The ability to control regular spatial arrangements of particles is one of the central issues of the ‘‘bottom-up’’ approach to nanotechnology. Self-assembling of colloidal particles has arisen as a very hopeful alternative. However, these studies are typically performed in aqueous media where the interparticle interactions are poorly controlled. In this project we will study the interactions between particles trapped in a novel challenging interface consisting of a nematic liquid crystal and an isotropic fluid. Our fist objective is to exploit the unique properties of the nematic phase to achieve a high degree of control in the interaction of the particles trapped in the interface. In this geometry, the particle-particle interactions are triggered by capillary forces resulting from the interface distortion. We will employ electric/magnetic fields as well as sophisticated anchoring conditions for the nematic to tailor these distortions in terms of range, amplitude, and directionality. We will address questions concerning crystallization, melting and aggregation in a 2-dimensional space. To quantify the interface deformations we will use a technique based on Michelson interferometry and optical tweezers. Our second objective is to study the effect of particle anisotropy in the formation of ordered patterns. We will consider both spherical particles with anchoring gradients and particles with exotic geometry. Despite the richness of behavior expected, the relationship between the anisotropy of colloids and their collective behavior when trapped in an interface is still largely unknown. Finally, we will analyze how the behavior of the colloidal particles is affected by the interface curvature. Some elegant theoretical predictions show that equilibrium positions are located in the points of constant Gaussian curvature. This behavior is still completely unexplored experimentally and may find practical relevance in pickering emulsions, solid stabilized foams, etc.
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