pressurized gas, the researchers could manipulate each fold in the whole block of cubes independently, which allowed them to expand and collapse the robot into all kinds of different shapes and sizes — including completely flat. And the same technique could eventually be used to fold and construct structural materials — to make temporary shelters, for example.

So far, we’ve talked about things that use motors, magnetism, and air pressure to fold. But the award for creativity in folding mechanisms should probably go to a group of researchers at North Carolina State University. In a paper published in March of this year in the journal Science Advances, the team announced that they’d figured out a way to make folds in a specific order by using colored lights. They printed different types of colored lines on a white sheet of plastic, then shined different colors of bright light on the plastic.

The light is reflected by most of the white plastic, but it’s absorbed along those colored lines. A red line, for example, will absorb colors that aren’t red, and a black line will absorb all the colors. When a line absorbs light, it gets warmer, which makes the colored plastic contract, turning the line into a hinge.

These hinges are printed in specific colors, so you can make the plastic fold in different ways by shining different colors of light on it. Extra-complicated folding patterns often need to be folded in a specific order, so scientists could use this system to design all kinds of new shapes and functions.

Another advantage of origami is that paper is cheap. That makes it especially useful for work in remote areas where people might need lightweight and biodegradable instruments. So a team of researchers at Binghamton University in New York has been developing folding paper batteries, powered by bacteria. And in 2016, they came up with a way to make them out of a single sheet of paper.

This type of battery is called a microbial fuel cell, and it works because as they turn food into energy, most bacteria move electrons through a series of chemical reactions called the electron transport chain. At the end of this process, they eject an electron, which is usually absorbed by an oxygen molecule. But if you remove the oxygen by drawing the bacteria into the center of the battery, that electron can be captured by something else... like one of the battery’s electrodes.

So the paper is designed to fold in a way that keeps the bacteria isolated, and separates the battery’s electrodes. It only provides a few microwatts of electricity, but even that tiny amount could be used for small-scale experiments or medical tests in places that don’t have access to electricity. Almost any drop of dirty water could power this battery, since it works with most bacteria. And since paper is biodegradable, it’s also easier to dispose of than traditional batteries.

Other kinds of paper equipment are being developed, too. In 2016, a team from Stanford built a paper centrifuge inspired by those whirligig toys, where you pull a string to spin a small disk really fast.

Centrifuges also work by spinning really fast, which lets them use centripetal force to separate things with different densities. One of their most useful applications is separating plasma from blood — a crucial step for a lot of of blood tests. A typical laboratory centrifuge costs around $700 and weighs more than 2 kilograms, which means a lot of people in developing countries, especially in remote areas, don’t have access to one.

But this paper centrifuge costs only 70 cents and weighs just 2 grams, and it gets similar results. The team showed that it can be used to diagnose conditions like malaria and sleeping sickness, and the next step is to actually test it in a clinical setting.

So from outer space to your stomach, things that fold, compress, and expand are becoming an important part of the future of science. And who knows? Maybe someday you’ll have to take an origami class as part of your engineering degree.

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