Fibers are usually tough or strong; they normally can't be both. Now, materials engineers have developed a structural nanofiber that is both tough and strong. Their new material could potentially transform everything from airplanes and bridges to body armor and bicycles.

So why can't materials be tough and strong? Think of a ceramic plate; it's strong because it can carry dinner to the table, but lacks toughness since it will shatter when it's dropped. Strength refers to a material's ability to carry a load, while toughness refers to the amount of energy needed to actually break it. In the world of materials, the two attributes are usually mutually exclusive.

This new nanofiber, though, actually solves the dilemma of sacrificing strength for toughness and vice versa. It's an exceptionally thin plyacrilonitrile nanofiber, which is a type of synthetic polymer related to acrylic. The researchers developed it using a technique called electrospinning, which involves applying high voltage to a polymer solution until a small jet of liquid ejects, resulting in a continuous length of nanofiber. By making this fiber thinner than ever before, the researchers were not only able to increase its strength, but were also able to increase its toughness.

"Our discovery adds a new material class to the very select current family of materials with demonstrated high strength and toughness," said the research team's leader, Yuris Dzenis, in a news release. "If structural materials were tougher, one could make products more lightweight and still be very safe."

The scientists have a theory about why exactly the new material is both tough and strong. It's possible that the toughness comes from the nanofibers' low crystallinity. In other words, it has many areas that are structurally unorganized. These amorphous regions allow the molecular chains to slip around more and, in consequence, give them the ability to absorb more energy.

In fact, this unique property could allow researchers to create body armor that's far lighter. Bulletproof vests require materials that are both tough and strong. This new material could potentially replace current materials in the vests.

The details of this new material are published in the journal ACS Nano.