Measuring Electric-Field-Induced Dipole Moments of Metal-Dielectric Janus Particles in a Nematic Liquid Crystal

Abstract

Janus particles are special types of nanoparticles or microparticles possessing at least two surfaces with distinct physical or chemical properties. The most-studied Janus particles are metal-dielectric particles, in which half the surface of the dielectric particles is coated with a very thin layer of a metal. The external electric field induces a dipole moment, and consequently the particles exhibit self-assembled dynamic structures in concentrated aqueous suspensions. Here we study metal-dielectric Janus particles in a nematic liquid crystal under an ac electric field and demonstrate a method for measuring the effective induced dipole moments of the particles through competition between elastic and electrostatic (Coulomb) forces of the two particles. The calculated polarizability of the particles based on a simple model agrees well with the effective polarizability measured in the experiments. Our findings have important bearing on functional materials based on metal-dielectric Janus particles dispersed in an anisotropic medium.