Mutually tangled physical and field knots in nematic colloids
Mutually tangled physical and field knots in nematic colloids have been successfully realized by A. Martinez, M. Ravnik, B. Lucero, R. Visvanathan, S. Žumer and I. I. Smalyukh. The paper Mutually tangled colloidal knots and induced defect loops in nematic fields that has been just published in the high-ranking journal Nature Materials, is the result of a collaboration between the experimental group from University of Colorado at Boulder (USA) and the theory and modelling group from the Faculty of Mathematics and Physics (FMF) at University of Ljubljana. The paper reports on the mutual knitting of physical knots in the shape of micro-particles and knots in the molecular field of nematic liquid crystals. Experimentally, the colloidal particle-knots are produced by laser two-photon photopolymerization technique, allowing also for good control of surface conditions for the nematic field. Numerical modelling is used to explore the structure of the nematic fields, in particular topological "boojum" surface defects and defect lines, which reveals an interesting mutually tangled topology of particle- and field-knots. The demonstrated approach may find uses in self-assembled topological superstructures, in topological scaffolds, and for modelling other physical systems with topologically analogous phenomena.