We report on the discovery of light- control of the topological charge in the system of confined nematic liquid crystals, demonstrating that the confinement of space, specifically with microscopic colloidal fibres, affects the later stages of the Kibble-Zurek mechanism which allows for trapping and control of topological defect loops with different values of the topological charge. By using laser tweezers, the dynamics of topologically charged objects can be well manipulated, including in processes of repulsion and annihilation. The structure of ordering fields and the annihilation dynamics are determined also with intensive numerical modelling. More generally, the demonstrated research reveals the sensitivity of the Kibble-Zurek mechanism on the connectedness of space and symmetry-breaking boundary conditions and further provides a new insight into key topological invariants of general topologically conditioned ordering fields.
COBISS.SI-ID: 2786916
The work reports on the mutual knotting of physical knots in the form of microscopic colloidal particles and the field knots in the molecular ordering field of nematic liquid crystal. Microscopic particle-knots are produced via laser two-photon photopolimerisation technique. Numerical modelling is used for characterisation of the structures in the nematic field, especially topological boojum defects and defect lines, which reveals an interesting interplay of knotted particle and field topologies. The research opens a new route for the self-assembly of topological superstructures and for modelling of other physical systems with similar topological characteristics. The paper was additionally highlighted with the Front Cover of Nature Materials issues and with a News and Views article by Prof. W.T.M. Irvine from the University of Chicago, who is one of the world leading experts on experimental topology of complex fields.
COBISS.SI-ID: 2630244
Here, we show with numerical modeling that quasicrystalline colloidal lattices can be achieved in the form of original Penrose P1 tiling by using pentagonal colloidal platelets in layers of nematic liquid crystals. The tilings are energetically stabilized with binding energies up to 2500 kT for micrometer-sized platelets and further allow for hierarchical substitution tiling, i.e., hierarchical pentagulation. Quasicrystalline structures are constructed bottom-up by assembling the boat, rhombus, and star maximum density clusters, thus avoiding other (nonquasicrystalline) stable or metastable configurations of platelets. Finally, the design of the quasicrystalline tilings as platelets in nematic liquid crystals is inherently capable of a continuous variety of length scales of the tiling, which could allow for the design of quasicrystalline photonics at multiple frequency ranges.
COBISS.SI-ID: 2638948
Here we demonstrate that liquid crystal droplets deposited on microthin biofibers—including spider silk and cellulosic fibers—reveal characteristics of the fibers’ surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. The nematic droplets as sensors also directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization.
COBISS.SI-ID: 2917220
We explore with numerical modelling the templated blue phases. By tailoring the anchoring conditions of the polymer matrix surfaces we predict orientational ordering different from those of bulk blue phases, effectively indicating novel optical blue-phase like materials. Optical Kerr response of templated blue phases is explored, finding large Kerr constants and notable dependence on the surface anchoring strength. More generally, the presented numerical approach is aimed to clarify the role and actions of templating polymer matrices in complex chiral nematic fluids, and further to help design novel template-based materials from chiral liquid crystals.
COBISS.SI-ID: 2850916