Material science advancement after tightest knot created

Scientists at the University of Manchester have created the tightest knot ever achieved, opening up a potential avenue for a new generation of advanced materials.

This method of braiding multiple molecular strands has enabled eight crossings in a 192 atom closed loop about 20nm long. By creating different types of molecular knots the scientists are able to examine how knotting affects the strength and elasticity of materials.

Professor David Leigh, from the University of Manchester who led the research, said: “We ‘tied’ the molecular knot using a technique called ‘self-assembly’, in which molecular strands are woven around metal ions, forming crossing points in the right places just like in knitting - and the ends of the strands were then fused together by a chemical catalyst to close the loop and form the complete knot.”

These interweaving polymer strands could possibly create materials that are tougher, lighter and more flexible, similar to woven threads. Kevlar, one of the strongest man-made polymers is used for bulletproof vests and body armour. It is composed of rigid molecules aligned in a parallel structure.

Professor Leigh said, “Some polymers, such as spider silk, can be twice as strong as steel so braiding polymer strands may lead to new generations of light, super-strong and flexible materials for fabrication and construction.”

The research was published in Science.