Trying to knot tiny molecules together is a task that is exactly as difficult as it sounds. However, manipulating molecules into ever tighter knots is a goal that many researchers eagerly pursue, and not just for the daunting challenge it provides. Scientists believe that making different types of molecular knots can be used as a method to probe how knotting affects strength and elasticity of materials. This, in turn, can lead to the creation of polymer strands that can be used to build stronger and more flexible materials. A team of researchers from the University of Manchester has now created a record-breaking knot.
The tightest knot ever is also one of the tiniest. Made of strings of molecules braided together, the knot is only 20 nanometres long, and its properties are as yet unknown. But researchers hope that these tied-up molecules could lead to lighter body armour or more flexible surgical sutures. Molecular knots like this are probably more analogous with the knots in mathematics, which are closed loops twisted into different shapes, than with the knots in your phone charger's cord. The first molecular knot – one of the most mathematically simple kinds called a trefoil knot – was tied in 1989.
Chemists have tied the tightest knot yet, a nano-sized structure with eight crossings and just 192 atoms. The advance could help researchers learn how to manipulate materials at the atom level to develop stronger, more flexible, and lighter-weight cloth or construction materials. The knot, described in today's issue of the journal Science, measures 20 nanometers in length, about 100,000 times smaller than the head of a pin. Why make a knot that's so small? I'll give you a two-part answer.
Knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. However, the lack of synthetic routes to all but the simplest molecular knots currently prevents systematic investigation of the influence of knotting at the molecular level. We found that it is possible to assemble four building blocks into three braided ligand strands. Octahedral iron(II) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. This approach enables two-step assembly of a molecular 819 knot featuring eight nonalternating crossings in a 192-atom closed loop 20 nanometers in length.
Fret no longer children of planet Earth, as new research from the University of California, Berkeley, has figured out the physics behind why shoelace knots fail and why some shoelaces are more prone to the mistake. No matter how tight you tug, it feels like some shoelaces are doomed to come untied. Fret no longer, as new research from the University of California, Berkeley, has figured out the physics behind why the knots fail and why some shoelaces are more prone to the mistake. While the poetic inevitability of the slipup may provide comfort to those afflicted by wayward shoelaces, the research published Tuesday in the Proceedings of the Royal Society of London A may also provide clues for building soft, lifelike robots. Mechanical engineer Oliver O'Reilly began looking into this telltale problem three years ago, after trying to teach his young daughter to tie her shoes.