It’s made using keratin extracted from recycled wool. Keratin is a fibrous protein that’s found in hair, which, of course, has a habit of returning to its natural form.

The researchers shaped a single chain of keratin into a spring-like structure. They twisted two of those together and used many such “coiled coils” to assemble large fibers. When a stimulus is applied to the material or it’s stretched out, those structures uncoil and the bonds realign. The material stays that way until it’s triggered to return to its original state, which is programmed with a solution of hydrogen peroxide and monosodium phosphate.

In one test, researchers programmed a sheet of keratin to have an origami star as its permanent shape. They dunked the sheet in water to make it malleable and rolled it into a tube. But when the team put that tube in the water again, it unrolled and reformed as the origami star.

The researchers believe the material could help reduce waste in the fashion industry. They suggested it could be used for truly one-size-fits-all clothing that stretches to fit the wearer, or bras “whose cup size and shape can be customized every day.” Consumers could save as well if they don’t have to replace stretched-out clothes quite so often.

“This two-step process of 3D printing the material and then setting its permanent shapes allows for the fabrication of really complex shapes with structural features down to the micron level,” Luca Cera, a SEAS postdoctoral fellow and first author of a paper on the material, said in a press release. “This makes the material suitable for a vast range of applications from textile to tissue engineering.”

“Bone is a building,” says Purdue University professor Pablo Zavattieri. “It has these columns that carry most of the load and beams connecting the columns. We can learn from these materials to create more robust 3D-printed materials for buildings and other structures.”

The researchers discovered that the “beams” in bones provide more stiffness and strength than previously understood. Those beams, also known as trabeculae, form vertical plate-like struts and horizontal rod-like struts in bone. In a study published in Proceedings of the National Academy of Sciences, they propose that it’s the horizontal struts that increase the fatigue life of bone.

They believe that 3D-printed building materials designed with similar internal structures might lead to more durable buildings. To test the theory, Zavattieri’s lab designed 3D-printed polymers with architectures similar to trabecula.

Mechanical analysis simulations found that the thicker the horizontal struts, the longer the polymer lasted under load. Because thickening the struts didn’t significantly increase the mass of the polymer, the team believes similar bone-inspired polymers could be used to create resilient, lightweight building materials, and those could be key to creating 3D-printed homes and buildings.

The researchers had actually been experimenting with ways to grow CNTs on electrically conductive materials — such as aluminium — to boost their electrical and thermal properties. The color of the resulting material surprised the team, and they only realized what they had invented after they measured its optical reflectance.

The discovery is currently being showcased at an art exhibit titled “The Redemption of Vanity” at the New York Stock Exchange, where a 16.78-carat natural yellow diamond has been coated in the material. Instead of a brilliant, sparkling gem, the stone — which is worth an eye-watering $2 million — appears as a flat, black void.

However, the team says the material has practical applications, too. According to Brian Wardle, professor of aeronautics and astronautics at MIT, it could be used in optical blinders that reduce unwanted glare, to help space telescopes spot orbiting exoplanets. And, he says, the material could get even blacker still.

“There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance,” Wardle says. “Our material is 10 times blacker than anything that’s ever been reported, but I think the blackest black is a constantly moving target. Someone will find a blacker material, and eventually we’ll understand all the underlying mechanisms, and will be able to properly engineer the ultimate black.”

The 3D-printed hydrogel is a dual polymer that’s capable of bending, twisting or sticking together when treated with certain chemicals. One polymer has covalent bonds, which provide strength and structural integrity. The other polymer has ionic bonds, which allow more dynamic behaviors like bending and self-adhesion. Together, the polymers create a material that is soft, strong and responsive — ideal for creating a soft, robotic grip.

Above, the researchers demonstrated the self-adhering behavior on the tail of a 3-D printed hydrogel salamander.

The hydrogel could also be a promising base for microfluidic devices — used for everything from cancer treatments to liquid-based watch tech and detecting explosives. Until now, it’s been hard to pattern hydrogels with the complex channels and chambers needed in microfluidics. But because this new material is 3D-printed, it can be made in stackable LEGO-like blocks, and “complex microfluidic architectures” can be incorporated into each block. These could create a type of modular system in which blocks with different microfluidic channels could be fit together as needed.

The material isn’t quite ready for use. Researchers say they’re still tweaking the polymers to get even more durability and functionality. If they succeed, this could make building soft robotic components and labs-on-a-chip as simple as snapping together LEGO pieces — or at least significantly easier.

Above, the self-adhering behavior was used to make hydrogel building blocks that fit together like LEGO blocks.