Microscale knots double tensile strength of new material

Knots are known to add strength to materials, the slightest twists of DNA to (potentially) the very fabric of the universe. Now Caltech engineers have developed a new material made up of microscopic-scale knots and shown to be much stronger than a version of the material made of the same material without knots.

The material is made up of polymers arranged in a series of single knots, with an added twist to absorb more energy. However, the fibers are not physically tied to these nodes. Instead, they are 3D printed in this shape, which is easier to produce and prevents them from falling apart. Each knot is approximately 70 micrometers high and wide, making it the first time a material has had knots of this magnitude.

The gnarled material was then subjected to strength testing, where it was stretched to breaking point. This was compared to a version of the material made of the same material but with an interwoven structure instead of being knotted. And sure enough, the knots allowed the material to absorb 92% more energy and sustain more than twice the amount of stress before it broke, than the other architecture.

An animated comparison of the tensile strength of a new material, consisting of a knotted form (left) and an interlaced form (right)


The team says the durability and deformability of these types of knotted materials could eventually make them useful for biomedical and aerospace applications. In future work, the researchers plan to study materials made with more complex nodes.

“The ability to overcome the general trade-off between material deformability and tensile toughness [the ability to be stretched without breaking] offers new ways to design devices that are extremely flexible, durable and can operate in extreme conditions,” said Widianto P. Moestopo, lead author of the study.

The research was published in the journal Scientists progress.

Source: Caltech

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