Summary:

Eventually, their technique could be applied to print bones for medical use, plane components and even buildings.

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When a bone breaks, it hurts; but it could be a lot worse. Bones are actually quite adept at spreading strain over a wide area, minimizing damage.

MIT researchers emulated this unique property to develop a highly fracture-resistant material that can be made with a 3D printer. They published their results Monday in Advanced Functional Materials (subscription required).

Bones are made of collagen and a mineral — soft and brittle materials, respectively. But combine the two into a bone and they become much stronger. The mineral provides structure while collagen distributes energy over a larger area.

The two interlock in complicated ways, so first the researchers modeled a bone on a computer. Software translated this into a design readable by a Stratasys 3D printer capable of printing with two materials. Within hours, the researchers had their synthetic bone. The 3D printer produced a sheet of polymer about half the size of a piece of paper and one-eighth inch thick. Hard polymer formed the hard bricks of mineral while soft polymer worked as flexible collagen mortar. The material was as tough as bone and more than 20 times stronger than printed polymers that resembled just collagen or mineral, the paper said.

The 3D-printed bone-like material resembles a brick wall. Here it is shown against a mollusc's nacre-covered inside.

The bone-like material resembles a brick wall. Here it is shown against a mollusc’s nacre-covered inside. Graham Bratzel/MIT

“The combination of exciting results from earlier computational investigations and the advancement of 3D printing technology was the basis to this work,” said MIT associate professor Markus Buehler, who co-authored the paper. “We realized that we could manufacture composite materials with great mechanical properties through a relatively simple design process, and this was immediately appealing.”

Buehler said the bone-like material could eventually be used as a lightweight option for automotive and aerospace engineering or to build an actual artificial bone for medical purposes. The design and printing process could also be applied to other natural items, and even new, never-before-seen materials. The polymers are light and inexpensive, and can be scaled up to produce large structures like buildings.

“As of now 3D printing is not a scalable process – printers are typically confined in the volume of parts they can print and we are not aware of practical methods to combine separate parts printed in different printers,” Buehler said. “Increased attention around 3D printing and more studies such as ours, showing that 3D printing is useful for more than just prototyping, will likely motivate the industry to become more scalable.”

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