Janus nematic colloids

Abstract

We study the behavior of Janus colloidal particles in the nematic liquid crystal 5CB using polarizing optical microscopy and Landau-de Gennes (LdG) modeling. Different equilibrium orientations of Janus particles and different director field configurations around them are observed, depending on the preparation technique of homeotropic (DMOAP) and planar (Au) hemispheres. Using laser tweezers we measure the interactions between different orientations of Janus nematic colloids, showing a boojum type of interaction in the case of DMOAP/Au capped colloids and dipolar-like attraction for Au/DMOAP capped colloids. We observe a novel type of nematic colloidal particle, called a boojum-ring, characteristic of Au/DMOAP Janus nematic colloids, that is also predicted within the LdG theory for patterned colloidal particles with competing homeotropic and planar surfaces.