Record knot could unravel techniques for new materials

192-atom long structure woven “just like knitting.”

12th January 2017
The X-ray crystal structure of a 192-atom-loop © Robert W. McGregor

The X-ray crystal structure of a 192-atom-loop © Robert W. McGregor

A team of chemists from the University of Manchester have created the world’s tightest knot. Their contorted construction crosses itself eight times, in spite of the fact it is only 192 atoms long.

“We used a technique called self-assembly,” says lead researcher Prof David Leigh. “Molecular strands are woven around metal ions, forming crossing points in the right places – just like in knitting”.

They then used a chemical catalyst to fuse the ends of the tiny loop to complete the knot. “The tightness of a knot can be measured as the distance between strand crossings, so that’s just 24 atoms per crossing, or about 0.3 nanometers – very tight indeed!”

If you’ve ever spent hours untangling the cables behind the TV you might wonder why they even bothered. “These molecular techniques should also be applicable to weaving,” says Leigh. “Kevlar consists of rigid molecular rods aligned in parallel, but interwoven polymers could create much tougher, lighter and more flexible materials. Some polymers, such as spider silk, can be twice as strong as steel.”

By tying different knots researchers can explore how knotting effects produce useful properties in the finished materials.

The results are published in the journal Science.


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