Knots are known for boosting the strength of materials, from the tiniest twists of DNA to (potentially) the very fabric of the universe. Now, Caltech engineers have developed a new material consisting of microscale knots, and shown that it’s far tougher than a version of the material made of the same stuff without knots.
The material is made of polymers arranged in a series of basic overhand knots, with an extra twist to absorb more energy. The fibers aren’t physically tied into these knots, however – instead, they’re 3D-printed into that shape, which is simpler to produce and keeps them from coming undone. Each knot measures about 70 micrometers high and wide, making this the first time a material has been composed of knots of this scale.
The knotty material was then subjected to stress tests, where it was stretched to breaking point. This was compared to a version of the material made of the same stuff but with an interwoven structure instead of knotted. And sure enough, the knots allowed the material to absorb 92% more energy and sustain more than twice the amount of strain before it snapped, than the other architecture.
The team says that the durability and deformability of these kinds of knotted materials could eventually make them useful for biomedicine and aerospace applications. In future work, the researchers plan to investigate materials made with more complex knots.
“The capability 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 Science Advances.
Source: Caltech