title: Janus nematic colloids driven by light.
abstract: We present an experimental analysis of different equilibrium orientations and light driven transformations of Janus particles in the nematic liquid crystal 5CB. Depending on the preparation technique of homeotropic (DMOAP) and planar (Au) hemispheres we have observed two types of director field configurations: dipolar-like in the case of Au/DMOAP capped colloids and boojum-like in the case of DMOAP/Au capped colloids. Using the manipulation of Au/DMOAP capped colloids with laser tweezers we report on light driven irreversible orientational transformations into Saturn-ring and a novel, boojum-ring configuration. On the contrary, boojum-like DMOAP/Au capped colloids can act as rotators when exposed to the laser filed. Observed rotation is continuous around an axis perpendicular to the laser beam axis, with the frequency increasing linearly with the laser power.
authors.affiliation: Institute of Metals and Technology, Ljubljana, Slovenia. marjetka.conradi@imt.si
authors.forename: M
authors.initials: M
authors.lastname: Conradi
authors.forename: M
authors.initials: M
authors.lastname: Zorko
authors.forename: I
authors.initials: I
authors.lastname: Musevic
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry* / Q000528:radiation effects*; D003102:Colloids / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D050866:Liquid Crystals / Q000737:chemistry*; D008422:Materials Testing; D008968:Molecular Conformation / Q000528:radiation effects; D009570:Nitriles / Q000737:chemistry* / Q000528:radiation effects*; D012031:Refractometry
chemical_list: D001713:Biphenyl Compounds; D003102:Colloids; D009570:Nitriles; C433919:4-cyano-4'-pentylbiphenyl