Nematic Colloidal Swarms Assembled and Transported on Photosensitive   Surfaces
  We demonstrate a novel method to assemble and transport swarms of colloidal particles by combining liquid crystals enabled electrophoresis and photo-sensitive surface patterning. Colloidal particles are propelled in a nematic liquid crystal via application of an alternating current electric field. Swarms of particles are assembled into a rotating mill cluster, or moved as a whole along predefined paths photo-imprinted on chemically functionalized substrates. This technique represents an alternative approach to fluid based lab-on-a-chip technologies guiding the motion of large ensembles of micrometer scale solid or liquid inclusions. 
Sergi Hern\`andez-Navarro, Pietro Tierno, Jordi Ign\'es-Mullol,   Francesc Sagu\'es
cond-mat.soft