Optical trapping, manipulation, and 3D imaging of disclinations in   liquid crystals and measurement of their line tension
  We demonstrate optical trapping and manipulation of defects and transparent microspheres in nematic liquid crystals (LCs). The three-dimensional director fields and positions of the particles are visualized using the Fluorescence Confocal Polarizing Microscopy. We show that the disclinations can be manipulated by either using optically trapped colloidal particles or directly by tightly-focused laser beams. We employ this effect to measure the line tensions of disclinations. 
Ivan I. Smalyukh, Bohdan I. Senyuk, Sergij V. Shiyanovskii, Oleg D.   Lavrentovich, Andrey N. Kuzmin, Alexander V. Kachynski...