Colloids and Topological Defects in Liquid Crystals
Date and time:
Friday, August 31, 2012 - 3:30pm
Liquid crystals and colloids find increasingly important applications in science and technology, ranging from information displays to direct probing of kinetic processes in crystals and glasses, and to modeling of dynamics of comic strings in the Early Universe cosmology. This lecture will discuss dispersions of complex-shaped particles in liquid crystalline host media and the interplay of topology of the colloidal particles and topological defects that they induce in the director field describing spatial changes of the liquid crystalline molecular alignment. In this study, we use colloidal particles with a different number of handles and having genus g=0-5. When introduced into a nematic liquid crystal, these particles induce three-dimensional director structures and topological singularities that minimize elastic energy for given boundary conditions at the colloidal surfaces and also satisfy topological constrains. By means of electric field, photothermal melting, and laser tweezing, we transform particle-induced structures and defects between multiple states and show that their net topological hedgehog charge always obeys predictions of Gauss-Bonnet and Poincaré-Hopf index theorems. The lecture will conclude with a discussion of how our findings may enable new applications of colloids and liquid crystals ranging from optically- and electrically-addressed topological memory devices to experimental exploration of topological manifolds using soft matter systems.