Whereas many past studies of electrostatic and Van der Waals forces acting between particles in isotropic media have been reported, forces in anisotropic media have not been widely examined even though they appear to offer new ways to design and engineer interparticle forces (for example, to control the stability of a dispersion of particles). 

The presence of liquid crystalline solvent between particles leads to new types of effective forces that are mediate by distortion of the liquid crystal between the particles. In some cases, the distortion of the liquid crystal becomes discontinuous and gives rise to a so-called topological defect.

We have developed a model experimental system that is based on solid particles with well-defined shape, size and surface chemistry. As shown in Figure 1, we have observed Saturn-ring-shaped defects to form about solid particles in liquid crystalline solvents. By controlling the chemistry of the surface of the particles, we have demonstrated that it is possible to control the types of defect that forms in the liquid crystal near each particles. These defects determine the nature of the inter-particle forces.