Optical Microscopy Research Articles

Influence of Process Parameter and Build Rate Variations on Defect Formation in Laser Powder Bed Fusion SS316L.

Laser powder bed fusion (LPBF) is an additive manufacturing process that has gained interest for its material fabrication due to multiple advantages, such as the ability to print parts with small feature sizes, good mechanical properties, reduced material waste, etc. However, variations in the key process parameters in LPBF may result in the instantiation of porosity defects and variation in build rate. Particularly, volumetric energy density (VED) is a variable that encapsulates a number of those parameters and represents the amount of energy input from the laser source to the feedstock. VED has been traditionally used to inform the quality of the printed part but different values of VED are presented as optimal values for certain material systems. An optimal VED value can be maintained by changing the key process parameters so that various combinations yield a constant value. In this study, an optimal constant VED value is maintained while printing SS316L with variable key processing parameters. Porosity analysis is performed using optical microscopy, as well as X-ray computed tomography, to reveal the volume density and distribution of those pores. Two primary defect categories are identified, namely lack of fusion and porosity induced by balling defects. The findings indicate that, even at optimal VED, variations in process parameters can significantly influence defect type, underscoring the sensitivity of defect formation to the variation of these parameters. Furthermore, a minor change in the build rate, driven by adjustments in process parameters, was found to influence defect categories. These findings emphasize that fine tuning the process parameters and build rate is essential to minimize defects. Finally, fiducial marks have been identified as a source of unintentional porosity defects. These results enable the refinement of process parameters, ultimately optimizing LPBF to achieve enhanced material density and expedite the printing.

Hierarchically Structured Stimuli-Responsive Liquid Crystalline Terpolymer-Rhodamine Dye Conjugates.

Optically responsive materials are applied in sensing, actuators, and optical devices. One such class of material is dye-doped liquid crystal polymers that self-assemble into cholesteric mesophases that reflect visible light. We report here the synthesis and characterization of a family of linear and mildly crosslinked terpolymers prepared by the ROMP of norbornene-based monomers. The three monomers were composed of (i) rhodamine dye through one or two norbornene end groups utilizing flexible C10-alkane spacers, (ii) a cholesteryl liquid crystal (LC) using C9-alkane spacers, and (iii) PEG side chains. We investigated how these architectural variations in these terpolymers impacted their hierarchically self-assembled mesophase properties. We probed their composition, morphology, thermal, mechanic, photochromic, and mechanochromic properties using, inter alia, 1H NMR spectroscopy, DSC, temperature-dependent SAXS, diffuse reflectance UV-vis spectroscopy, and optical polarization microscopy. The new terpolymers exhibited architecture-dependent thermochromic, mechanochromic, and piezochromic properties arising from LC-rhodamine dye interactions. We found that a compromise between the rigidity and flexibility of the terpolymer architectures needed to be stricken to fully express stimuli-responsive properties. These terpolymers also showed distinctly different properties compared to those of a previously reported structurally related liquid crystalline copolymer made from two monomers. These findings help to define the design principles for optimally stimuli-responsive liquid crystalline polymers.

The impact of graphene oxide nanoparticles on the migratory behavior of metastatic human breast cancer cell, MDA-MB-231.

Breast cancer (BC) with aggressive metastasis is a serious ongoing public health problem among women. Graphene oxide (GO) has an inhibitory effect on the migration rate and metastasis of BC cells, but its various aspects have not yet been explored. This paper aims to research into the effect of GO nanoparticles (GO-Np) on the migratory behavior of MDA-MB-231 as a metastatic human BC cell line. We synthesized GO-Np using a modified Hummer's method. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and zeta potential analyses were conducted to characterize GO-Np. Cytotoxicity of GO-Np against MDA-MB-231 cell lines was examined by optical microscopy and DAPI staining. Migration of cancer cells was analyzed by scratch healing test. Finally, the impact of GO-Np on the expression of BC markers, including Thrombospondin1 (THBS1) and Fibronectin1 (FN1) was investigated by Immunocytochemistry assay (ICC). Results showed a dose-dependent cytotoxicity of GO-Np to MDA-MB-231 cells. The half-maximal inhibitory concentration (IC50) of GO-Np was about 40 μg/ml based on both DAPI test and optical microscopy. The scratch healing test at IC50 concentration of GO-Np, showed a significant decrease (24.4%) in the migration percentage of cells compared to untreated cells. The ICC assay indicated that GO-Np can suppress the expression of both THBS1 and FN1, proving its anti-metastatic properties. In conclusion, GO-Np showed a promising anti-metastatic effect in MDA-MB-231 BC cells.

Hot deformation behavior study and constitutive modeling of Ferrium® C64 carburizing steel

The hot deformation behavior of Ferrium® C64 (Fe-16Co-7.5Ni-0.1C) alloy was studied using isothermal uniaxial hot compression tests (HCT) from 1123K to 1423K and strain rates of 0.01 to 10 s−1. The Arrhenius hyperbolic sine law modeled the flow behavior with an R² of 0.99. Material constants and a deformation activation energy of 488 ± 23 kJ/mol at peak stress were determined. Microstructure using optical microscopy and EBSD analysis and phase identification using XRD were conducted. Flow stress analysis revealed strain hardening at low temperatures/high strain rates and dynamic recrystallization (DRX) at high temperatures/slow strain rates. The strain rate sensitivity map showed positive strain rate sensitivity (m) over the investigated domain and optimal processing parameters for hot working is recommended.

Patterning and nanoribbon formation in graphene by hot punching

Large area graphene patterning is critical for applications. Current graphene patterning techniques, such as electron beam lithography and nano imprint lithography, are time consuming and can scale unfavorably with sample size. Resist-based masking and subsequent dry plasma etching can lead to high roughness edges with no alignment to the underlying graphene crystal orientations. In this study, we present hot punching as a novel and feasible method for patterning of chemical vapor deposition (CVD) graphene sheets supported by a polyvinylalcohol (PVA) layer. Additionally, we observe the effect of such hot punching on graphene supported by PVA via optical microscopy, Raman spectroscopy, AFM, and TEM, including wrinkling, strain and the formation of nanoribbons with crystallographically aligned and smooth edges due to fracturing. We present hot punching as a facile technique for the production of arrays of such nanoribbons.

The influence of a comb-like polymer functionalized phosphate ionic liquid as a lubricant additive on micropitting

In this study, a comb-like polymer functionalized phosphate ionic liquid was synthesized and tested for its effectiveness in reducing friction and wear, as well as its capability to prevent micropitting in PAO base oil using SRV and MPR. It outperforms commercially available phosphate ionic liquids. The wear surface characteristics were analyzed using optical and electron microscopy, and changes in compound structure on the wear surface were studied using XPS spectroscopy. Through a combination of experimental observations and theoretical analysis, it is suggested that the lubrication mechanism is attributed to a synergistic effect between a “soft film” containing comb-like polymers formed through the adsorption of the ionic liquid, and a tribofilm consisting of phosphate compounds and a nitrogen-containing organic matrix.

System- and sample-agnostic isotropic three-dimensional microscopy by weakly physics-informed, domain-shift-resistant axial deblurring

Three-dimensional subcellular imaging is essential for biomedical research, but the diffraction limit of optical microscopy compromises axial resolution, hindering accurate three-dimensional structural analysis. This challenge is particularly pronounced in label-free imaging of thick, heterogeneous tissues, where assumptions about data distribution (e.g. sparsity, label-specific distribution, and lateral-axial similarity) and system priors (e.g. independent and identically distributed noise and linear shift-invariant point-spread functions are often invalid. Here, we introduce SSAI-3D, a weakly physics-informed, domain-shift-resistant framework for robust isotropic three-dimensional imaging. SSAI-3D enables robust axial deblurring by generating a diverse, noise-resilient, sample-informed training dataset and sparsely fine-tuning a large pre-trained blind deblurring network. SSAI-3D is applied to label-free nonlinear imaging of living organoids, freshly excised human endometrium tissue, and mouse whisker pads, and further validated in publicly available ground-truth-paired experimental datasets of three-dimensional heterogeneous biological tissues with unknown blurring and noise across different microscopy systems.

Significance of Tool Coating Properties and Compacted Graphite Iron Microstructure for Tool Selection in Extreme Machining.

This study aims to determine the extent to which coating composition and workpiece properties impact machinability and tool selection when turning Compacted Graphite Iron (CGI) under extreme roughing conditions. Two CGI workpieces, differing in pearlite content and graphite nodularity, were machined at a cutting speed of 180 m/min, feed rate of 0.18 mm/rev, and depth of cut of 3 mm. To assess the impact of tool properties across a wide range of commercially available tools, four diverse multilayered cemented carbide tools were evaluated: Tool A and Tool B with a thin AlTiSiN PVD coating, Tool C with a thick Al2O3-TiCN CVD coating, and Tool D with a thin Al2O3-TiC PVD coating. The machinability of CGI and wear mechanisms were analyzed using pre-cutting characterization, in-process optical microscopy, and post-test SEM analysis. The results revealed that CGI microstructural variations only affected tool life for Tool A, with a 110% increase in tool life between machining CGI Grade B and Grade A, but that the effects were negligible for all other tools. Tool C had a 250% and 70% longer tool life compared to the next best performance (Tool A) for CGI Grade A and CGI Grade B, respectively. With its thick CVD-coating, Tool C consistently outperformed the others due to its superior protection of the flank face and cutting edge under high-stress conditions. The cutting-induced stresses played a more significant role in the tool wear process than minor differences in workpiece microstructure or tool properties, and a thick CVD coating was most effective in addressing the tool wear effects for the extreme roughing conditions. However, differences in tool life for Tool A showed that tool behavior cannot be predicted based on a single system parameter, even for extreme conditions. Instead, tool properties, workpiece properties, cutting conditions, and their interactions should be considered collectively to evaluate the extent that an individual parameter impacts machinability. This research demonstrates that a comprehensive approach such as this can allow for more effective tool selection and thus lead to significant cost savings and more efficient manufacturing operations.

Toward Surface Passivation of Black Phosphorus via a Self-Assembled Ferrocene Molecular Layer.

Black phosphorus (BP), a promising two-dimensional material, faces significant challenges for its applications due to its instability in air and water. Herein, molecular dynamics simulations reveal that a self-assembled ferrocene (FeCp2) molecular layer can form on BP surfaces and remain stable in aqueous environments, predicting its effectiveness for passivation. This theoretical finding is corroborated by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and optical microscopy observations. In addition, atomic force microscopy analysis confirms that ferrocene-passivated BP flakes with thicknesses of <10 nm exhibit minimal degradation over 25 days. Density functional theory calculations further show that ferrocene stabilizes BP and modulates its band gap, improving its electronic applicability. Notably, we find that the passivation of BP by metallocenes is universal because other metallocenes (VCp2, MnCp2, and NiCp2) exhibit similar adsorption behaviors. These findings underscore the potential of metallocenes as versatile protective layers for BP and other materials that are not stable in air.

Optimizing process parameters for enhanced formability and fracture behavior in single point incremental forming of SS310 sheets

This research investigates the forming and fracture behavior of stainless steel 310 Grade sheets using the single point incremental forming (SPIF) process under various parameters: ball diameter, spindle speed, feed rate, and vertical step down. Employing an L9 orthogonal array suggested by Taguchi, the study evaluates formability through stress and strain-based forming limit diagrams (FLD). Structural changes were analyzed using scanning electron microscopy fractography and optical microscopy. The highest level of formability was identified at the spindle speed of 100 rpm, feed rate of 600 mm/min, ball diameter of 12 mm, and a vertical step-down of 0.3 mm. Formability analysis is given variations with a maximum of 0.931 at a wall angle of 72.71°, and minimum and medium values of 0.423 and 0.63 at all angles of 60° and 66.24°, respectively. The least and most moderate formability levels showed an 11% variation, and the least and highest formability limits had a 21% higher formability limit. The stress-based limits also increased by 10% for moderate to better formability. The findings indicate that formability increases with lower vertical step down and feed rate, as well as higher spindle speed and ball diameter. This study provides valuable insights into optimizing SPIF process parameters to enhance the quality and structural integrity of formed SS310 components.

Towards the Sustainable Removal of Heavy Metals from Wastewater Using Arthrospira platensis: A Laboratory-Scale Approach in the Context of a Green Circular Economy

The use of living Arthrospira platensis (A. platensis) cultures emerges as a promising green solution for the bioremediation of water contaminated by toxic metal waste. The scope of the present study is to evaluate the microalga’s potential in heavy metal remediation, in the case of multi-metal-treated (multi-MT) systems. For this reason, A. platensis cultures were exposed to mono- and multi-metal solutions of Cu, Cd, Ni, Pb, and Zn, and their metal adsorption ability was investigated. The heavy metal removal efficiency of A. platensis cultures was evaluated using atomic absorption spectroscopy (AAS). Additionally, the cultures were examined using Fourier transform infrared (FTIR) spectroscopy, Near-Infrared (NIR) Spectroscopy, UV-Vis spectrophotometry, and optical microscopy, together with pH and electrical conductivity (EC) measurements to evaluate the quality of the cultures and the changes induced by heavy metal stress. The results showed that metal removal is still efficient in multi-MT cultures. In particular, Cu, Cd, Pb, and Zn removal of multi-MT cultures is elevated or relative to the respective removal of the mono-metal-treated (mono-MT) cultures, showing a synergistic or cooperative interaction between the metals, while the removal of Ni of multi-MT cultures decreased compared to Ni of mono-MT cultures, showing an antagonistic interaction to the other metals. The study shows that A. platensis is considered an effective microalga toward the bioremediation of multi-metal polluted cultures.

APPLICATION OF IONIZING RADIATION IN THE PRESERVATION AND CONSERVATION OF TAXIDERMIED ANIMAL SKINS IN NATURAL HISTORY MUSEUMS&lt;i&gt;&lt;/i&gt;

The great interest in the development of research involving ionizing radiation aims to significantly increase the conservation of the skins of taxidermized animals, both for scientific collections and on display, causing their infection and disinfestation, without altering their originality, reducing the use of chemical products, presenting a safe and efficient technology. The preservation of taxidermied mammals has been widely used for educational, scientific and Museum display purposes. However, prolonged exposure to environmental factors or the excessive use of chemicals to store these materials in the collection can affect the integrity of the skin of these animals. In this study, we investigated the effects of gamma radiation on the structure and composition of the skin of taxidermied mammals, with the aim of contributing to a better understanding of conservation processes and the potential risks they may entail. Taxidermy is an animal preservation technique that has been used for centuries, allowing specimens to be arranged in their natural form and/or preserved for scientific studies. Samples of skin from animals from the Brazilian flora were selected, deer, coati, prawn and bison, and these samples were irradiated at doses of 1, 3, 5, 10 and 15 kGy. After gamma irradiation, they were characterized by colorimetry, scanning electron microscopy (SEM), optical microscopy (OM), infrared microscopy (FTIR) and mechanical analysis. The results show that the doses of gamma irradiation that the samples were subjected to did not compromise their physical and chemical integrity. This indicates the possibility of using gamma radiation for disinfestation and disinfection.

Morphological variation in the postabdomen of Camptocercus dadayi Stingelin, 1913 (Cladocera: Anomopoda: Chydoridae)

We investigated the morphological variations of Camptocercus dadayi Stingelin, 1913 in different populations across South America (Argentina, Brazil, Chile, and Colombia) under optical microscope. Significant variations were observed in the morphology of the postabdomen, especially in the patterns of the marginal denticles, lateral fascicles and terminal claw. The variations follow a geographic pattern throughout South America. These variations suggest morphologic diversity in the species, highlighting the importance of variation studies for the accurate identification and delimitation of species within Camptocercus.

Panchromatic Absorption of Unsymmetrical Donor-Acceptor Dyes Based on a Meta-Conjugated 1,3,5-Heteroaryltriazine Core.

Attachment of three different heterocycles with electron donor or acceptor character to a central 1,3,5-triazine core generates readily soluble side-chain free dyes with two displaying soft crystalline mesomorphism and one displaying a nematic liquid crystal phase as confirmed by polarized optical microscopy, calorimetry, gravimetric analysis, and powder X-ray diffraction. Equally intriguing is the dyes' relatively strong electronic communication between donor and acceptor subchromophores that are meta-conjugated to one another, which is experimentally observed as a broad intramolecular charge-transfer absorption that can extend over 100 nm past the most intense absorption event and is computationally confirmed through density functional theory (DFT) evaluations of the molecular ground- and excited-state properties. This molecular design permits the preparation of dyes with panchromatic absorption not just based on the additive absorption of individual subchromophores.

Identification of the Morphology of Tamarix spp in the Mexicali Valley, Baja California, Mexico

Objective: The predominant species of Tamarix spp in the Mexicali Valley is unknown, and due to the scarce information available, this study aims to expand the knowledge of the morphology of Tamarix spp in the Mexicali Valley, Baja California, Mexico. Design/methodology/approach: For this research, five branches with inflorescences and roots of Tamarix spp trees were collected from four selected locations in the Mexicali Valley. The collection was carried out during the flowering season from March to August, considering branches between 2.50 and 3.50 cm in height. The morphological descriptions were based on fresh plants using an Olympia optical microscope. Results: After the morphological analysis was carried out at the different sampling sites, the predominant salt cedar genotype found in the Mexicali Valley corresponded to Tamarix chinensis. In addition, it was found high electrical conductivity measured in the upper soil layer (20 cm depth) was found to be caused by the excretion of salts through the glands of the leaves of this species. Consequently, salt cedar species can inhibit other vegetation types, although it can benefit honey bee production. Findings/conclusions: Tamarix chinensis was the predominant salt cedar species throughout the sampling sites under the conditions of this study.The high electrical conductivity measured in the upper soil layer (20 cm depth) shows that salt cedar species can inhibit the growth of other vegetation types, although it can be beneficial for honey bee production.

Colloidal Nanoparticles Hold Elementary Charge in Nonpolar Solvent.

The net charge of individual nanoparticles in nonpolar solvents plays a critical role in their intrinsic properties like charge carrier lifetime, electron transport, and interparticle interactions. However, there is a long-standing belief that the oil-dispersed nanoparticles inherently possess no net charge. This work presents an approach for directly quantifying the net charge of individual nanoparticles. We employ an alternating electric field coupled with in situ observation under an optical microscope to analyze the force and motion of sub-50 nm silver nanoparticles. This technique directly reveals that around 1-10% of these colloidal nanoparticles carry a single elementary charge in nonpolar solvents, while the majority remain essentially neutral. This represents the first quantitative measurement of a single nanoparticle's charge in a nonpolar solvent.

Observation and characterization of grain boundaries in monolayer MoSe2

Abstract Grain boundaries of MoSe2 impact their electrical, optoelectronic, and mechanical properties. The simple, efficient and rapid method to visualize the large-area grains and grain boundaries in MoSe2 is highly demanded but still lacking. Here, we show a simple, efficient, and rapid method for visualization of large-area grain boundaries in continuous CVD monolayer MoSe2 films that were transferred on a SiO2 substrate. As the monolayer MoSe2 was exposed to vapor hydrofluoric acid (VHF), the VHF diffused through grain boundary-based defects in the MoSe2 films and resulted in differential etching of the SiO2 at the MoSe2 grain boundaries and the SiO2 underneath the MoSe2 grains. The positions of the grain boundaries were prominent owing to the height difference of SiO2 and can be observed using optical microscopy, scanning electron microscopy, or Raman spectroscopy. This method would contribute to optimizing the growth process of MoSe2 and its device application.

Tribological performance of modified graphene as an additive in copper wire drawing lubricant

PurposeThis study aims to explore the use of modified graphene (MG) in copper wire drawing lubricants to enhance their friction-reducing and anti-wear capabilities.Design/methodology/approachGraphene was modified using oleic and stearic acids to improve its dispersibility in lubricants. Various concentrations of MG were then introduced into a copper wire drawing lubricant to investigate their tribological performance. Wear mechanisms were evaluated with scanning electron microscopy, optical microscopy, Raman spectroscopy and energy dispersive spectroscopy (EDS).FindingsThe best concentration of MG is 1.5 Wt.%, at which the copper wire drawing oil exhibits a friction coefficient and wear rate of 0.085 and 2.11 × 10−6 mm3/Nm, respectively, representing decreases of 22.7% and 47.6% compared to the base oil. It was further found that the addition of 1.5 Wt.% MG to a copper wire drawing fluid with a water content of 70% resulted in a 30.3% reduction in friction coefficient compared to the base oil. Raman spectroscopy and EDS analysis confirmed that the MG tribo-film formed on the worn copper disc effectively minimized friction and wear.Originality/valueThis study analyzes the tribological performance of different concentrations of MG in copper wire drawing oils, establishing a basis for the application of MG in copper wire drawing fluids.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2024-0399/

Effect of Pre-Emulsified Flaxseed Oil Containing Rutin on the Quality of Nemipterus virgatus Surimi Gel: Gelatinization Properties, Storage Stability, and Protein Digestibility.

Rinsing during surimi protein processing can result in the loss of essential nutrients, such as fats and minerals. Therefore, supplementing functional fats in a stable form can make up for the fat loss of surimi during the rinsing process. This research aimed to investigate the effects of incorporating pre-emulsified flaxseed oil with different concentrations of rutin (0, 0.5, 1.5, 2.5, and 3.5%, dissolved in flaxseed oil, w/v) to Nemipterus virgatus surimi on the gelatinization properties, lipid oxidation, and in vitro static simulated digestion characteristics of surimi gels. The results indicated that the addition of 1.5% rutin significantly improved the water-holding capacity and decreased the cooking loss rate of surimi gel (p < 0.05). The results of optical microscopy and scanning electron microscopy showed that the addition of 1.5% rutin promoted a denser network structure of surimi gel. Furthermore, the incorporation of rutin effectively slowed lipid oxidation in pre-emulsified flaxseed oil surimi gel. Compared with the gel group containing only pre-emulsified flaxseed oil, the addition of rutin significantly reduced the levels of volatile base nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARSs) in the gel and also mitigated the decline in acidity (p < 0.05). Moreover, the addition of rutin significantly inhibited the decrease in pH of surimi gel during storage (p < 0.05). In vitro static simulated digestion demonstrated that the addition of 1.5% rutin enhanced the protein digestibility from 71.2% to 77.2% of the surimi gel. Therefore, adding pre-emulsified oil containing an appropriate amount of rutin to surimi can not only compensate for the fat loss during the surimi rinsing process but also effectively improve the quality characteristics of surimi gels. This research will provide a theoretical basis for the effective addition of functional lipids in surimi products and the development of nutritious and healthy surimi products.

The Investigation of Stefan Luchian Heritage Paintings—A Multi-Analytical Approach

Based on a multi-analytical approach involving mobile techniques and lab-based devices (XPS, portable and micro-Raman spectroscopies, and ATR-FTIR spectroscopy, combined with SEM/EDS and optical microscopy), this study presents the first in-depth investigation of two cultural heritage artworks painted by the famous Romanian artist Ștefan Luchian. The research highlights the artist’s use of a wide range of colors, with his palette including classic pigments such as ochers, lead white, barium white, zinc white, and viridian, as well as contemporary colors such as cobalt purple, alizarin crimson, and the little-known indium yellow. Additionally, attempts are made to characterize the binders used in the paintings, which include linseed oil and animal glue. Beyond identifying the types of pigments and materials used by the artist and assessing the degradation stage of the paintings, this study is the first to provide information regarding the use of In2O3 as a yellow pigment in artwork.