Eur. Phys. J. E (2015) 38: 23
https://doi.org/10.1140/epje/i2015-15023-6

Regular Article

Topological binding and elastic interactions of microspheres and fibres in a nematic liquid crystal

¹ J. Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia
² Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000, Ljubljana, Slovenia

^* e-mail: igor.musevic@ijs.si

Received: 23 December 2014
Revised: 13 February 2015
Accepted: 20 February 2015
Published online: 30 March 2015

Abstract

We present a detailed analysis of topological binding and elastic interactions between a long, and micrometer-diameter fiber, and a microsphere in a homogeneously aligned nematic liquid crystal. Both objects are surface treated to produce strong perpendicular anchoring of the nematic liquid crystal. We use the opto-thermal micro-quench of the laser tweezers to produce topological defects with prescribed topological charge, such as pairs of a Saturn ring and an anti-ring, hyperbolic and radial hedgehogs on a fiber, as well as zero-charge loops. We study the entanglement and topological charge interaction between the topological defects of the fiber and sphere and we observe a huge variety of different entanglement topologies and defect-mediated elastic bindings. We explain all observed phenomena with simple topological rule: like topological charges repel each other and opposite topological charges attract. These binding mechanisms not only demonstrate the fascinating topology of nematic colloids, but also open a novel route to the assembly of very complex topological networks of fibers, spheres and other objects for applications in liquid crystal photonics.