Nature’s armour: A lobster tale

Biological structures may provide insight to prevent and treat sports-related injuries.

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

Breanne Grady, USC Viterbi School of Engineering August 25, 2017

According to a study published this July in the Journal of the American Medical Association, chronic traumatic encephalopathy (CTE) was found in 99% of deceased NFL players’ brains donated to scientific research.

CTE results from taking repeated blows to the head, par for the course in contact sports like football and boxing, and is associated with memory disturbance, behavioral and personality changes, Parkinson’s Disease, and speech and gait abnormalities.

The good news: a team of USC Viterbi engineers might aid in future CTE prevention and treat other sports injuries with 3-D printed body armour like helmets, other protective devices and prosthetics – all by learning from nature’s toughest structures.

Learning From Lobsters
USC Viterbi post-doctoral scholar Yang Yang first came to the idea while eating lobster in a restaurant and having difficulty breaking the lobster’s claws to get to the meat.

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

Indeed there was.

As it turns out, former research has found that lobsters as well as fellow sea-dwellers, mantis shrimps, have an especially strong design to their outer shells made up of chitin, a fibrous material. This design, called Bouligand-type fiber alignment, means that structural fibers align in a spiral and are constantly rotating, making it difficult for small cracks to expand into larger cracks.

“The crack has to rotate with the fibers, so you get a much longer cracking propagation path,” said Yong Chen, a USC associate professor of Industrial and Systems Engineering. “You may have a micro-crack, but it doesn’t break the shell.”

Brilliant By Design
Chen, an expert in 3-D printing, also supervises Yang and together they have developed an electric-assisted 3-D printing process that aligns layers of material in bio-inspired and physically resilient ways like Bouligand-type alignment. They are the first to integrate an electrical field into 3-D printing.

Their study involved 3-D printing small prototypes of the human meniscus in the knee, essentially cartilage that acts as a shock absorber between the thighbone and shinbone and is vulnerable to sports-related injury. This year, the research team made the cover of the March 2017 issue of Advanced Materials for their innovation.

Electrically-assisted 3D printing can create materials with stronger high-impact resistance. Yong Chen photo

In the experiment, the team tested the impact resistance of a plastic model, a model made of plastic and carbon nanotubes – a type of fiber, and one made of plastic and carbon nanotubes with an electric field applied during the printing process to align the fibers within.

“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,” said Chen. “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.”

Brave New Armour
Next steps for the research include building bigger prototypes and making them biocompatible.

“For clinical applications like a prosthetic meniscus, the material needs to be biocompatible, so we need to find the perfect material, perhaps hydrogel,” Yang said.

“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,” Chen said. “The electrically assisted 3-D printing provides a new tool to fabricate arbitrary 3-D geometries with any nanofiber orientations. In addition to the reinforced structures, we believe this manufacturing capability offers tremendous possibilities for applications in aerospace, mechanical, and tissue engineering.”

In the future, this could mean that a football player has their head scanned, and using a digital design of their own unique head shape, a customized, super-strength helmet is 3-D printed on the spot. For a prosthetic meniscus, a person’s knee could be scanned to print a replacement with the appropriate dimensions.

In other words, we could be looking toward a brave new world of personalized protection. Thanks, in part, to lobsters.

For their research paper, Chen and Yang worked with co-authors Kirk Shung and Qifa Zhou, both professors in the USC Viterbi Department of Biomedical Engineering.

Biomimetic Anisotropic Reinforcement Architectures by Electrically Assisted Nanocomposite 3D Printing, Yang Y, Chen Z, Song X, Zhang Z, Zhang J, Shung KK, Zhou Q, Chen Y. Adv Mater. 2017 Mar;29(11). doi: 10.1002/adma.201605750. Epub 2017 Feb 10.

Protection mechanisms of the iron-plated armor of a deep-sea hydrothermal vent gastropod, Haimin Yao, Ming Dao, Timothy Imholt, Jamie Huang, Kevin Wheeler, Alejandro Bonilla, Subra Suresh, and Christine Ortiza, Proc Natl Acad Sci USA. 2010 Jan 19; 107(3): 987–992. doi: 10.1073/pnas.0912988107

Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football, Mez J, Daneshvar DH, Kiernan PT, Abdolmohammadi B, Alvarez VE, Huber BR, Alosco M1, Solomon TM, Nowinski CJ, McHale L, Cormier KA, Kubilus CA, Martin BM, Murphy L, Baugh CM, Montenigro PH, Chaisson CE, Tripodis Y10, Kowall NW, Weuve J, McClean MD, Cantu RC, Goldstein LE, Katz DI, Stern RA, Stein TD, McKee AC. AMA. 2017 Jul 25;318(4):360-370. doi: 10.1001/jama.2017.8334.

Source Unversity of Southern California, Viterbi School of Engineering

Secrets of the conch shell and its toughness. The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in its toughness: the conch. Now, researchers at MIT have shown that the conch shell’s superior strength can be reproduced in engineered materials. Massachusetts Institute of Technology (MIT). Published on Youtube May 26, 2017.

The research was supported by the Office of Naval Research, a National Defense Science and Engineering Graduate Fellowship, the Defense University Research Instrumentation Program (DURIP), the Institute for Soldier Nanotechnologies (ISN), and the Natural Sciences and Engineering Research Council of Canada.

Also see
Conch shells spill the secret to their toughness in MIT News
Making Stronger Protective Gear: Researchers Replicate Biological Structure of Lobster Claws Using Electric-Assisted 3D Printing Process in 3Dprint.com
Increased helmet use in alpine sports fails to reduce risk of traumatic brain injury in Medical Xpress

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