Fabrication of Arrays of Topological Solitons in Patterned Chiral Liquid Crystals for Real-Time Observation of Morphogenesis.

Topological solitons have knotted continuous field configurations embedded in a uniform background, and occur in cosmology, biology, and electromagnetism. However, real-time observation of their morphogenesis and dynamics is still challenging because their size and timescale are enormously large or tiny. Liquid crystal (LC) structures are promising candidates for a model-system to study the morphogenesis of topological solitons, enabling direct visualization due to the proper size and timescale. Here, a new way is found to rationalize the real-time observation of the generation and transformation of topological solitons using cholesteric LCs confined in patterned substrates. The experimental demonstration shows the topologically protected structures arise via the transformation of topological defects. Numerical modeling based on minimization of free energy closely reconstructs the experimental findings. The fundamental insights obtained from the direct observations pose new theoretical challenges in understanding the morphogenesis of different types of topological solitons within a broad range of scales.

Nanoscratch-Directed Self-Assembly of Block Copolymer Thin Films.

Directed self-assembly (DSA) of block copolymer (BCP) thin films is of particular interest in nanoscience and nanotechnology due to its superior ability to form various well-aligned nanopatterns. Herein, nanoscratch-DSA is introduced as a simple and scalable DSA strategy allowing highly aligned BCP nanopatterns over a large area. A gentle scratching on the target substrate with a commercial diamond lapping film can form uniaxially aligned nanoscratches. As applied in BCP thin films, the nanoscratch effectively guides the self-assembly of overlying BCPs and provides highly aligned nanopatterns along the direction of the nanoscratch. The nanoscratch-DSA is not material-specific, allowing more versatile nanofabrication for various functional nanomaterials. In addition, we demonstrate that the nanoscratch-DSA can be utilized as a direction-controllable and area-selective nanofabrication method.

Periodic Arrays of Chiral Domains Generated from the Self-Assembly of Micropatterned Achiral Lyotropic Chromonic Liquid Crystal.

Achiral building blocks forming achiral structures is a common occurrence in nature, while chirality emerging spontaneously from an achiral system is usually associated with important scientific phenomena. We report on the spontaneous chiral symmetry-breaking phenomena upon the topographic confinement of achiral lyotropic chromonic liquid crystals in periodically arranged micrometer scale air pillars. The anisotropic fluid arranges into chiral domains that depend on the arrangement and spacing of the pillars. We characterize the resulting domains by polarized optical microscopy, support their reconstruction by numerical calculations, and extend the findings with experiments, which include chiral dopants. Well-controlled and addressed chiral structures will be useful in potential applications like programmable scaffolds for living liquid crystals and as sensors for detecting chirality at the molecular level.

Topological defects and geometric memory across the nematic-smectic A liquid crystal phase transition.

We study transformations of self-organised defect arrays at the nematic-smectic A liquid crystal phase transition, and show that these defect configurations are correlated, or "remembered", across the phase transition. A thin film of thermotropic liquid crystal is subjected to hybrid anchoring by an air interface and a water substrate, and viewed under polarised optical microscopy. Upon heating from smectic-A to nematic, a packing of focal conic domains melts into a dense array of boojums-nematic surface defects-which then coarsens by pair-annihilation. With the aid of Landau-de Gennes numerical modeling, we elucidate the topological and geometrical rules underlying this transformation. In the transition from nematic to smectic-A, we show that focal conic domain packings are organised over large scales in patterns that retain a geometric memory of the nematic boojum configuration, which can be recovered with remarkable fidelity.

Nanoscratching technique for highly oriented liquid crystal materials.

A simple, fast, and cost-effective technique to obtain highly oriented thermotropic and lyotropic liquid crystal (LC) phases using a simple nanoscratching method is presented. Highly aligned linear nanogrooves are fabricated by scratching substrates such as normal, indium tin oxide (ITO), curved glasses, and ITO-coated polyethylene terephthalate (PET) film using diamond lapping films. To demonstrate the feasibility of the platform, typical thermotropic and lyotropic LC materials in the nematic phase are used to demonstrate the well-aligned domains along with the resulting scratched nanogrooves. The polarised optical microscopy (POM) images show excellent dark and bright states depending on the sample rotation, proving that the LC molecules are well aligned. The electro-optical performance of the twisted nematic (TN) mode LC display fabricated using the nanogrooves is also measured and indicates reliable results compared with that of the conventional device. Indeed, scratch-induced nanogrooves are well generated on the curved substrate and ITO-coated PET film to show versatility of our technique. Our platform can suggest a new nanofabrication way to make various electro-optical devices as well as other patterning applications.

Grooving of nanoparticles using sublimable liquid crystal for transparent omniphobic surface.

Hierarchical assembly of nanoparticles (NPs) is of interest for omniphobic surfaces in the way that hierarchical scale roughness possibly provides effective liquid repellency and also it is relatively easy to build large-area coatings via the bottom-up assembly process. However, all NP assemblies often lacks mechanical robustness. Hence, the development of the effective fabrication method to make well-deposited hierarchical NPs assembly is demanded. In this report, we have demonstrated an all-NP three-dimensional hierarchical surface that is omniphobic yet highly transparent and mechanically robust. By taking advantage of sublimation and recondensation of smectic A liquid crystals (LCs) in a simple thermal annealing process, we patterned NP aggregates in one-dimensional grooves directed by LCs. The resultant groove-like NP-assembled surface showed omniphobicity, repelling water, glycerol, ethylene glycol, and olive oil (with contact angle of 156.5°, 147°, 136.5°, and 123.2°, respectively) because of the low surface energy of the fluorinated NPs and dual roughness. The coating is highly transparent with ∼90% transmittance in the visible wavelength. We investigate the mechanical robustness of the all NP coatings by sand abrasion, which shows nearly identical omniphobicity and transparency after the sand abrasion.

The relationship between normal serum uric acid and nonalcoholic fatty liver disease.

The objective of the present study was to determine the relationship between serum uric acid (SUA) level and the presence of nonalcoholic fatty liver disease (NAFLD). We analyzed data of 9,019 Koreans who visited a health check up center. The SUA levels of all of these subjects were within the normal range. The participants were divided into 4 groups according to the quartiles of the SUA levels for both sexes. Hepatic steatosis was diagnosed on the basis of ultrasonographic findings. Multivariate logistic regression modeling was performed across the SUA quartiles. The presence of NAFLD and metabolic abnormalities were found significantly in subjects with high-normal SUA levels. After adjustment for age, metabolic components, and the liver-function test, the adjusted odds ratio (OR, 95% CIs) for the presence of NAFLD in the subjects with the highest SUA level was 1.46 (1.17-1.82) for men and 2.13 (1.42-3.18) for women, as compared to the subjects with the lowest SUA level. Our results suggest that increased SUA concentrations, even within the normal range, are independently associated with the presence of NAFLD.

Effects of the NADPH oxidase p22phox C242T polymorphism on endurance exercise performance and oxidative DNA damage in response to aerobic exercise training.

We examined the effects of the NADPH oxidase p22phox C242T polymorphism on endurance exercise performance and oxidative DNA damage in response to acute and chronic exercises. One hundred three subjects were recruited, among which 26 healthy subjects (CC: 12, TC: 12, and TT: 2) were studied during rest, exercise at 85% VO(2)max, and recovery before and after 8 weeks of tread-mill running. Lymphocyte DNA damage increased significantly in response to exercise (p < 0.05). There were no significant differences in plasma MDA, SOD concentrations and lymphocyte DNA damage between CC genotype and T allele group, but significant endurance training differences were observed. Endurance training increased exercise time to exhaustion in both the CC genotype and T allele groups (p < 0.05) but no significant difference was found between groups. The results of the current study with young, healthy, Korean men are interpreted to mean that 1) the majority had the CC genotype of the NADPH oxidase p22phox C242T polymorphism (82.5%: CC, 15.5%: TC, 1.9%: TT), 2) acute exercise increased lymphocyte DNA damage, 3) endurance training significantly increased exercise time to exhaustion, and alleviated lymphocyte DNA damage, and 4) The NADPH oxidase p22phox C242T polymorphism, however, did not alter lymphocyte DNA damage or exercise performance at rest, immediately after exercise, or during recovery.

Fluid replacement following dehydration reduces oxidative stress during recovery.

To investigate the effects of hydration status on oxidative DNA damage and exercise performance, 10 subjects ran on a treadmill until exhaustion at 80% VO(2max) during four different trials [control (C), 3% dehydration (D), 3% dehydration+water (W) or 3% dehydration+sports drink (S)]. Dehydration significantly decreased exercise time to exhaustion (D