Figure 15.

Rewiring of knots and links using laser tweezers. (a) A right-handled Trefoil knot is realized on a 4 × 3 colloidal array. The dashed circles indicate a unit tangle that can be rewired with the laser beam. The tangle consists of two perpendicular line segments and the surrounding molecular field. (b) By rewiring the unit tangle that corresponds to a 2π/3 rotation of the encircled tetrahedron, a new composite knot, shown in (c), is knitted. The sequence of tangle rewirings in (b–f) results in switching between the knots and links, demonstrated in (a,c,e). The procedure for rewiring the topological defect loops is not an exact and repeatable procedure, but is rather a skill that is learned after trying and repeating a good number of experiments. It is necessary to learn how to adjust the applied power, the position of the tweezers’ focus and the direction of the movement of the trap that is cutting the defect loop. Scale bars, 5 µm. Adapted from Ref. [87].