Using high power laser tweezers we have created and stabilized topological defect pairs that are pinned to the microfibre in the nematic LC. Defect pairs can be opositely charged topological loops or points. We have study their stability and annihilation process. Experimental results were described using numerical modelling in the frame of Landau-de Gennes theory.
COBISS.SI-ID: 2786916
Nematic braids are reconfigurable knots and links formed by the disclination loops that entangle colloidal particles dispersed in a nematic liquid crystal. We focus on entangled nematic disclinations in thin twisted nematic layers stabilized by 2D arrays of colloidal particles that can be controlled with laser tweezers. We take the experimentally assembled structures and demonstrate the correspondence of the knot invariants, constructed graphs, and surfaces associated with the disclination loop to the physically observable features specific to the geometry at hand. The nematic nature of the medium adds additional topological parameters to the conventional results of knot theory, which couple with the knot topology and introduce order into the phase diagram of possible structures. The crystalline order allows the simplified construction of the Jones polynomial and medial graphs, and the steps in the construction algorithm are mirrored in the physics of liquid crystals.
COBISS.SI-ID: 2787940
The new method for the realignment of nematic liquid crystals in surface stabilized displays was presented. The realignment is carried out by controlled moving of IR laser beam, which reorients LC molecules and consequently the aligning polymer layer due to the surface memory effect. In this way individual pixels can be created, what can be used in production of advanced LCDs.
COBISS.SI-ID: 28524839
Cholesteric blue phases of a chiral liquid crystal are interesting examples of self-organised threedimensional nanostructures formed by soft matter. Recently it was demonstrated that a polymer matrix introduced by photopolymerization inside a bulk blue phase not only stabilises the host blue phase significantly, but also serves as a template for blue phase ordering. We show with numerical modelling that the transfer of the orientational order of the blue phase to the surfaces of the polymer matrix, together with the resulting surface anchoring, can account for the templating behaviour of the polymer matrix inducing the blue phase ordering of an achiral nematic liquid crystal. Furthermore, tailoring the anchoring conditions of the polymer matrix surfaces can bring about orientational ordering different from those of bulk blue phases, including an intertwined complex of the polymer matrix and topological line defects of orientational order. Optical Kerr response of templated blue phases is explored, finding large Kerr constants in the range of K = 2–10x10-9 mV2 and notable dependence on the surface anchoring strength.
COBISS.SI-ID: 2850916
Devices demonstrated n-type characteristics with ON/OFF current ratios of more than 103, greatly exceeding the best prior report of 60 in the MoS2 nanotubes prepared in other ways. Current densities were 1.02 µA/µm and 0.79 µA/µm at VDS=0.3V and VBG=1V, respectively. Photocurrent measurements conducted on a MoS2 nanotube FET using Ti/ Au contacts revealed short-circuit photocurrent of tens of nanoamps under an excitation optical power of 78 µW and 488 nm wavelength, which corresponds to a responsivity of 460 µA/W.
COBISS.SI-ID: 28399399