Massachusetts Institute of Technology and bony 3D printing

Markus Buehler (last mentioned here in a Nov. 28, 2012 posting*, about spider silk and music) and his research team at the Massachusetts Institute of Technology (MIT) have been inspired by various biomaterials to create materials that resemble bone matter, from the June 17, 2013 news item on ScienceDaily,

Researchers working to design new materials that are durable, lightweight and environmentally sustainable are increasingly looking to natural composites, such as bone, for inspiration: Bone is strong and tough because its two constituent materials, soft collagen protein and stiff hydroxyapatite mineral, are arranged in complex hierarchical patterns that change at every scale of the composite, from the micro up to the macro.

Now researchers at MIT have developed an approach that allows them to turn their designs into reality. In just a few hours, they can move directly from a multiscale computer model of a synthetic material to the creation of physical samples.

In a paper published online June 17 in Advanced Functional Materials, associate professor Markus Buehler of the Department of Civil and Environmental Engineering and co-authors describe their approach.

The June 17, 2013 MIT news release by Denise Brehm, which originated the news item, explains the researchers’ approach in more detail (Note: A link has been removed),

The collagen in bone is too soft and stretchy to serve as a structural material, and the mineral hydroxyapatite is brittle and prone to fracturing. Yet when the two combine, they form a remarkable composite capable of providing skeletal support for the human body. The hierarchical patterns help bone withstand fracturing by dissipating energy and distributing damage over a larger area, rather than letting the material fail at a single point.

“The geometric patterns we used in the synthetic materials are based on those seen in natural materials like bone or nacre, but also include new designs that do not exist in nature,” says Buehler, who has done extensive research on the molecular structure and fracture behavior of biomaterials. His co-authors are graduate students Leon Dimas and Graham Bratzel, and Ido Eylon of the 3-D printer manufacturer Stratasys. “As engineers we are no longer limited to the natural patterns. We can design our own, which may perform even better than the ones that already exist.”

The researchers created three synthetic composite materials, each of which is one-eighth inch thick and about 5-by-7 inches in size. The first sample simulates the mechanical properties of bone and nacre (also known as mother of pearl). This synthetic has a microscopic pattern that looks like a staggered brick-and-mortar wall: A soft black polymer works as the mortar, and a stiff blue polymer forms the bricks. Another composite simulates the mineral calcite, with an inverted brick-and-mortar pattern featuring soft bricks enclosed in stiff polymer cells. The third composite has a diamond pattern resembling snakeskin. This one was tailored specifically to improve upon one aspect of bone’s ability to shift and spread damage.

The scientists are hinting that they’ve improved on nature and that may be so but I recall reading similar suggestions in studies I’ve read about 19th and 20th century research. It seems to me that scientists have claimed to be improving on nature for quite some time.

Interestingly, the suggested application for this new material is not biomedical, from the news release,

According to Buehler, the process could be scaled up to provide a cost-effective means of manufacturing materials that consist of two or more constituents, arranged in patterns of any variation imaginable and tailored for specific functions in different parts of a structure. He hopes that eventually entire buildings might be printed with optimized materials that incorporate electrical circuits, plumbing and energy harvesting. “The possibilities seem endless, as we are just beginning to push the limits of the kind of geometric features and material combinations we can print,” Buehler says.

You can find a link to and a citation for the published paper at the end of the ScienceDaily June 17, 2013 news item.

* Date changed from 2013 to 2012 on June 4, 2014

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