PerspectiveApplied Physics

Knot Your Simple Defect Lines?

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Science  01 Jul 2011:
Vol. 333, Issue 6038, pp. 46-47
DOI: 10.1126/science.1208526

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We owe more to knots in our lives than we might appreciate: Simple bows and knots developed into the practical knots of sailors, decorative braids, and, as we are still learning, into the Khipu records of the Incas (see the figure, panel A). The ancient art of weaving became a driving force in the industrial revolution; the Jacquard loom gave us the first inkling of the modern programmable computer; and ancient embroidery, such as the Bayeaux tapestry, imprint the historical record (see the figure, panel B). On page 62 of this issue, Tkalec et al. (1) tie knots in a different type of line—the topological defect lines that form when the ordering of a nematic liquid crystal is disrupted by the addition of colloidal particles. When these lines are manipulated with laser tweezers, they can be woven into arbitrarily complex knots and links. Moreover, the formation of these beautiful and stable braided structures is enabled by using a sample cell similar to that commonly used in liquid crystal display technology.