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[Image: Boston University Center for the Study of Traumatic Encephalopathy]

A study published in the Journal of the American Medical Association last month found that chronic traumatic encephalopathy (CTE), which results from repeated blows to the head, was found in 99% of the brains of deceased NFL players that had been donated for scientific research. Multiple hits to the head are common for those who play contact sports, like boxing and football, and CTE is associated with issues like speech and gait abnormalities, memory disturbance, behavioral and personality changes, and even Parkinson’s Disease. Unfortunately, there’s not a cure, as the progressive degenerative disease can only definitively be diagnosed postmortem. But a team of engineers from USC Viterbi School of Engineering are studying biological structures to see if 3D printing technology can be used to prevent sports-related injuries, and CTE.

This question has been asked before, and as a result, we’ve seen all kinds of 3D printed sports safety equipment, like helmets, mouthguardsshin guards, and even a binding system for snowboards. The USC Viterbi team is studying a specific sea creature to see if it’s possible to make stronger 3D printed body armor…and no, it’s not fish.

Yang Yang, a post-doctoral scholar at USC Viterbi, was enjoying a lobster dinner in a restaurant, but having a difficult time breaking the crustacean’s claws to get to the meat inside.

Yang said, “I thought maybe there was some special structure involved that brings the lobster claws very high impact resistance.”

Lobsters and other crustaceans have exoskeletons with extraordinarily high impact resistance that has been studied for manufacturing stronger materials. [Image: Wikimedia Commons]

He was right – earlier this summer, MIT researchers published a study about the extreme durability of the conch shell, and the possibility of using it to make human body armor. The outer shells of lobsters and mantis shrimps have a very strong design, made of fibrous chitin material, called Bouligand-type fiber alignment: the structural fibers in the design align in a spiral, and are rotating constantly, so small cracks have a hard time expanding into larger cracks that could break the shell.

[Image: USC Viterbi]

“The crack has to rotate with the fibers, so you get a much longer cracking propagation path. You may have a micro-crack, but it doesn’t break the shell,” explained Dr. Yong Chen, a 3D printing expert and USC Associate Professor of Industrial and Systems Engineering.

Dr. Chen and Yang worked together and developed a process that adds an electrical field into 3D printing. The electric-assisted 3D printing process aligns layers of material in resilient, bio-inspired ways, like a lobster shell’s design. The team, consisting of Yang, Zeyu Chen, Xuan Song, Zhuofeng Zhang, Jun Zhang, K. Kirk Shung, Qifa Zhou, and Dr. Chen, published a research paper on their work, titled “Biomimetic Anisotropic Reinforcement Architectures by Electrically Assisted Nanocomposite 3D Printing,” which made the cover of the March 2017 Issue of Advanced Materials.

The abstract reads, “Biomimetic architectures with Bouligand-type carbon nanotubes are fabricated by an electrically assisted 3D-printing method. The enhanced impact resistance is attributed to the energy dissipation by the rotating anisotropic layers. This approach is used to mimic the collagen-fiber alignment in the human meniscus to create a reinforced artificial meniscus with circumferentially and radially aligned carbon nanotubes.”

The team 3D printed prototypes of human meniscus in the knee, which absorbs shock between the thighbone and shinbone, and then tested the impact resistance of a model made with plastic, one made with plastic and carbon nanotubes, and a second model of plastic and carbon nanotubes, but with an electric field applied during printing to align the interior fibers.

Dr. Chen explained, “The carbon nanotube is a microscale fiber, so basically when you try to pull it, you have a lot of fiber inside, so it’s reinforced, over a thousand times stronger than plastic. When you just add nanofibers to plastic, overall you get 4x improvement in strength. And if we add and then align the same nanofibers with a 1000-volt electric field, you get 8x improvement in strength.”

The research team’s next move will be to build bigger, biocompatible prototypes; Yang says it’s imperative that they find the perfect material, as their research has clinical applications.

“Right now, we’re trying to improve this electric-assisted 3-D printing process with the help of an NSF grant started April 1, 2017. The electrically assisted 3-D printing provides a new tool to fabricate arbitrary 3-D geometries with any nanofiber orientations,” said Dr. Chen. “In addition to the reinforced structures, we believe this manufacturing capability offers tremendous possibilities for applications in aerospace, mechanical, and tissue engineering.”

Think about the possibilities: a football player has their head scanned, and then a custom, super-strong helmet is 3D printed for them right then and there, using a digital design of their unique head shape; the same concept would apply for a prosthetic meniscus for a player’s knee. There have been many 3D printing innovations inspired by nature, from a 3D printable ceramic foam ink and bio-friendly 3D printing materials to a 6-axis 3D printer and a better design for tandem wing airplanes…and to think, USC Viterbi’s lobster claw-inspired research came about after having a hard time cracking into a dinner entrée. Discuss in the Lobsters forum at 3DPB.com.

[Source: USC Viterbi]

 

 

 

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