Dispersions of complex-shaped nano- and micro-sized colloidal particles in isotropic and liquid crystalline (LC) hosts have attracted a great deal of interest and may offer a means of self-assembly of materials with novel optical and mechanical properties. Methods for optical manipulation of colloidal shapes that would allow one to explore their practical utility and physical underpinnings behind such shape-dependent interactions are in a great demand. This lecture will describe fabrication of colloidal particles with complex three-dimensional shapes and also optical control of shape of LC elastomeric microparticles while they are dispersed in nematic and cholesteric LCs. Elastomeric colloids with cylindrical initial shapes and nematic director along the cylinder axis are obtained by means of soft lithography, polymerization in a strong magnetic field, and subsequent infiltration with gold nanospheres. By utilizing nanoparticle-mediated photothermal energy transfer from laser light to heat and inherent coupling between the temperature-dependent ordering and shape, we bend and morph the elastomeric microparticles to obtain long-term-stable well-controlled complex particle shapes and LC director fields within and around the particles. We show that laser-induced changes of shape of elastomeric colloids are followed by their spontaneous realignment and transformations of dipolar and quadrupolar director structures in the surrounding nematic host. We also demonstrate that elastomeric and metal complex-shaped particles can be rotated and translated using low-frequency electric fields. These findings are explained by use of a simple model based on LC elasticity and may impinge on shape-controlled self-assembly of adaptive composite materials.

Optical control of reconfigurable shape-morphing liquid crystal elastomeric colloids in nematic and cholesteric liquid crystals

245th National Meeting (2013)

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