**Manipulation of Topological Defects in Liquid Crystals**

A topological defect (TD) occurs at a wall, line, or point where the relevant order parameter — in our case the liquid crystal’s orientational order parameter — becomes ill-defined, and where this singularity cannot be removed by varying the order parameter continuously. Studies of TDs can be used to obtain values of elastic constants and surface tension, and can serve as an important signature when determining the symmetry of phases. Defect dynamics provide another important field of study, as defect motion is extremely sensitive to boundary effects and provides information about surfaces and impurities. Defects and boundaries can serve as traps for micro- and nanoparticles, as the presence of the particles can reduce or eliminate the energy associated with the defect core.

I first will present a general introduction to topological defects and liquid crystals, and then show how one can pattern regular arrays of TDs at the nanoscale to understand the various mechanisms that relieve the diverging strain energy associated with the defect’s core. Finally, I will discuss recent results on bistable control of the defect’s architecture, and plans for nanoparticle trapping experiments planned for the International Space Station.