Abstract
The aim of this experimental work is to study the behavior of colloids at nematic interfaces. Initially, we examine the behavior of spherical solid particles with strong homeotropic anchoring at an air-nematic interface and we detail the phase behavior of beads. Depending on their area density, the nematic thickness and the anchoring, colloids spontanously form various structures. Using optical tweezers, we determine the pair potential and we discuss the different roles of capillary and elastic forces. We then report the behavior of silica beads at more complex NLC interfaces. By controlling the geometry of the interfaces and the colloids density, with microfluidic techniques, we study the colloidal behavior at the surface of a thin nematic shell. The competition between anchoring conditions at interfaces, nematic elsticity, topological defects and densities of fluids is responsable of the formation of new topological configurations. In this part we discuss the role of colloids in the formation of these structures.