  Janus particles are special types of nano or micro particles possessing at
least two surfaces with distinct physical or chemical properties. The most
studied Janus particles are the metal-dielectric particles, in which half
surface of dielectric particles is coated with a very thin layer of metals. The
external electric field induces 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 AC electric field and demonstrate a novel method for measuring effective
induced dipole moments of the particles, through competition between elastic
and electrostatic (Coulomb) forces of the two particles. The calculated
polarisability of the particles based on a simple model agrees well with the
effective polarisability measured in the experiments. Our findings have
important bearing on functional materials based on metal-dielectric Janus
particles dispersed in an anisotropic medium.
