Tough, fish scale-like material with soft flexibility could protect soldiers, astronauts

A paper outlining the characteristics, test results and applications of the new material was published in a recent issue of the technology journal Soft Matter, a publication of the Royal Society of Chemistry. The research was led by Assistant Professor Stephen Rudykh, head of the Technion's Mechanics of Soft Materials Laboratory.

"Many species of fish are flexible, but they are also protected by hard scales," said Prof. Rudykh. "Taking inspiration from nature, we tried to replicate this protecto-flexibility by combining two layers of materials -- one soft for flexibility and the other with armor-like scales. The secret behind this material is in the combination and design of hard scales above with soft, flexible tissue below."

Generally, strength and flexibility are competing properties, explained Professor Rudykh. You can't have both. However, the research team found a way to increase the penetration resistance by a factor of 40, while the flexibility of the soft material was reduced by only a factor of five. If the application is, for example, a military uniform for combat, more flexibility can be built into the areas needing flexibility, such as the elbows and knees, while the anti-penetration properties elsewhere, such as in the upper body, can be beefed-up.

"That attribute allows for the fabric to be tailored to the wearer's body and the environment that the wearer will be facing," explained Professor Rudykh, who carried out post-doctoral studies at MIT where he worked with 3-D printing technology before joining the Technion. "This work is part of a revolution in materials properties. Once we can gain control over a material's micro properties, using 3-D printing we can create materials of an entirely different type, each with the ability to be adjusted to fit the wearer, the need, and the environment."

The researchers have conducted initial testing on the material and are moving into dynamic tests using fast-moving projectiles, both bullets and small particles, and also testing the flexibility attribute under pressure.

"Our findings provide new guidelines for developing simple material architectures that retain flexibility while offering protection with highly tunable properties," concluded the researchers. "The tailored performance of the protective system -- with characteristics that can be tuned according to the required movements at different regions of the body -- draws its abilities from the microstructural geometry. The ability for a given microstructure to offer different deformation resistance mechanisms is key to achieving the multifunctional design of stiff plates and soft matrix. We found that careful selection of microstructural characteristics can provide designs optimized for protection against penetration while preserving flexibility."