Assembly of microparticles on thin smectic films

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Colloidal particles organize spontaneously at fluid interfaces owing to a variety of interactions to form well organized structures that can be exploited to synthesize advanced materials. While the physics of colloidal assembly at isotropic interfaces is well understood the mechanisms that govern interactions between particles at liquid crystal interfaces are not yet clearly established. In particular smectic liquid crystal films offer important degrees of freedom that can be used to direct particles into new structures. In this work we report on the behavior of micrometric silica spheres with homeotropic anchoring confined within or at interfaces of smectic films. We study the interactions and self-assembly of these particles as a function of film thickness in both supported and in free standing films. When particles are captured in thin membranes they induce distortions of the smectic interface to satisfy wetting properties at particle boundaries leading to capillary interactions between the particles. These capillary interactions compete with elastic interactions owing to particle-induced distortions in the smectic layers. The resulting potential drives assembly of the spheres into different structures ranging from 1D chains to 2D aggregates. By increasing the thickness of the smectic we control the formation of focal conic domains (FCDs) and their organization. The FCDs interact with particles at the interface and can be used to direct the formation of complex particle structures. Recent progress in understanding the process of particle self-organization is presented.