Photo-Embossed Surface Relief Structures with Improved Aspect Ratios and Their Applications in Liquid Crystal Devices

Photo-embossing has been developed as a convenient and economical method for creating complex surface relief structures in polymer films. The pursuit for large aspect ratios of the photo-embossed structures has never stopped. Here, we demonstrate a simple strategy to obtain improved aspect ratios by adding a quick solvent developing step into the photo-embossing process. A good solvent for the monomer is used to remove unreacted monomers from the unexposed region, resulting in deepened valleys of the surface reliefs. In a polymer film as thin as 2.5 µm, the height of the surface reliefs can be increased by a factor of three to around 1.0 µm. This strategy is also shown to be compatible with other methods used to improve the aspect ratios of the photo-embossed structures. Lastly, we employ these surface relief structures in the fabrication of liquid crystal (LC) devices and investigate their performances for visible light regulation.

Information systems in geotechnics

The article considers the information modeling of buildings together with the foundation within the information system and the stages of its implementation. The workflow for building a 3D geotechnical model includes surface relief data, field and laboratory test data, soil lithology, geometric characteristics of the foundation structure and load. Automated systems with processing and interpretation of test data are used to determine the characteristics of soils. Mathematical modeling of the behavior of the foundations of the foundations with various input data is performed using analytical solutions and numerical methods. The natural heterogeneity of soil properties and its impact on the behavior of buildings is estimated by the sensitivity indicator of the foundation-foundation system by introducing virtual workings between the existing normative ones and the subsequent calculation of the precipitation and roll of the foundation.

High-power single-mode 894 nm VCSELs operating at high temperature (> 2 mW @ 365 K)

In this study, we realize the high-power output of a single-mode 894 nm vertical-cavity surface-emitting laser (VCSEL) at high temperature. The effects of the dimensional parameters of oxide aperture and surface relief on the transverse mode and threshold gain of VCSEL were analyzed. Through collaborative optimization of the oxide aperture and relief, the VCSEL with 8 µm oxide aperture diameter and 5 µm surface relief inner diameter can operate at high temperature of 365 K with single-mode output power of 2.02 mW and side-mode suppression of 29.2 dB.

Anomalous evolution of the ion-induced surface relief of highly oriented pyrolytic graphite

The modification of the surface of highly oriented pyrolytic graphite (HOPG) under 10, 20 and 30 keV Ar+ ions irradiation with fluence 1018 cm−2 at the irradiation temperature of 250°C has been studied experimentally. An anomalous growth of the ion-induced surface relief of HOPG have been found. This effect, like the well-known effect of anomalous deep embedded argon ions in HOPG, is analyzed within the framework of plastic deformation mechanisms in graphite.

Influence of the nature of a polysaccharide on the surface-morphological and physicomechanical properties of sol–gel plates

Thin-film sol–gel plates based on chitosan and glucomannan polysaccharides in a wide range of compositions were obtained. The effect of the polysaccharide component on the SEM surface morphology and physicomechanical properties was evaluated. It was found that the introduction of the polysaccharide glucomannan (and/or Aloe Vera juice) into the composition of chitosan sol–gel plates increased the elastoplastic characteristics of the samples and had a significant effect on the surface relief of their solid phase. The obtained structures can be used for the design of bioadhesive sensor coatings with a high therapeutic effect, which is an urgent area for theranostics and regenerative medicine.

Fourier Transformation method for solving integral equation in the 2.5D problem of electric sounding

The paper discusses a method for solving an integral equation for calculating a three-dimensional electric field in a medium with a two-dimensional geometry based on the Fourier transform. The results of the numerical solution of the transformed integral equation and the original integral equation for the medium with the surface relief are compared. The original equation was solved using parallelization technologies on a system with shared memory. A significant performance improvement based on the transformed equations, including in comparison with the parallel version of the program for the original integral equation, is shown.

Morphological Features of Fruits and Seeds of Some Species of the Genus Crataegus L. of the Flora of Ukraine

The genus Crataegus L. is one of the largest species in the family Rosaceae Juss. The fruits are used as medicinal raw materials ( Crataegus fructus ), as they contain a set of biologically active compounds. The genus is voluminous and taxonomically problematic due to significant variability, hybridization, apomixis, and polyploidy. As a result, it is difficult to determine the species of the genus. Species of the genus have a number of diagnostic features, one of which is a distinct fruit with seeds. The aim of our study was to identify and compare the diagnostic features of the fruits of seven species of the genus Crataegus flora of Ukraine, which are most often used as medicinal raw materials and are the most common in Ukraine – Crataegus laevigata , C. monogyna , C. pentagyna , C. pseudokyrtostyla , C. sanguinea , C. fallacina , and C. rhipidophylla . The study was performed using scanning and digital microscopy, and descriptions were made by standard methods. As a result, we identified features that clearly distinguished the studied species from each other. We identified mature fruits that contain only one pyrene ( C. monogyna , C. pseudokyrtostyla , C. fallacina , and C. rhipidophylla ), and several pyrenes ( C. laevigata , C. pentagyna , and C. sanguinea ) among the studied species of the genus. The studied species are characterized by spherical and ellipsoidal fruits. The predominant color is fulvous/brown with different shades, but almost-black fruits of the species C. pentagyna are well distinguished. Fruits of all studied species of the genus are fleshy, except C. sanguinea , which is floury. The species is characterized mainly by yellow flesh fruits, except C. pentagyna , which has ribbed fruits. The fruits of C. monogyna plants differ from those of other studied species by the spinous-tuberous surface relief. Pyrenes of triangular shape are observed only in C. pentagyna . We suggest that these features can be used as additional diagnostic tools to determine the species of the genus Crataegus flora in Ukraine.

Icephobic Performance of Combined Fluorine-Containing Composite Layers on Al-Mg-Mn–Si Alloy Surface

This paper presents the results of an evaluation of anti-icing properties of samples obtained by plasma electrolytic oxidation (PEO) with a subsequent application of superdispersed polytetrafluoroethylene (SPTFE) and polyvinylidenefluoride (PVDF). A combined treatment of the samples with SPTFE and PVDF is also presented. It is revealed that impregnation of a PEO layer with fluoropolymer materials leads to a significant increase in surface relief uniformity. Combined PVDF–SPFTE layers with a ratio of PVDF to SPTFE of 1:4 reveal the best electrochemical characteristics, hydrophobicity and icephobic properties among all of the studied samples. It is shown that the decrease in corrosion current density Ic for PVDF–SPFTE coatings is higher by more than five orders of magnitude in comparison with uncoated aluminum alloy. The contact angle for PVDF–SPFTE coatings attain 160.5°, which allows us to classify the coating as superhydrophobic with promising anti-icing performance. A treatment of a PEO layer with PVDF–SPFTE leads to a decrease in ice adhesion strength by 22.1 times compared to an untreated PEO coating.