Knots are extremely useful in everyday life, even at the nanoscale level. Now, researchers from the University of Manchester have just created the first three-strand molecular braid.
The team, led by Professor David Leigh, have developed a technique that uses iron ions to carefully direct and braid 192 atoms that intersect at eight distinct points. The breakthrough, published this week in Science, represents the most complex knot synthesized in a lab so far.
“The eight-crossings molecular knot is the most complex regular woven molecule yet made by scientists,” Professor Leigh said in a statement. “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."
Molecular knots are common in nature. Polymer chains can often form them, and even circular DNA and about 1 percent of known proteins show knotted structures. There are more than 6 billion known molecular knots possible and so far only three nontrivial knot topologies have been made by scientists.
“Tying knots is a similar process to weaving so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands,” Leigh added.
The ability to weave complex molecules together can open the door to many applications for nano-knotted materials, from textiles to electronics.
“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,” continued Leigh. “For example, bullet-proof vests and body armour are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure – however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world.”
This technology has potential applications in the production of many different types of knots and might soon be in a breakthrough material near you.