Nematic Colloidal Crystals and Superstructures
I. Musevic1,2J.Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
2Faculty of Mathematics and Physics, University of Ljubljana, Jadraska 19, SI-1000, Ljubljana, Slovenia
1

1. INTRODUCTION

We shall discuss the general properties and recent development in the field of nematic colloids, which
are dispersions of microparticles in a nematic liquid crystal. As the nematic liquid crystal is anorientationally ordered fluid, it interacts with the surfaces of inclusions that impose a preferential order at acurved interface. This interaction generates topological defects, which are responsible for structural forces
between dispersed microparticles [1].
2. STRUCTURAL FORCES AND COLLOIDAL ASSEMBLY IN NEMATIC LIQUID CRYSTALSThe structural forces in liquid crystals are extremely strong, anisotropic and long-range, and are responsiblefor directed assembly of a broad variety of colloidal superstructures in liquid crystals: 2D colloidal crystals[2], colloidal wires, assembled by entangled topological defects [3], superstructures in the mixtures of large
and small colloidal particles [4] and a broad variety of 2D nematic colloidal crystals [5]. In all cases, thecolloidal binding energy is several orders of magnitude stronger compared to water based colloids, and could
provide assembly of nanometer-sized colloidal particles of various shapes [6]. The methods of manipulationof microparticles and the mechanisms of their assembly in the nematic liquid crystal will be discussed.
Comparison between theoretical predictions based on Landau-de Gennes theory and the experiments will beaddressed. Possible application of directed and robust colloidal assembly for photonic devices will bediscussed, as it has recently been shown, that a single nematic microdroplet in a liquid or polymer matrix
provides a novel class of tunable optical microresonators. Light can be trapped in a microdroplet due to thetotal internal reflection and the resonant eigenmodes can be tuned by an external electric field [7]. This could
be a basic tunable optical resonant element for future technological platform for soft matter photonic devices.
ACKNOWLEDGEMENT
The author would like to thank Miha Škarabot for his valuable contribution to this work. Contributions ofMiha Ravnik, Slobodan Žumer, Uroš Tkalec, Igor Poberaj, Dušan Babič, Natan Osterman, Andriy Nych,
Ulyana Ognysta and Vassili Nazarenko are also acknowledged.
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