In this project we study the formation and evolution of topological defects in liquid crystals confined by curved boundaries. Over the last decades liquid crystal research had mainly focused on flat geometries, because of their great importance for information display technologies. But exchanging flat by curved interfaces causes intriguing effects and leads to completely new equilibrium configurations of molecules, which then allow for fascinating new applications and technologies. In our work we focus on nematic or cholesteric liquid crystals in spherical confinement, e.g. droplets or shells, and try to understand and predict the huge variety of polarizing microscopy textures which can be observed in these geometries.

A topological defect can be understood as a singularity in the local orientational order of the nematic phase. Towards the center of such defect the degree of order significantly decreases, while in the defect core the order completely vanishes and renders the molecules randomly oriented. Such defects are often inevitably formed when the liquid crystal is confined by curved boundaries: The interfaces often force a certain orientation to the molecules in their vincinity and this preferred orientation is then transferred into the volume of the LC. However, very often these imposed ordering does allow for a uniform and homogeneous molecular orientation throughout the whole LC volume and defects are formed.


Polarizing Micrographs of a nematic droplet in glycerol. Left: crossed polarizers. Center: parallel polarizers. Right: Crossed Polarizers with quarter-wave plate. In the center of this droplet a topological defect can be found, the surrounding preferred molecular orientation can be deduced by sophisticated polarising microscopy techniques.


Besides experimental studies on defect formation and evolution, we have a strong focus on Numerical Simulations, which allows us even deeper insight into the defect structures of nematic ordering.

Click on the link above or the image to the right for more information on our simulation work.