12 research outputs found
Inelastic Collisions and Anisotropic Aggregation of Particles in a Nematic Collider Driven by Backflow
We design a nematic collider for controlled out-of-equilibrium anisotropic
aggregation of spherical colloidal particles. The nematic surrounding imparts
dipolar interactions among the spheres. A bidirectional backflow of the nematic
liquid crystal (NLC) in a periodic electric field forces the spheres to collide
with each other. The inelastic collisions are of two types, head-to-tail and
head-to-head. Head-to-tail collisions of dipoles result in longitudinal
aggregation while head-to-head collisions promote aggregation in the
transversal direction. The frequency of head-to-head collisions is set by the
impact parameter that allows one to control the resulting shape of aggregates,
their anisotropy and fractal dimension
Levitation, Lift, and Bidirectional Motion of Colloidal Particles in an Electrically Driven Nematic Liquid Crystal
We study electric-field-induced dynamics of colloids in a nematic cell, experimentally and by computer simulations. Solid particles in the nematic bulk create director distortions of dipolar type. Elastic repulsion from the walls keeps the particles in the middle of cell. The ac electric field reorients the dipoles and lifts them to top or bottom, depending on dipole orientation. Once near the walls, the colloids are carried along two antiparallel horizontal directions by nematic backflow. Computer simulations of the backflow agree with the experiment