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Liquids are generally a little too slippery to be tied in knots. But under the right conditions, special types of liquid can knot themselves and then those knots can form crystals. They may be a step toward more energy efficient screens.

The idea of these knotty crystals has been around for more than a century. But earlier attempts to make them have had trouble creating stable knots or getting the knots to take on a crystalline structure . Finally, Jung-Shen Tai and Ivan Smalyukh at the University of Colorado, Boulder, have figured out how.


Their method starts with a liquid crystal. These materials can flow like a liquid, but the molecules within them line up in ordered arrays, instead of being jumbled up like in a regular fluid. Liquid crystals are already used in some flat-screen televisions.

Tai and Smalyukh mixed in chiral molecules, which have an asymmetric “handedness”— think of them like screws, which can only be tightened by turning them one way. The researchers then used electric fields to create little whirlpools of these molecules, which tied themselves into knots and spontaneously assembled into ordered lattices.

The researchers studied three kinds of knot in detail, but they saw hundreds more. Eventually, these crystals made of knots could be used to store information where different knots tied at various locations have specific meanings, Smalyukh says. The information could then be read with a microscope.

Because the knots are tied in materials similar to those that we use for screens, they could be used to make more energy-efficient displays as well. “Once you tie these knots, you cannot easily untie them,” says Smalyukh. “In a single pixel of a display, you could have that knot displaying information and you don’t need to apply any voltage to keep that information displayed, only to change or erase it.”

Journal reference: Science, DOI: 10.1126/science.aay1638