Liquid crystalline superatoms

Mimicking molecular chemistry by using mesoscopic building blocks instead of atoms is one of the central issues of the ‘‘bottom-up’’ approach to nanotechnology. With this approach, predetermined spatial arrangements, such as 3D photonic crystals or metamaterials, could be realized spontaneously by self-assembly. A major limitation of the self-assembling concept is the difficulty of producing particles able to form bonds along specific directions, as atoms or molecules do. One conceptually novel strategy to overcome this problem is to coat the particles with a thin layer of liquid crystal. When a liquid crystal is confined to a spherical shell, a set of symmetrically positioned topological defects spontaneously appear at specific sites of the sphere, due to geometrical frustrations in the liquid crystal order. Defects are high energy spots suitable for chemical attack that could be functionalized with ligands and act as attractive patches inducing directionality in the particle-particle interactions: the number of defects would set the particle valence, while their positions would set the directions of bonding. A number of different defect structures have already been produced, including the sp, sp2 and sp3 symmetries of carbon atoms, revealing a promising playground for the formation of complex colloidal superlattices. This research project is being funded by the ANR through Grant 13-JS08-0006-01.

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Topological knots in droplets with holes

From a topological point of view, a sphere and a cube are equivalent, since we can transform one into the other through continuous deformations. (...) 

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Frustrated liquid crystalline order in spherical shells

Confining a liquid crystal to a spherical shell usually entails the formation of topological defects, which are part of the ground state of the (...) 

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