Hexagonal Pattern Research Articles

Directed Self-Assembly by Sparsely Prepatterned Substrates with Self-Responsive Polymer Brushes.

The guiding pattern in the chemoepitaxially directed self-assembly (DSA) of block copolymers is often fabricated by periodically functionalizing homogeneously random copolymer brushes tethered on a substrate. The prepatterned copolymer brushes constitute a soft penetrable surface, and their two components can in principle locally segregate in response to the overlying self-assembly process of block copolymers. To reveal how the self-responsive behavior of the copolymer brushes affects the directing effect, we develop a dissipative particle dynamics model to explicitly include the prepatterned polymer brushes and implement it to simulate the DSA of a cylinder-forming diblock copolymer melt on the sparse pattern of polymer brushes. Through large-scale dynamic simulations, we identify the windows of the content of the random copolymer, the film thickness, and the diameter of the patterned spot, for the formation of perfectly ordered hexagonal patterns composed of perpendicular cylinders. Our dynamic simulations reveal that the random copolymer brushes grafted on the unpatterned area exhibit a remarkable self-responsive ability with respect to the self-assembly of the diblock copolymers overlying them, which may widen the effective window of the content of the random copolymer. Within the processing windows of these key parameters, defect-free patterns are successfully achieved both in simulations and in experiments with sizes as large as a few micrometers for 4-fold density multiplications. This work demonstrates that highly efficient computer simulations based on an effective model can provide helpful guidance for experiments to optimize the critical parameters and even may promote the application of DSA.

Topologically controlled synthesis of active colloidal bipeds

Topological growth control allows to produce a narrow distribution of outgrown colloidal rods with defined and adjustable length. We use an external magnetic field to assemble paramagnetic colloidal spheres into colloidal rods of a chosen length. The rods reside above a metamorphic hexagonal magnetic pattern. The periodic repetition of specific loops of the orientation of an applied external field renders paramagnetic colloidal particles and their assemblies into active bipeds that walk on the pattern. The metamorphic patterns allow the robust and controlled polymerization of single colloids to bipeds of a desired length. The colloids are exposed to this fixed external control loop that causes multiple simultaneous responses: Small bipeds and single colloidal particles interpret the external magnetic loop as an order to walk toward the active zone, where they assemble and polymerize. Outgrown bipeds interpret the same loop as an order to walk away from the active zone. The topological transition occurs solely for the growing biped and nothing is changed in the environment nor in the magnetic control loop. As in many biological systems the decision of a biped that reached its outgrown length to walk away from the reaction site is made internally, not externally.

Spatial resolution improvements with finer-pitch GEMs

Gas Electron Multipliers (GEMs) are used in many particle physics experiments, employing their `standard' configuration with amplification holes of 140 μm pitch in a hexagonal pattern. However, the collection of the charge cloud from the primary ionisation electrons from the drift region of the detector into the GEM holes affects the position information from the initial interacting particle. In this paper, the results from studies with a triple-GEM detector with an X-Y-strip readout anode are presented. It is demonstrated that GEMs with a finer hole pitch of here 90 μm improve the detector's spatial resolution. Within these studies, also the impact of the front-end electronics on the spatial resolution was investigated, which is briefly discussed in the paper.

A DNA robotic switch with regulated autonomous display of cytotoxic ligand nanopatterns

The clustering of death receptors (DRs) at the membrane leads to apoptosis. With the goal of treating tumours, multivalent molecular tools that initiate this mechanism have been developed. However, DRs are also ubiquitously expressed in healthy tissue. Here we present a stimuli-responsive robotic switch nanodevice that can autonomously and selectively turn on the display of cytotoxic ligand patterns in tumour microenvironments. We demonstrate a switchable DNA origami that normally hides six ligands but displays them as a hexagonal pattern 10 nm in diameter once under higher acidity. This can effectively cluster DRs and trigger apoptosis of human breast cancer cells at pH 6.5 while remaining inert at pH 7.4. When administered to mice bearing human breast cancer xenografts, this nanodevice decreased tumour growth by up to 70%. The data demonstrate the feasibility and opportunities for developing ligand pattern switches as a path for targeted treatment.

Coherent control on the generation and annihilation of a pseudospin-induced optical vortex in a honeycomb photonic lattice.

We experimentally investigate the coherently controllable generation and annihilation of a pseudospin-induced optical vortex in an optically induced honeycomb photonic lattice in a Λ-type 85Rb atomic vapor cell. Three Gaussian coupling beams are coupled into the atomic gases to form a hexagonal interference pattern, which can induce a honeycomb photonic lattice under electromagnetically induced transparency. Then, two probe beams interfere with each other to form periodical fringes and cover one set of sublattice in the honeycomb lattice, corresponding to excite the K or K' valleys in momentum space. By properly adjusting the experimental parameters, the generation and annihilation of the induced optical vortex can be effectively controlled. The theoretical simulations based on the Dirac and Schrödinger equations are performed to explore the underlying mechanisms, which will support the observations. The demonstrated properties of such controllable optical vortex may lay the foundation for the design of vortex-based optical devices with multidimensional tunability.

Эволюция транспупиллярной лазерной коагуляции сетчатки в лечении активной ретинопатии недоношенных: от режима одиночного импульса до навигационного сопровождения

Abstract Evolution of transpupillary laser coagulation of the retina in the treatment of active retinopathy of prematurity: from single pulse mode to navigational support A.V. Tereshchenko, I.G. Trifanenkova, Yu.A. Sidorova, V.V. Firsova, V.V. Shaulov S. Fyodorov Eye Microsurgery Federal State Institution, Kaluga branch, Kaluga, Russian Federation K.E. Tsiolkovski Kaluga State University, Kaluga, Russian Federation Purpose. To present the development stages and results of 18 years of experience in laser technologies application for the treatment of premature infants with active ROP in the Kaluga branch of S. Fyodorov Eye Microsurgery Federal State Institution. Material and methods. Transpupillary laser coagulation of the retina (LCR) was performed in 1583 children (2537 eyes) with active ROP for the period from 2004 to 2021. LCR was carried out with various stationary laser ophthalmocoagulators. Stages 2 and 3 of active ROP with an unfavorable disease course, stage of early clinical manifestations, manifestation of aggressive posterior ROP were indications for laser treatment. Results. Transpupillary LCR began to be performed for children with active ROP with a stationary ophthalmic coagulator for the first time in Kaluga branch of the S. Fyodorov Eye Microsurgery in 2004. The technology of patterned LCR in active ROP was applied for the first time at domestic and international clinical practice, in the Kaluga branch of Eye Microsurgery in 2009. Pattern LCR began to be performed on the Integre Pro Scan device in 2016. Pattern with the most dense and uniform arrangement of laser applications – hexagonal – was identified. In 2021 transpupillary LCR of the avascular zone of the retina was performed in automatic mode with navigation support on the Navilas 577s laser system. It was possible to perform LCR of the avascular zone of the retina up to the dentate line in all cases. Regression of disease was achieved in 100% of cases. Conclusion. Evolution of laser technologies and the experience of their use demonstrate the high efficacy, safety and predictability of the results of laser treatment of active ROP. Modern pattern laser techniques are highly effective, safe, dosed and tissue-saving, which can serve as the basis for standardization of retinal laser coagulation technology in the treatment of active ROP. Key words: retinopathy of prematurity, unfavorable type of course, laser coagulation of the retina, hexagonal pattern, navigation system

Effect of infill pattern on the mechanical properties of PLA and ABS specimens prepared by FDM 3D printing

Fused deposition modelling (FDM) is a three-dimensional printing technique which has become more popular and spreading in many fields. In this process, the molten thermoplastic is deposited layer by layer using a heated nozzle. Users can set the infill pattern to save the material and printing time. The main objective of this study is to investigate the tensile properties of polylactic acid (PLA) and Acrylonitrile butadiene styrene (ABS) tensile specimens with different infill patterns such as lines, tri-hexagonal and lightning. Further, the test specimens were prepared as per ASTM D638 using Ender 3D printer with varying infill patterns. The specimens were subjected to tensile tests in a mechanical tensile testing machine. It was observed that the specimens with linear infill patterns obtained higher tensile strength than the tri-hexagonal and lightning pattern infilled specimens. Later on, a microstructural study was examined on the fractured surface using scanning-electron-microscopy (SEM). It shows that the line pattern specimens have more uniform structure when compared to hexagonal and lightning pattern specimens.

Reconstruction of Gold Surface with Excessive Sulfur Source During Transition Metal Disulfide Growth.

The inert gold substrate is one of the most commonly used substrates for synthesizing transition metal dichalcogenides (TMDCs), while the growth mechanism of TMDCs on gold substrates in a sulfur-rich environment is still unclear. Based on density functional theory calculations, we explored the reconstruction of the gold surface in a sulfur-rich environment, which is one of the conditions for the growth of TMDCs. We clearly revealed that both Au(100) and Au(111) surfaces tend to form metal sulfide buffer layers between TMDCs and the metallic substrate, which are the square pattern of Au4S4 on Au(100) surface and the hexagonal pattern of Au6S6 on Au(111) surface, respectively. In the sulfur-rich environment, both square and hexagonal patterns are energetically highly stable, greatly weakening the interaction between TMDCs and the substrate. Interestingly, both buffer layers inherit the symmetry of the substrate and thus have no significant effect on the growth behavior of TMDCs. This study explains many experimental puzzles and elucidates the growth behavior of 2D materials on various substrates.

Enhancing urban safety through honeycomb housing design: A quantitative analysis of crime prevention

Honeycomb housing is a new design within the category of cluster housing that was inspired by the Prairie House concept created by Frank Lloyd Wright between 1900 and 1901. This design uses a hexagonal pattern to form clusters. It presents an alternative to traditional housing layouts, addressing problems like urban overcrowding, high crime rates, and social unrest. Therefore, this research aims to explore how the design of honeycomb housing can contribute to preventing crime and enhancing the safety of urban communities. This is done by examining aspects such as natural surveillance, controlled access, clear boundaries, upkeep, and management. The research adopts a quantitative approach, utilizing surveys completed by 168 heads of households in honeycomb housing, both owners and renters, selected through cluster sampling in Nong Chik Heights, Johor Bahru. The analysis of the data involved descriptive and inferential statistics, including means and standard deviations, frequencies and percentages, and correlation analysis. The findings indicate a positive link between the design of honeycomb housing and crime prevention in urban areas, supported by the principle of maintaining vigilance over public spaces to ensure community safety, tranquility, and protection against external threats.

Nature inspired hexagonal textured patterns using entropy-PROMETHEE-II methods: an experimental study

Nature inspired hexagonal textured patterns using entropy-PROMETHEE-II methods: an experimental study

Designing moiré patterns by strain

Experiments conducted on two-dimensional twisted materials have revealed a plethora of moiré patterns with different forms and shapes. The formation of these patterns is usually attributed to the presence of small strains in the samples, which typically arise during their fabrication. In this paper we find that the superlattice structure of such systems actually depends crucially on the interplay between twist and strain. For systems composed of honeycomb lattices, we show that this can lead to the formation of practically any moiré geometry, even if each lattice is only slightly distorted. As a result, we show that under strain the moiré Brillouin zone is not a stretched irregular hexagon, but rather a primitive cell that changes according to the geometry of the strained moiré vectors. We identify the conditions for the formation of hexagonal moiré patterns arising solely due to shear or biaxial strain, thus opening the possibility of engineering moiré patterns solely by strain. Moreover, we study the electronic properties in such moiré patterns and find that the strain tends to suppress the formation of the flat moiré bands, even in the strain-induced hexagonal patterns analogous to those obtained by the twist only. Our paper explains the plethora of moiré patterns observed in experiments, and provides a solid theoretical foundation from which one can design moiré patterns by strain. Published by the American Physical Society 2024

Synthesis and characterization of graphene oxide, tin oxide, and reduced graphene oxide-tin oxide nanocomposites

The present study reports the synthesis and characterization of graphene oxide (GO), tin oxide nanostructures, and reduced GO (rGO)-tin oxide nanocomposites. The modified Hummer's method was used for the synthesis of GO. Tin oxide nanoparticles were synthesized by co-precipitation method using SnCl2 as tin source. The rGO-tin oxide nanocomposites were synthesized by hydrothermal method using GO and SnCl2 as tin source. The synthesized nanostructures were characterized using powder XRD, FESEM, EDX spectroscopy, TEM, SAED, FTIR spectroscopy, UV–visible spectroscopy, Raman spectroscopy, and TGA. The XRD pattern of the graphite powder shows intense (002) plane peak at 2θ = 26.78° along with the other graphitic XRD peaks. In addition, XRD peaks at 2θ ∼ 14°, 16.8°, 21.18°, and 24.18° were also observed. The characteristic GO (001) plane peak in the XRD pattern could be not be observed in the oxidative exfoliation GO. The Raman spectrum of the graphite powder shows intense crystalline G band, low-intensity defect related D, multi-layered graphitic flake related 2D-band with intensity ratio ID/IG=0.08 and I2D/IG=0.46. The oxidative exfoliated GO shows the degradation of the graphite XRD peaks, but the characteristic GO (001) plane XRD peak could not be observed. The TEM image shows the formation of GO sheets on the oxidative exfoliation of graphite. The d-spacing obtained from the observed hexagonal SAED pattern of the oxidative exfoliated GO was found to be much lower than graphite d-spacing. Raman, UV–visible, FTIR, and TGA studies indicate the formation of GO under oxidative exfoliation of graphite under Hummer’s method. The band gap values of around 1.70 eV from the UV–visible optical absorption also indicates the formation of graphene in the oxidative exfoliated GO. The observed results indicate the formation of graphene embedded amorphous GO.

Effect of Marangoni flow during the solidification of a Fe-0.82wt.%C steel alloy

A two-phase Mixture model is proposed to simulate the liquid-solid phase transition of a Fe-0.82wt%C steel alloy under the effect of Marangoni flow. This model simplifies computations by solving a single momentum and enthalpy equation for the mixture phase using a three-dimensional finite volume method. The simulation involves solidifying a rectangular ingot (100 × 10 × 100 mm3) from the cold bottom surface towards the hot-free surface at the top. To facilitate heat exchange with the surrounding environment, a high heat transfer coefficient of h = 600 W/m2/K was applied on the bottom surface to establish an upward solidification direction. However, a lower heat transfer coefficient of 20 W/m2/K was applied on the top free surface, which was considered flat. This study aims to examine the effect of Marangoni flow generated by surface tension on flow and segregation patterns. The results show that the Marangoni flow emerges at the free surface and penetrates into the liquid depth, leading to the formation of hexagonal patterns along the liquid thickness. Upon full solidification, macro-segregation also exhibits hexagonal structures, mirroring the stationary hexagonal shapes generated by Marangoni flow.

Self-Supervised Joint Learning for pCLE Image Denoising.

Probe-based confocal laser endoscopy (pCLE) has emerged as a powerful tool for disease diagnosis, yet it faces challenges such as the formation of hexagonal patterns in images due to the inherent characteristics of fiber bundles. Recent advancements in deep learning offer promise in image denoising, but the acquisition of clean-noisy image pairs for training networks across all potential scenarios can be prohibitively costly. Few studies have explored training denoising networks on such pairs. Here, we propose an innovative self-supervised denoising method. Our approach integrates noise prediction networks, image quality assessment networks, and denoising networks in a collaborative, jointly trained manner. Compared to prior self-supervised denoising methods, our approach yields superior results on pCLE images and fluorescence microscopy images. In summary, our novel self-supervised denoising technique enhances image quality in pCLE diagnosis by leveraging the synergy of noise prediction, image quality assessment, and denoising networks, surpassing previous methods on both pCLE and fluorescence microscopy images.

Three-dimensional domain identification in a single hexagonal manganite nanocrystal

The three-dimensional domain structure of ferroelectric materials significantly influences their properties. The ferroelectric domain structure of improper multiferroics, such as YMnO3, is driven by a non-ferroelectric order parameter, leading to unique hexagonal vortex patterns and topologically protected domain walls. Characterizing the three-dimensional structure of these domains and domain walls has been elusive, however, due to a lack of suitable imaging techniques. Here, we present a multi-peak Bragg coherent x-ray diffraction imaging determination of the domain structure in single YMnO3 nanocrystals. We resolve two ferroelectric domains separated by a domain wall and confirm that the primary atomic displacements occur along the crystallographic c-axis. Correlation with atomistic simulations confirms the Mexican hat symmetry model of domain formation, identifying two domains with opposite ferroelectric polarization and adjacent trimerization, manifesting in a clockwise arrangement around the hat’s brim.

Negative elastic wave refraction and focusing regulation of single-phase solid phononic crystals

This paper presents the design of a single-phase solid phononic crystal (PnC) structure featuring a regular hexagonal perforation pattern. The structure manifests three negative refraction bands, encompassing one for transverse waves and two for longitudinal waves, thereby enabling simultaneous control of shear and longitudinal waves. Due to the high symmetry of the triangular lattice, the equal frequency curves corresponding to the negative refraction band approach circular shapes, suggesting a nearly isotropic negative refraction effect. This negative refraction effect is achieved through specific mass resonance modes closely related to the porous structure designed in this paper. Initially, we analyze the band structure of the PnC, followed by designing the PnC plate structure to achieve negative refraction control for transverse waves at a frequency of 32.4 kHz, with a negative refraction index of −1. Additionally, negative refraction control for longitudinal waves is attained at frequencies of 44 and 64.54 kHz. Subsequently, we scrutinize the influence of various conditions on negative refraction, including different structural parameters, incident angles, and operating frequencies, while verifying the robustness of the designed phonon crystal structure. Leveraging the negative refraction characteristics of the structure, we construct an elastic wave lens to achieve perfect imaging of shear and longitudinal waves. Finally, employing finite element simulation and analyzing focusing imaging characteristics with different source positions, we validate that the results closely align with theoretical expectations. The solid PnC structure designed in this study holds significant potential for applications in the fields of elastic wave imaging.

Apparent Modulus of Honeycomb Structure: A Guideline for Porous Structure Implant Design

Objectives: To investigated the apparent modulus of honeycomb to be used as a guideline for facilitating porous structure implant design. Methods: Apparent modulus of each honeycomb model was developed based on finite element analysis. Geometry of honeycomb structures included circumcircle radius of 2 mm, 3 mm, and 4 mm with wall high of 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm. Results: Hexagonal shape of honeycomb structure with circumcircle radius 2 mm was compared with circle with 2 mm diameter, both with wall thickness of 1 mm. The relationship is beset described by logarithm equation with coefficient of correlation above 0.99. It was found that reduction of modulus for circular shape is 60 percents. The value is greater than hexagonal pattern which is 50 percents of reduction. Conclusions: The relationship between height of honeycomb and reduction of apparent modulus of each specific circumcircle radius of honeycomb is beset described in logarithm equation and as a guideline for facilitating porous structure implant design.

Emergence of a hexagonal pattern in shear-thickening suspensions under orbital oscillations

A dense particle suspension under shear may lose its uniform state to large local density and stress fluctuations, which challenge the mean-field description of the system. Here, we explore the novel dynamics of a non-Brownian suspension under orbital oscillations, where localized density waves along the flow direction appear beyond an excitation frequency threshold and self-organize into a hexagonal pattern across the system. The spontaneous occurrence of the inhomogeneity pattern arises from a coupling between particle advection and the shear-thickening nature of the suspension. Through linear stability analysis, we show that they overcome the stabilizing effects of particle pressure at sufficient particle volume fraction and oscillation frequency. In addition, the long-standing density waves degenerate into random fluctuations when replacing the free surface with rigid confinement. It indicates that the shear-thickened state is intrinsically heterogeneous, and the boundary conditions are crucial for developing local disturbance.

A DNA origami device spatially controls CD95 signalling to induce immune tolerance in rheumatoid arthritis.

DNA origami is capable of spatially organizing molecules into sophisticated geometric patterns with nanometric precision. Here we describe a reconfigurable, two-dimensional DNA origami with geometrically patterned CD95 ligands that regulates immune cell signalling to alleviate rheumatoid arthritis. In response to pH changes, the device reversibly transforms from a closed to an open configuration, displaying a hexagonal pattern of CD95 ligands with ~10 nm intermolecular spacing, precisely mirroring the spatial arrangement of CD95 receptor clusters on the surface of immune cells. In a collagen-induced arthritis mouse model, DNA origami elicits robust and selective activation of CD95 death-inducing signalling in activated immune cells located in inflamed synovial tissues. Such localized immune tolerance ameliorates joint damage with no noticeable side effects. This device allows for the precise spatial control of cellular signalling, expanding our understanding of ligand-receptor interactions and is a promising platform for the development of pharmacological interventions targeting these interactions.

Tin oxide thin films on Ag(111): Thickness and temperature dependent study of surface structure and electronic properties

Growth and structure of tin oxide films on Ag(111) from submonolayer to 10 monolayer equivalent thickness have been studied using low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS) and angle-resolved photoemission spectroscopy techniques for room temperature (RT) and high temperature (HT) (573 K). For RT growth, most of the tin is oxidised to form tin oxide (SnOx) as confirmed by XPS where no metallic component is noticed. However, the grown films are not epitaxial or ordered which can be confirmed by no spots in LEED for higher coverage. Metallic Sn along with two oxidation states of Sn are noticed for HT growth, with the surface mainly composed of SnO2. LEED pattern shows the presence of c(2 × 2) and (3 × 1) along with two different hexagonal multidomain type patterns. The electronic structure for lower coverage resembled the Sn/Ag(111) alloy structures for lower coverage. For higher coverages appearance of three bands below 2 eV binding energy was noticed.