Topological transformations of isotropic droplets with breakup and formation of topological defects in a confined nematic geometry†

Confined geometry and surface configuration can induce nontrivial structures and topological transformations between them. Here, we study complex transformations in the two-phase isotropic–nematic region in the confined geometry of a planar optical cell. We investigate the transformation of isotropic droplets induced by the isotropic–nematic transition, and the change of droplet Euler characteristic, accompanied by a change of the number and the total charge of topological defects on the surface of the isotropic droplet. We found that simple and multiple handled toroids with zero and negative Euler characteristics can be formed from sessile isotropic droplets. The complex dynamics of the isotropic–nematic interface were investigated. Rayleigh–Plateau instability with breakup of the toroid and creation of satellite isotropic droplets were found. The observed transformations are discussed on the basis of topology.