Take a piece of raw bacon. Uncooked, a strip of bacon will lie flat, but drop it into a sizzling frying pan and it will start to curl. Bacon curls because the fat melts away and shrinks at a different rate than the muscle tissue. Theoretically, that means if you could 3-D print a strip with exactly the right configuration of fat to muscle, you could program a piece of bacon that would curl up in the pan in any shape you wanted.
That's what researcher Skylar Tibbits and his team at MIT's Self-Assembly Lab (made up of Athina Papadopoulou, Carrie McKnelly, Christopher Martin, and Filipe Camposare) are trying to do. No, they haven't figured out how to program bacon. Not yet, anyway. A year after they figured out how to program plastic as a proof-of-concept on how to make make materials that assemble themselves, the Self-Assembly Lab is back, and they have come up with a way to program wood, carbon fiber, and fabric in such a way that could make everything from just-add-water, self-constructing Ikea furniture to power-lacing Back to the Future Air McFlys a reality.
Every ninth-grade physics student knows that most materials change when exposed to energy. Water freezes into ice. Wood swells when exposed to moisture. Plastic melts when you heat it up. And so on. What MIT's Self-Assembly Lab tries to do is figure out ways these changes can be precisely controlled, so that a material shrinks, expands, and curls in a repeatable way. They do this by marbling the materials they want to program with another material that doesn't react to energy in the same way. It's basically a skeleton flowing through a 3-D printed object: something with joints that allows a sheet of unbroken material to precisely bend, flex, expand, and contrast according to logic designed into that material from the start.
"What we're really trying to make is robots without robots," Tibbits tells me when I visit the lab this week. "We want to design materials that can transform themselves when exposed to energy, but which don't necessarily require circuit boards, electronics, or other moving parts to operate." Tibbits and his team call this technique 4-D printing—the extra "D" stands for the ability of 3-D printed materials to be dynamic in the way they change shape—and it has many possible applications.
For example, in wood. Sitting on a desk outside of Tibbits's MIT office is an Eames Plywood Elephant. Designed by Charles and Ray Eames in 1945, the Eames Elephant was originally meant to be made in molded plywood, but never entered mass production. Why not? Because molding plywood is expensive in both man hours and energy expenditure. In the end, the Eames felt that the Plywood Elephant could simply never be manufactured at a price that made the design appropriate for children. It wasn't until 2010 that the Eames Elephant entered mass production at an affordable price. And even then, it was only quasi-affordable because it was made of plastic.
But using programmable wood, the Eames Elephant could become the affordable wooden toy it was designed to be. Next to an Eames Elephant at the Self-Assembly Lab is the head of a much tinier doppelgänger, 4-D printed out of wood composite using one of MIT's machines. By controlling the pattern of the wood grain, Athina Papadopoulou, a researcher at the Self-Assembly Lab, was able to 4-D print a flattened wooden elephant that sprang into its proper shape as it dried. And this technique can be used for more than making designer elephants. Working with product designer, Christophe Guberan, the team is now developing a series of product concepts around programmable wood.
Imagine flat-pack furniture that, like a magic grow capsule, you just add water to construct. Tibbits says that his team is already in discussions with one furniture company (which he declined to name) about these sorts of possibilities.
Wood is just one of the programmable materials Tibbits and his team have mastered. Another is fabric. Like wood, fabric that can be shipped flat and spring into shape when it reaches its destination has fascinating possibilities for the furniture industry. But it could also be used in the clothing and sneaker industries.
Remember Back to the Future II's self-lacing McFlys? The reason Nike won't actually make them a reality is because right now sneakers that can lace themselves up would require an embedded mechanical system that would likely break down in something as high-impact as a basketball sneaker. But using programmable materials, Tibbits and his team says they can make self-lacing McFlys a reality, simply by designing laces that can tighten or loosen on their own. This could conceivably be done using any power source, from heat generated by a person's foot to electricity provided by a simple battery. (Don't get too jazzed yet, though: Tibbits is still just spitballing about self-lacing McFlys. But when he actually makes a pair, we'll be the first to report it.)
"The more complicated something is, the more likely it is to break," Tibbits says. "That's especially true with moving components like sensors, electronics, and gears. But that's the advantage of programmable materials. It's a moving component made out of a single material, which not only makes it less likely to fail, but also reduces weight."
That's why the programmable material you're most likely to see first in the real world is carbon fiber. Teaming with Carbitex, a maker of flexible carbon fiber materials, the Self-Assembly Labs have figured out how to 4-D print light, super-strong carbon fiber sheets in such a way that they curl and flatten in response to heat. That makes programmable carbon fiber a perfect material for industries where there's an emphasis on strength, lightness, and reliability, like automobiles or aerospace. In fact, MIT is already working on helping Airbus develop a transformable, carbon fiber component for regulating heat and air intake in their plane engines. They're also helping Briggs create a spoiler for the Mono, which they hope will help make that car the fastest street legal car in America.
Between testing and government approval, we're still a few years away from riding in road-ready racecars and regulation-approved airplanes that depend on programmable materials. But what MIT has proven is that 3-D (or 4-D) printing isn't just about replication. It's about turning the dumbest objects around us into transformers. And maybe that's the way 3-D printing will really change the world. After all, once you understand how to program matter, materials are only as dumb as you let them be.