We show how to easily generate point defects called hedgehogs, in the so-called quasi-planar texture --the dowser state-- of a nematic layer confined between surfaces with homeotropic anchoring conditions. We point out that the dowser texture can be preserved infinitely in spite of its higher energy with respect to the homogeneous homeotropic texture. For topological reasons the dowser state in a squeezed droplet must contain at least one hedgehog. We submitted this hedgehog to a rotating magnetic field and controlled the continuous evolution, transitioning continuously between radial, hyperbolic and circular hedgehogs, which, just as in previous experiments by Lavrentovich et al., are topologically equivalent states. The dynamics of this transformation is shown to be directly sensitive to energy costs of different geometric configurations of the hedgehog defect and therefore can be used as a rough probe for elastic constants; knowing the principal elastic constants K, one can retrieve information about the K constant. We propose also a method of generation of hedgehog pairs by application of a Poiseuille flow to a dowser state wound by a rotating magnetic field.

Microfibers with their elongated shape and translation symmetry can act as important components in various soft materials, notably for their mechanics on the microscopic level. Here we demonstrate the mechanical response of a micro-object to imposed chirality, in this case, the tilt of disclination rings in an achiral nematic medium caused by the chiral surface anchoring on an immersed microfiber. This coupling between chirality and mechanical response, used to demonstrate sensing of chirality of electrospun cellulose microfibers, is revealed in the optical micrographs due to anisotropy in the elastic response of the host medium. We provide an analytical explanation of the chirogyral effect supported with numerical simulations and perform an experiment to test the effect of the cell confinement and fiber size. We controllably twist the microfibers and demonstrate the response of the nematic medium. More generally the demonstrated study provides means for experimental discrimination of surface properties and allows mechanical control over the shape of disclination rings.