Bent Structure Research Articles

Molecular Structures of Surfaces and Interfaces of Poly(dimethylsiloxane) Incorporated with Silicone Oils Containing Phenyl Functionality.

Poly(dimethylsiloxane) (PDMS) materials have been widely researched and applied as fouling-release coatings. Incorporation of silicone oils into PDMS has been shown to improve the antifouling properties of PDMS materials. In this research, we applied sum frequency generation (SFG) vibrational spectroscopy to study PDMS materials incorporated with various silicone oils containing phenyl groups in air, water, and protein solutions. It was found that the surface structures of various silicone oils varied, which results in different surface structures of PDMS with different oils incorporated. Such different PDMS surfaces interact with water molecules differently, leading to different surface hydrations. A model protein, fibrinogen, was used to study molecular interactions between oil-incorporated PDMS and biological molecules, testing the antifouling and fouling-release performance of different PDMS materials. It was found that fibrinogen has different adsorption behaviors on different PDMS surfaces, while adsorbed fibrinogen adopts bent structures. This study demonstrated that SFG can be used to deduce molecular information on silicone oil, PDMS, water, and fibrinogen on surfaces/at interfaces in situ in real-time. The different silicone oils incorporated into PDMS changed the PDMS surfaces, leading to varied interactions with water and biological media, influencing the antifouling and fouling-release activities. In most cases, the presence of silicone oils could enhance the surface hydration. However, the presence of phenyl groups could reduce the level of surface hydration. Nevertheless, our studies demonstrated that incorporation of silicone oils into PDMS led to better antifouling or fouling-release properties.

Regioisomeric π-Extended Nanographene with Long-Lived Phosphorescence Afterglow.

The cutouts of graphene sheets, particularly those with a nonplanar topology, present vast opportunities for advancement. Even a slight deviation from the planar structure can lead to intriguing (chiro)optical features for helically twisted nanographenes. In this context, we introduce two regioisomeric π-extended nanographenes that exhibit distinct excited-state characteristics. The helicene structure and the photophysical features can be easily tuned by changing the connecting position of the nanographene to the carbazole core (2,7- and 3,6-). Single-crystal X-ray diffraction analysis confirmed the formation of nanographenes with bent and helical conformations. Both derivatives exhibited thermally activated delayed fluorescence at room temperature and phosphorescence at low temperatures. Notably, the nanographene with the bent structure displayed an impressive red afterglow lasting over 30 seconds, in contrast to the very weak afterglow observed in the helical structure. DFT calculations revealed the existence of an isoenergetic higher triplet state (T8) and comparatively weak spin-orbit coupling (T1-S0), thereby enabling the bent nanographene to exhibit a long-lived component and strong afterglow. Our findings highlight the significance of regioisomeric nanographenes with exceptional optical properties and offer a deeper understanding of the structure-property relationship in nonplanar nanographenes.

Isolation and Structure Elucidation of the Heterocumulene Anions [NCC-L]- (L = CO, CS, N2).

Cumulenes are molecules characterized by a series of consecutive double bonds. They serve as important reagents and intermediates in the synthesis of polymers and a wide variety of functionalized compounds, including various heterocycles. Understanding the properties of cumulenes and developing synthetic routes to these often highly reactive species is essential for unlocking new applications. Here, we report the synthesis and isolation of the cyanodiazomethanide [NCCNN]- and cyanothioketenyl anion [NCCCS]-. These 5-atomic anions exhibit unexpected stabilities but distinct structural differences. Despite the explosive nature of diazoacetonitrile, the [NCCNN]- anion was sufficiently stable at 0 °C to allow for first reactivity studies and its structure elucidation revealing a bent structure. The thioketenyl anion is stable at room-temperature and can be accessed from the cyanoketenyl anion [NCCCO]- via a [2+2] cycloaddition and cycloreversion sequence with COS elimination. Comparative structural, spectroscopic and computational studies including those on the cyanoketenyl anion [NCCCO]-, demonstrate that the degree of bending of these heterocumulene anions [NCC-L]- can be explained by a transition in the bonding situation from a cumulene structure to an anionic carbone, with the strongly π accepting CS ligand leading to a linear structure of the thioketenyl anion.

Low-coordinate bis-phosphine and monophosphine Ni(0) complexes: synthesis and reactivity in C-S cross-coupling.

Preformed Ni(0) complexes are rarely used as precatalysts in cross-coupling reactions, although they can incorporate catalytically active nickel directly into the reaction. In this work, we focus on the preparation and the catalytic application of low-coordinate Ni(0) complexes supported by bulky monophosphine ligands in C-S cross-coupling reactions. We have prepared two families of Ni(0) complexes, bis-phosphine aducts of the type [Ni(PR2Ar')2] (Ar' = m-terphenyl group) and monophosphine derivatives of the type [Ni(PR2Ar')(DVDS)] (DVDS = divinyltetramethyldisiloxane). DFT calculations were used to account for the atypical bent structures displayed by the bis-phosphine Ni(0) complexes. Monophosphine-Ni(0) complexes display catalytic activity superior to bis-phosphine Ni(0) adducts, which suggests that the former facilitate the generation of highly reactive monoligated PNi(0) species. Furthermore, the reactivity of monophosphine-Ni(0) precatalysts outperform that observed with Ni(II) precatalysts with the same phosphine ligands, supporting a more facile activation step to the same catalytic species. This enhanced reactivity allows for the use of lower catalyst loadings (1-5 mol%) and for carrying out the challenging coupling between aryl chlorides and alkylthiols.

Probing mechanical selection in diverse eukaryotic genomes through accurate prediction of 3D DNA mechanics.

Connections between the mechanical properties of DNA and biological functions have been speculative due to the lack of methods to measure or predict DNA mechanics at scale. Recently, a proxy for DNA mechanics, cyclizability, was measured by loop-seq and enabled genome-scale investigation of DNA mechanics. Here, we use this dataset to build a computational model predicting bias-corrected intrinsic cyclizability, with near-perfect accuracy, solely based on DNA sequence. Further, the model predicts intrinsic bending direction in 3D space. Using this tool, we aimed to probe mechanical selection - that is, the evolutionary selection of DNA sequence based on its mechanical properties - in diverse circumstances. First, we found that the intrinsic bend direction of DNA sequences correlated with the observed bending in known protein-DNA complex structures, suggesting that many proteins co-evolved with their DNA partners to capture DNA in its intrinsically preferred bent conformation. We then applied our model to large-scale yeast population genetics data and showed that centromere DNA element II, whose consensus sequence is unknown, leaving its sequence-specific role unclear, is under mechanical selection to increase the stability of inner-kinetochore structure and to facilitate centromeric histone recruitment. Finally, in silico evolution under strong mechanical selection discovered hallucinated sequences with cyclizability values so extreme that they required experimental validation, yet, found in nature in the densely packed mitochondrial(mt) DNA of Namystynia karyoxenos, an ocean-dwelling protist with extreme mitochondrial gene fragmentation. The need to transmit an extraordinarily large amount of mtDNA, estimated to be > 600 Mb, in combination with the absence of mtDNA compaction proteins may have pushed mechanical selection to the extreme. Similarly extreme DNA mechanics are observed in bird microchromosomes, although the functional consequence is not yet clear. The discovery of eccentric DNA mechanics in unrelated unicellular and multicellular eukaryotes suggests that we can predict extreme natural biology which can arise through strong selection. Our methods offer a way to study the biological functions of DNA mechanics in any genome and to engineer DNA sequences with desired mechanical properties.

Trends in Methanol-Solvated Actinide Ions and Actinide Expanded Porphyrin Complexes.

Trivalent actinide expanded porphyrin complexes have been of synthetic interest since the isolation of the series of trivalent lanthanide texaphyrin complexes in 1992, however, synthesis of these actinide-based complexes has not yet been achieved. In this work, a computational study with relativistic density functional theory was performed to determine how trivalent actinide ions (Ac3+ through Lr3+) interact with Schiff base expanded porphyrin macrocycles in a methanol solvent as an alternate pathway to stabilization. A thorough analysis of structural parameters, electronic structure, stability of microsolvation environments, and relative binding energies provided insight into the most stable structures. Trends in bonding and structure for the full actinide series are reported for methanol solvated ions, which reports actinide contraction along the series for early and mid actinides. Texaphyrin incorporates the actinide ions in a planar fashion, whereas for alaskphyrin a bent structure is more favorable; this bend results in stronger interaction energies than those calculated for the texaphyrin complexes. We also show that the redox-active expanded porphyrin ligands are able to accommodate a variety of actinides through charge transfer stabilization. Based on relative binding energy and energy decomposition analysis, it was found that texaphyrin and alaskaphyrin both exhibit a strong preference for binding to Th.

Influence of Structural Parameters on the Mechanical Performance of Multi-Layer U-Shaped Metal Bellows

Metal bellows feature a simple structure, high-temperature resistance, corrosion resistance, and strong flexibility for compensation, making them widely used in the aerospace, machinery, and petrochemical industries. Compared to multilayer bellows, single-layer bellows are simpler in structure and forming process, making the performance easier to achieve. The structural parameters of multilayer metal bellows, particularly the number of layers, significantly impact the performance. This study focuses on multilayer U-shaped metal bellows made of 304 stainless steel. Using ABAQUS finite element software, a full simulation of the hydroforming and performance analysis of multilayer U-shaped metal bellows is conducted. This study examines the effects of wall thickness thinning and residual stress distribution caused by hydroforming and explores how structural parameters (including outer diameter, corrugation height, corrugation spacing, and wall thickness) influence axial stiffness and bending performance. The findings provide valuable insights for the design and selection of metal bellows.

Trial Design of a Truss Bridge Prefabricated Using a Rectangular Steel Tube—Ultra-High-Performance Concrete Composite

In order to promote the development of bridge assembly technology and accelerate the application of rectangular steel-tube–concrete composite truss bridges, this study focuses on the Yellow River Diversion Jiqing Main Canal Bridge as the engineering example and conducts a numerical analysis of a rectangular steel-tube–concrete composite truss bridge. Based on the results of the analysis, structural optimization is achieved in three dimensions—structural design, construction methods, and force analysis—leading to the establishment of key design parameters for through-type ultra-high-performance rectangular steel-tube–concrete composite truss bridges. The results show that filling the hollow sections with ultra-high-strength concrete can significantly enhance the load-bearing capacity. Additionally, employing prestressed concrete components addresses the bending and tensile load capacity challenges of composite structures, thus maximizing the material strength advantages. The proposed preliminary design scheme incorporates prestressed PBL-reinforced tie rods filled with ultra-high-performance concrete with optimal design parameters, such as high span ratios, wide span ratios, and ideal segment lengths, are suggested to ensure that the strength, stiffness, and stability comply with relevant standards. While ensuring that the structure meets safety, applicability, and durability criteria, the preliminary design scheme reduces steel usage by 23.5%, concrete usage by 11.6%, and overall costs by 17.29% compared to the original design. The proposed design demonstrates distinct advantages over the original in terms of mechanical performance, construction efficiency, economic viability, and durability, highlighting its promising application potential.

Structural performance of additive manufactured wood-sodium silicate composite beams for sustainable construction

The current research examines the structural bending performance of additive manufactured wood-sodium silicate composite beams of various span-to-height proportions. Beams consisting of both a single layer as well as two layers of extruded wood-sodium silicate composite were considered. Both groups of beams exhibited a rise in maximum shear force (Vmax), maximum bending moment (Mmax), apparent modulus of elasticity (MOEapp), and modulus of rupture (MOR) when the span-to-height proportions rose. However, the amount of shear stress (τmax) decreased as the span-to-height proportion increased. Furthermore, the flexural and shear stress patterns for span-to-height proportions of 6 and 30 were calculated analytically using the transformed section methodology across the thickness of the beams at different positions of L/6, L/3, 5L/12, and L/2 of the beam span. The results demonstrated that the bending stress increased as the distances from the supports increased toward the middle of the beam. Compared to single-layer beams, two-layer beams displayed lower stress values overall. In particular, the bending stress was 4.85% lower in the two-layer beam with a span-to-height proportion of 6 than that of the single-layer beams. Furthermore, the single-layer beam's maximum shear stress was slightly greater than the two-layer beams. The greatest shear stress of the single-layer beams were computed 4.27% and 0.46% higher than those of the two-layer beams at span-to-height proportions of 6 and 30, respectively.

Self-Powered, Flexible, Wireless and Intelligent Human Health Management System Based on Natural Recyclable Materials.

Combining wearable sensors with modern technologies such as internet of things and big data to monitor or intervene in obesity-induced chronic diseases, such as obstructive sleep apnea, type II diabetes, cardiovascular diseases, and Alzheimer's disease, is of great significance to the self-health management of human beings. This study designed a loofah-conducting graphite four friction layer enhanced triboelectric nanogenerator (LG-TENG) and developed a health management system for human motion recognition and early warning of sleep breathing abnormalities. By uniformly spraying and depositing conductive graphite on the surface of the loofah and the elastic film cross-interlocking bending structure design, the signal strength of the LG-TENG has been improved by 390%. The stable output signal is still maintained after 1500 s of continuous operation at a frequency of 2 Hz. LG-TENG can realize accurate motion analysis by muscle contraction state. Combining different deep learning models resulted in 98.1% accuracy in recognizing seven categories of displacement speeds for an individual and 96.46% accuracy in recognizing seven categories of displacement speeds for three individuals. In addition, the sleep breathing monitoring early warning system was developed by integrating Bluetooth wireless transmission and upper computer analysis technology. This system aims to analyze and provide real-time warnings for sleep-breathing abnormalities. This research promotes an innovation of TENG technology based on the advantages of natural materials, recyclability and low cost. It offers new ideas for self-health management and scientific exercise for obese people, showing a broad application prospect.

Revealing the Effect of Curvature Structure in Hard Carbon Anodes for Lithium/Sodium Ion Batteries.

Heteroatom doping is the most common means to enhance the Li+/Na+ ions storage of hard carbon (HC). The explanation of the storage mechanism of heteroatom-doped HC is to increase the active site or widen the layer spacing while ignoring the effect of local bending structure induced by it. Meanwhile, the storage mechanism by the localized bending structure also lacks in-depth study. Herein, a locally curved configuration and an amorphous structure are designed by introducing different heteroatoms, respectively, and the mechanism of the two types of structures on the Li+/Na+ ions storage is explored. The density functional theory (DFT) calculation shows that the adsorption energy of Li+/Na+ ions is optimal at the appropriate curvature of 27.72 m-1. Serving as anode for lithium/sodium ion batteries in ester electrolytes, the optimized HCs demonstrate satisfied specific capacity and high-rate capability, respectively. Furthermore, the charging capacity below 1.0V of HC with suitable curvature microstructure reaches 84.8% and 90.1% of the total charge capacity, confirming that the curvature defects can better control the delithiation/desodiation process, and provide a higher energy density. This study enlightens new insights into the storage mechanisms of Li+/Na+ ions and provides guidance for better design of heteroatom-doped carbon anodes with superior performance.

Polarization-selective metamaterial absorber using tailored Y-shaped SRR for UWB device and Doppler navigation aids applications

In this paper, we present an unprecedented metamaterial absorber design exhibiting exceptional characteristics in electromagnetic wave absorption. The proposed bent Y-shaped structure, fabricated on an FR-4 substrate with copper patches, showcases remarkable performance across a diverse frequency spectrum. Through exhaustive simulations in CST, this design manifests eight distinct resonant frequencies, achieving absorption rates exceeding 90 % at each resonance. The resonances, strategically spanning from L-band (3.728 GHz) through S-band, C-band, X-band, Ku-band, and K-band up to 22.664 GHz, signify unparalleled versatility and efficacy in mitigating electromagnetic radiation. It investigates the equivalent circuit parameters of a proposed metamaterial absorber design, focusing on inductance (L), capacitance (C), and resistance (R). This paper investigates the applications of UWB devices at 3.728 GHz and Doppler navigation aids at the 13.4 GHz frequency as regulated by the Federal Communications Commission. It includes a discussion on near-zero refractive Index Metamaterials (NZRIM), highlighting their potential utilization in achieving extraordinary control over wave behaviour. Notably, the absorber's inherent polarization insensitivity fortifies its adaptability in various applications. Additionally, the metamaterial exhibits near-zero or negative permittivity, altering electric response, while simultaneously demonstrating permeability absolute zero throughout all frequency bands sparking new avenues for exploration and challenging conventional electromagnetic theories.

Multi-scale finite element analysis of laser-assisted forming of CF/PEEK composite corner structures

Laser-assisted forming can significantly increase the forming efficiency of thermoplastic composites. However, when forming CF/PEEK curved corner structures using laser-assisted forming, bending spring-back generated by the prepreg tape constrains the shape accuracy of the component. The bending deformation of unidirectional resin matrix composite materials is highly nonlinear. In this study, a multi-scale finite element method is used to obtain the bending properties of CF/PEEK composites for bending spring-back phenomenon of thermoplastic composite samples and predict the spring-back angle of CF/PEEK corner structures fabricated via laser-assisted forming. The average material properties were first calculated using RVE. Following this, a mesoscale model was developed to analyze kink deformation of the composite. Finally, the macroscopic prepreg bending spring-back was calculated. It was determined that the main mechanism of corner forming corresponds to the occurrence of a fiber kinking phenomenon on the interior of the corner. Furthermore, spring-back deformation is caused by residual stresses resulting from insufficient fiber kinking. The accuracy of the simulation results is verified via corner forming experiments. This study contributes to a deeper understanding of the spring-back mechanisms of laser-assisted forming of corner structures and provides a theoretical guidance for precision forming of multilayer thermoplastic composite bent structures.

Biomimetic hair-assisted GaN optical devices for bidirectional airflow detection

Airflow sensing plays a pivotal role in numerous fields, including medicine, industry, and environmental monitoring. However, detecting bidirectional airflow using a single sensing unit poses significant challenges. In this work, a miniature airflow sensing device is introduced, utilizing a GaN optical chip integrated with a biomimetic hair structure. The sensing device comprises a monolithic GaN chip that handles both light emission and detection. The biomimetic hairs, constructed from nylon fibers and PDMS film, undergo structural bending in converting airflow signals into optical changes, modulating the light captured by the on-chip detector. The intensity of the airflow directly correlates with the bending extent of the biomimetic hair, facilitating the precise detection of airflow rates through changes in the photocurrent. The integrated device can measure a wide range of airflow rates from −23.87 ms−1 to 21.29 ms−1, and exhibit a rapid response time of 13 ms and a detection limit of 0.1 ms−1. Characterized by its compact size, fast response time, and bidirectional detection ability, the developed device holds immense potential for applications in breath detection, speech recognition, encoding information, and the realization of logic operations.

Comparative Analysis of FSW and SFSW Welded Joints of EN AW 1200 Aluminum Alloy

Friction stir welding is a research direction within ISIM Timisoara, with contributions and results obtained in several research projects carried out in this field. The paper presents results obtained by ISIM Timisoara regarding FSW welding in ambient environment and in liquid working environment (submerged friction stir welding SFSW) of EN AW 1200 aluminum alloy, using a welding tool made of steel, with threaded cylindrical pin. FSW welding in liquid working environment aims to avoid overheating of the welding tool and welding device during the joining process, as well as achieving better results compared to FSW welding in ambient environment. The evaluation of welded joints included structural analysis, hardness measurements, tensile and bending tests. A comparative analysis of the results obtained in the FSW / SFSW welding experiments carried out for the EN AW 1200 aluminum alloy is presented. The obtained results are useful for the outline of the future experimental research programs which will be carried out within the ongoing Nucleu project PN 23.37.01.02, regarding friction stir processing in ambient and in a liquid environment of this material.

Slip-mediated axisymmetric bending of multilayered structures with different interfaces: Analytical solutions and design guidelines

Multilayered structures with slippery interfaces exhibit significant interlayer sliding during bending, enabling the design of structures with integrated functional capabilities by tailoring interfacial properties to control slip behavior and overall bending response. This study investigates the influence of different interfacial slip behaviors on the axisymmetric bending of multilayered structures, deriving analytical solutions for deflection and stiffness under two key interfacial shearing laws: Elastic Shear Stress (ESS) and Critical Shear Flow (CSF). The analytical results, validated by Finite Element Method (FEM), elucidate the impact of different shearing models on interfacial slip and overall load-displacement bending response. This study not only establishes a theoretical framework for understanding and predicting the bending behavior of circular multilayered structures with interfacial slip, but also provides valuable insights for experimental measurements and the design of functionally integrated structures.

Hydrogen Bond‐Induced Flexible and Twisted Self‐Assembly of Functionalized Carbon Dots with Customized‐Color Circularly Polarized Luminescence

AbstractCircularly polarized luminescence (CPL) has numerous applications in optical data storage, quantum computing, bioresponsive imaging, liquid crystal displays, and backlights in three‐dimensional (3D) displays. In addition to their competitive optical properties, carbon dots (CDs) benefit from simple and low‐cost preparation, facile post‐modification, and excellent resistance to photo‐ and chemical bleaching after carbonization. Combining the superior optical performance with polarization peculiarities through hierarchical structure engineering is imperative for the development of CDs. In this study, hydrophobic interactions of aromatic ligands, which participate in the surface‐ligand post‐modification process on the ground‐state chiral carbon core, are employed to drive the oriented assembly. Furthermore, the residual chiral amides on CDs form multiple hydrogen bonds during gradual aggregation, causing the assembled materials to form an asymmetric bending structure. Superficial ligands interfere with the optical dynamics of the exciton radiation transition and stabilize the excited state of the assembled materials to achieve a circularly polarized signal. The linkage ligands overcome the frequent aggregation‐induced quenching phenomenon that present difficulties in conventional CDs, facilitate the assembly of self‐supporting films, and improve chiral optical expression. The full‐color and white CPL are manipulated by simply adjusting the functional groups of the ligands, which also illustrates the versatility of the post‐modification strategy. Finally, large chiral flexible films and multicolor chiral light‐emitting diodes based on the stable chiral powder phosphors were constructed, thereby providing feasible materials and technical support for flexible 3D displays.

Direct laser writing of curved SERS for light-guided enhancement

Flexible SERS substrates, typically used on irregular surfaces, have unexplored optomechanical effects that could enhance performance. We developed a micromechanically bending structure, i.e. microbender, to study how bending affects SERS substrates’ performance. Optical simulations of nanopillar arrays on micro-curved surfaces showed a 25–134 % improvement in mean-field localization at the pillar tips for arrays with pillar diameters of 0.4–1 μm, pitches of 0.5–0.8 μm, and heights of 0.5–4.5 μm. Raman measurements showed that SERS intensity increases when in a curved state due to enhanced light scattering, guiding, and field localization. A curved array of 6 μm tall pillars (0.5 μm diameter, 1 μm spacing) produced Raman intensities similar to dense single-voxel arrays with shorter 0.8 μm pillars (0.2 μm diameter, 0.2 μm gaps) in the planar state. This finding suggests that low resolution fabrication technologies can produce curved SERS substrates with similar performance to high resolution planar SERS, offering an alternative to the current “smaller is better” trend through post-fabrication manipulation.

Finite element methods for the stretching and bending of thin structures with folding

Finite element methods for the stretching and bending of thin structures with folding

Shrinkage and deformation of material extrusion 3D printed parts during sintering: Numerical simulation and experimental validation

Material extrusion 3D printing (ME3DP) combined with sintering is a low-cost additive manufacturing technique for fabricating components of difficult-to-print metals, such as copper, aluminum, and ceramics. However, the sintering process includes complex material science, such as volumetric shrinkage and free structural bending, to identify the relative density and deformation of a 3D printed sample. The prediction of the relative density and deformations during the sintering process provides information to the design engineer to optimize the design of the CAD model before sintering. In this study, a phenomenological model based on constitutive equations was developed to predict the density and structural deformation during the sintering process of pure copper components fabricated by ME3DP using metal injection molding feedstock. The densification rate was determined using shrinkage estimation with an isothermal stairway heating cycle in a vertical dilatometer. Furthermore, different sets of experiments were performed with a load on the probe with long isothermal heating cycles at 850, 900, 950, 1000, and 1050 °C in a vertical dilatometer to estimate the axial viscosity of the copper. The constitutive equations were solved using the solid mechanics module with user-defined creep in COMSOL Multiphysics by considering isotropic assumptions. Two types of geometries, cube and overhanging I section, were used to predict shrinkage and deformation during the sintering process. The developed model successfully predicted the relative density based on shrinkage and structural deformation owing to gravity during the sintering process.