Colloidal liquid crystals offer a route to change physical properties and create micro and nano structures. Optical methods only characterise relatively simple colloidal systems. More complex systems require powerful data analytic methods. We present a new approach using Topological Data Analysis to reveal the structural and morphological features in a nematic liquid crystal doped with gold nanoparticles confined in a thin capillary, including the changes occurring during phase transitions. Our topological framework allows us to identify distinct temperature-induced macroscopic states, obtain a geometric representation of the time-dependent topological states and identify several configurations with different degrees of symmetry and order.
Photonic liquid crystal fibers (PLCFs) have been studied for over a decade as an emerging field of sensing and telecommunication devices. Exciting properties of liquid crystals (LCs) infiltrating photonic crystal fibers (PCFs) can be additionally tuned by doping with various materials that are sensitive to external influences, such as an electric field or temperature. Among them, metallic nanoparticles (NPs) are gathering a great interest, due to their potential applications. NPs can be used to highly influence material properties of LCs as dielectric anisotropy, elastic constants, and viscosity. This may lead to many desirable effects, such as a decrease of the Fredericks threshold voltage or reduction of LC switching times. In this paper we doped a nematic LC with 2-nm gold (Au) and 8-nm silver (Ag) NPs, and infiltrated the prepared mixtures into photonic crystal fibers. We examined the influence of this doping in two different electric field systems, one with two flat copper electrodes, and second with four copper microelectrodes. Our results indicate that metallic NP (both Au and Ag) doping enhances sensitivity of the PLCF-based sensors to an electric field and decreases the threshold voltage. Additionally, due to smaller distances between the electrodes, the proposed four microelectrode system requires lower voltages to effectively tune the PLCF.
In this work we studied a newly reported class of nonlinear effects observed in 5CB liquid crystals doped with gold nanoparticles (GNPs). The size of the GNP was determined by direct TEM imaging and by X-ray scattering of the diluted NP solution. GNPs was coated by thiols with the ratio of mesogenic to n-alkyl thiols varying from 1:2 to 1:1. The research involved comparing properties of both undoped and doped 5CB (nematic LC) by infiltrating LC cell and microholes of the photonic crystal fiber (PCF) separately. In our experiment the PCF fiber type LMA-10 made by NKT Photonics as host material has been used.
Photonic liquid crystal fiber has been intensively investigated in last few years. It has been proved that guiding properties of such fibers could be tuned with an electric field. In particular efficient tuning could be obtained if multi-electrode system allowing for dynamic change of not only intensity of the electric field, but also its direction. In this work we report a simple to build four electrode system, which is based on a precisely aligned four cylindrical microelectrodes. As an electrodes we use enameled copper wire with diameter adequate to the diameter of the fiber to be tuned. To ensure uniform and parallel alignment of the wires a special micro-profiles has been designed and then produced with filament 3D printer. The possibility of the dynamic change of the electric field direction in such scalable and cost effective electrode assembly has been experimentally confirmed.
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