Statics and Dynamics of Colloidal Particles in Liquid Crystals – Oleg Lavrentovich

Date: Thu. November 29th, 2012, 4:15 pm-5:15 pm
Location: Rockefeller 301

Colloids and liquid crystals are two important classes of soft matter, usually explored independently of each other. The most studied colloids represent a dispersion of solid or liquid particles in an isotropic fluid such as water. The simplest liquid crystal, a nematic, is a fluid with long-range orientational order of molecules. This presentation reviews recent studies of liquid crystal colloids, i.e., dispersions of particles in a liquid crystal. The long-range orientational order imparts anisotropic elastic interactions of colloidal particles [1]. Elastic repulsion from the bounding walls opposes gravity and keeps the particles levitating in the liquid crystal bulk [2]. The levitating particles can be set into motion by applying an electric field. Liquid crystals enable a new mechanism of electrophoresis, in which the particle’s velocity is proportional to the square of the electric field. The latter is dramatically different from the classic electrophoresis with a linear relationship. The nonlinear feature allows one to use an AC driving to maintain steady flows, to move particles that are electrically neutral and to design three dimensional trajectories of their motion.
References:
[1] P. Poulin, H. Stark, T.C. Lubensky and D.A. Weitz, Novel colloidal interactions in anisotropic fluids. Science 275, 1770 (1997).
[2] O.P. Pishnyak, S.V. Shiyanovskii, O.D. Lavrentovich, Inelastic collisions and anisotropic aggregation of particles in a nematic collider driven by backflow, Phys. Rev. Lett. 106, 047801 (2011).
[3] O.D. Lavrentovich, I. Lazo and O.P. Pishnyak, Nonlinear electrophoresis of dielectric and metal spheres in a nematic liquid crystal, Nature 467, 947 (2010).