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World's tightest knot could lead to materials breakthroughs

If you’ve ever had the experience of trying to undo a knot that’s way too tight, spare a moment’s thought for researchers at the U.K.’s University of Manchester — who just tied the tightest and smallest knot in the known universe.

With a total strand length of 192 atoms, the eight-crossing, 24-atom-per-crossing knot is tied in a molecular strand just half a nanometer wide. To put that in real-world terms, it’s a knot in a thread that’s a ten-thousandth the thickness of a single human hair.

“These knots are so small that it’s not possible to tie them manually like you would a shoelace,” David Leigh, professor of organic chemistry at the University of Manchester, told Digital Trends. “Instead, we use chemistry to get the knots to self-assemble. To do this, we mix together some organic building blocks and metal salts, consisting of iron ions and chloride ions. The metal ions are sticky in certain directions, which makes the organic building blocks adhere and twist around them in the way that we designed. Once that basic structure has been formed, we then add another catalyst, which fuses the ends of the strands and joins them together to form a closed loop.”

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Leigh said that it would theoretically be possible to create an even smaller knot in the future, but it’s not going to be easy. “It won’t be possible to go much smaller than this because the bonds between the atoms would simply break apart,” he explained.

While this work may seem like a nerdy lab contest, Leigh noted that nanoscale research such as this does have practical applications in much the same way that knotting does at the macroscale.

“Knotting and weaving have always led to new technologies — from prehistoric man onward,” he continued. “Being able to tie knots let man make fishing nets, tie axes onto handles, and weave fabrics to protect himself from the cold. There’s no reason to believe that knotting at the molecular level won’t prove just as important when it comes to creating advantageous properties in materials.”

In particular, he said that weaving molecular strands could allow for the creation of new materials that will be stronger, lighter, and more flexible than their non-woven counterparts.

That remains a hypothetical for now, though. As Leigh told us, “Just because I can tie a knot doesn’t mean that I can knit a Christmas jumper.”