What do a clove hitch, a sheet bend and a sheepshank all have in common? They are of course, as any former scout will tell you, all knots. But I bet they couldn’t tie an 819 knot: at less than a millionth of a millimetre across, it’s the world’s smallest knot and has been tied by a team at the University of Manchester. They made the molecular tangle in a test tube using a sequence of carefully-controlled chemical reactions that used iron catalysts to bend and entwine short strings of carbon-rich molecules. I heard how from lead author David Leigh…

• The knot is 192 atoms long with eight crossings and is the smallest, tightest knot ever tied.
• The width of the knot is half a nanometre – less than one millionth of a millimetre or ten thousand times thinner than a human hair.
• In mathematics, a knot describes a closed loop, which means that the knot here with its ends fused together, is still by definition a knot.
• By viewing the positions of the atoms using X-ray crystallography, the knot can be seen to look like a four-leaf clover with extra strands wrapping around the outside of the leaves to generate the 8 crossings.
• The knot is made using the technique of self-assembly where molecular strands are woven around metal ions, not too dissimilar to knitting.
• The new technique used to make the knot could lead to a method of weaving molecular strands together to form stronger, lighter and more flexible materials.
• In particular, Kevlar vest could be made much stronger by weaving the ‘rods’ of material together, rather than having them packed closely together like pencils in a pencil box, as is currently the case.

You can listen to the full interview for the Naked Scientists here.