Topographic Images Research Articles

Machine learning for multi-dimensional performance optimization and predictive modelling of nanopowder-mixed electric discharge machining (EDM)

AbstractAluminium 6061 (Al6061) is a widely used material for various industrial applications due to low density and high strength. Nevertheless, the conventional machining operations are not the best choice for the machining purposes. Therefore, amongst all the non-conventional machining operations, electric discharge machining (EDM) is opted to carry out the research due to its wide ability to cut the materials. But the high electrode wear rate (EWR) and high dimensional inaccuracy or overcut (OC) of EDM limit its usage. Consequently, nanopowder is added to the dielectric medium to address the abovementioned issues. Nanopowder mixed EDM (NPMEDM) process is a complex process in terms of performance predictability for different materials. Similarly, the interactions between the process parameters such as peak current (Ip), spark voltage (Sv), pulse on time (Pon) and powder concentration (Cp) in dielectric enhance the parametric sensitivity. In addition, the cryogenic treatment (CT) of electrodes makes the process complex limiting conventional simulation approaches for modelling inter-relationships. An alternative approach requires experimental exploration and systematic investigation to model EWR and overcutting problems of EDM. Thus, artificial neural networks (ANNs) are used for predictive modelling of the process which are integrated with multi-objective genetic algorithm (MOGA) for parametric optimization. The approach uses experimental data based on response surface methodology (RSM) design of experiments. Moreover, the process physics is thoroughly discussed with parametric effect analysis supported with evidence of microscopic images, scanning electron microscopy (SEM) and 3D surface topographic images. Based on multi-dimensional optimization results, the NT brass electrode showed an improvement of 65.02% in EWR and 59.73% in OC using deionized water. However, CT brass electrode showed 78.41% reduction in EWR and 67.79% improved dimensional accuracy in deionized water. In addition to that, CT brass electrode gave 27.69% less EWR and 81.40% improved OC in deionized water compared to kerosene oil.

Scanning tunneling microscopy study of epitaxial Fe3GeTe2 monolayers on Bi2Te3

Introducing magnetism to the surface state of topological insulators, such as Bi2Te3, can lead to a variety of interesting phenomena. We use scanning tunneling microscopy (STM) to study a single quintuple layer (QL) of the van der Waals magnet Fe3GeTe2 (FGT) that is grown on Bi2Te3 via molecular beam epitaxy. STM topographic images show that the FGT grows as free-standing islands on Bi2Te3 and outwards from Bi2Te3 steps. Atomic resolution imaging shows triangular lattices of 390 ± 10 pm for FGT and 430 ± 10 pm for Bi2Te3, consistent with the respective bulk crystals. A moiré pattern is observed on FGT regions with a periodicity of 4.3 ± 0.4 nm that can be attributed solely to this lattice mismatch and thus indicates zero rotational misalignment. While most of the surface is covered by a single QL of the FGT, there are small double QL regions, as well as regions with distinct chemical terminations due to an incomplete QL. The most common partial QL surface termination is the FeGe layer, in which the top two atomic layers are missing. This termination has a distinctive electronic structure and a 3 x 3R30∘ reconstruction overlaid on the moiré pattern in STM images. Magnetic circular dichroism measurements confirm these thin FGT films are ferromagnetic with T C ∼190 K.

Experimental study of the effect of target composition and heat treatment on the Ag deposit on the adhesion of the surfaces used in microelectromechanical systems (MEMS)

Adhesion force is one of the major factors in MEMS technology specifically during micro assembling via micro grippers. Regarding the light weight of MEMS devices, the contact force between MEMS devices and the microgripper surface causes distinct problems such as sticking the MEMS surface to the microgripper, so the assemble procedure can be affected and microparts not be placed in the right position. so decreasing adhesion force has a significant role in improving micron assembly. Accordingly, in the current research work, the effects of various coating materials, deposition, and annealing temperatures on the surface roughness of microgripper substrate and its morphology are experimentally investigated considering the DC sputtering magnetron method to decrease adhesion force between microgripper substrate and MEMS device. For this purpose, seventeen silicon surfaces were used of which sixteen of them coated and one is non-coated. Deposited substrates can be classified into four groups four of them are deposited with double layers using two kinds of coating materials including Ti/Ag, SiO2/Ag, Ti/Ag-Pd-Cu, and SiO2/Ag-Pd-Cu respectively. After sample deposition, the AFM method was used to measure, the topographic images, the surface roughness, and the adhesion force. Regarding the differences in layers and distinct temperatures, the height and shape of hillocks directly depend on deposition and preheating temperature ranges. So as the deposition and preheating temperature increase, more hillocks grow and the adhesion force is more consequently. to 373 K and 573 K. Additionally, these changes result in changes in adhesion force.

Precise Surface Profiling at the Nanoscale Enabled by Deep Learning.

Surface topography, or height profile, is a critical property for various micro- and nanostructured materials and devices, as well as biological systems. At the nanoscale, atomic force microscopy (AFM) is the tool of choice for surface profiling due to its capability to noninvasively map the topography of almost all types of samples. However, this method suffers from one drawback: the convolution of the nanoprobe's shape in the height profile of the samples, which is especially severe for sharp protrusion features. Here, we report a deep learning (DL) approach to overcome this limit. Adopting an image-to-image translation methodology, we use data sets of tip-convoluted and deconvoluted image pairs to train an encoder-decoder based deep convolutional neural network. The trained network successfully removes the tip convolution from AFM topographic images of various nanocorrugated surfaces and recovers the true, precise 3D height profiles of these samples.

Fibroblasts and osteoblasts behavior after contact with different titanium surfaces used as implant abutment: An in vitro experimental study

BackgroundThe goal of this in vitro study was to compare three different surfaces: two types of implant surfaces commercially available ([a] smooth/machined and [b] acid-treated surface) versus (c) anodized surface. Discs were manufactured with commercially pure titanium (CP) grade IV, which were subsequently analyzed by scanning microscopy and fibroblastic and osteoblastic cell cultures. MethodsNinety-nine discs (5 × 2 mm) were manufactured in titanium grade IV and received different surface treatments: (i) Mach group: machined; (ii) AA group: double acid etch; and (iii) AN group: anodizing treatment. Three discs from each group were analyzed by Scanning Electron Microscopy (SEM) to obtain surface topography images and qualitatively analyzed by EDS. Balb/c 3T3 fibroblasts and pre-osteoblastic cells (MC3T3-E1 lineage) were used to investigate each group's biological response (n = 10/cellular type). The data were compared statistically using the ANOVA one-way test, considered as a statistically significant difference p < 0.05. ResultsThe AA group had numerous micropores with diameters between 5 and 10 μm, while nanopores between 1 and 5 nm were measured in the AN group. The EDX spectrum showed a high titanium concentration in all the analyzed samples. The contact angle and wetting tension were higher in the AA, whereas similar results were observed for the other groups. A lower result was observed for base width in the AA, which was higher in the other two groups. The AN showed the best values in the fibroblast cells, followed by Mach and AA; whereas, in the culture of the MC3T3 cells, the result was precisely the opposite (AA > Mach > AN). There was similar behavior for cell adhesion for the test groups (Mach and AN), with greater adhesion of Balb/c 3T3 fibroblasts compared to MC3T3 cells; in the AA group, there was greater adherence for MC3T3 cells compared to Balb/c 3T3 fibroblasts. ConclusionsThe findings suggest that different surface characteristics can produce different biological responses, possibly cell-line dependent. These findings have important implications for the design of implantable medical devices, where the surface characteristics can significantly impact its biocompatibility.

Atom Filtering Algorithm and GPU-Accelerated Calculation of Simulation Atomic Force Microscopy Images

Simulation of atomic force microscopy (AFM) computationally emulates experimental scanning of a biomolecular structure to produce topographic images that can be correlated with measured images. Its application to the enormous amount of available high-resolution structures, as well as to molecular dynamics modelling data, facilitates the quantitative interpretation of experimental observations by inferring atomistic information from resolution-limited measured topographies. The computation required to generate a simulated AFM image generally includes the calculation of contacts between the scanning tip and all atoms from the biomolecular structure. However, since only contacts with surface atoms are relevant, a filtering method shall highly improve the efficiency of simulated AFM computations. In this report, we address this issue and present an elegant solution based on graphics processing unit (GPU) computations that significantly accelerates the computation of simulated AFM images. This method not only allows for the visualization of biomolecular structures combined with ultra-fast synchronized calculation and graphical representation of corresponding simulated AFM images (live simulation AFM), but, as we demonstrate, it can also reduce the computational effort during the automatized fitting of atomistic structures into measured AFM topographies by orders of magnitude. Hence, the developed method will play an important role in post-experimental computational analysis involving simulated AFM, including expected applications in machine learning approaches. The implementation is realized in our BioAFMviewer software (ver. 3) package for simulated AFM of biomolecular structures and dynamics.

Automated Scanning Probe Tip State Classification without Machine Learning.

The manual identification and in situ correction of the state of the scanning probe tip is one of the most time-consuming and tedious processes in atomic-resolution scanning probe microscopy. This is due to the random nature of the probe tip on the atomic level, and the requirement for a human operator to compare the probe quality via manual inspection of the topographical images after any change in the probe. Previous attempts to automate the classification of the scanning probe state have focused on the use of machine learning techniques, but the training of these models relies on large, labeled data sets for each surface being studied. These data sets are extremely time-consuming to create and are not always available, especially when considering a new substrate or adsorbate system. In this paper, we show that the problem of tip classification from a topographical image can be solved by using only a single image of the surface along with a small amount of prior knowledge of the appearance of the system in question with a method utilizing template matching (TM). We find that by using these TM methods, comparable accuracy and precision can be achieved to values obtained with the use of machine learning. We demonstrate the efficacy of this technique by training a machine learning-based classifier and comparing the classifications with the TM classifier for two prototypical silicon-based surfaces. We also apply the TM classifier to a number of other systems where supervised machine learning-based training was not possible due to the nature of the training data sets. Finally, the applicability of the TM method to surfaces used in the literature, which have been classified using machine learning-based methods, is considered.

Novel preparation of Sb2O3:Ag/Si solar cell fabricated utilising thermal evaporation method: studies on structural, morphology microstructural, topographic imaging, optical, and electrical properties for photovoltaic cell based electronic device applications

Novel preparation of Sb2O3:Ag/Si solar cell fabricated utilising thermal evaporation method: studies on structural, morphology microstructural, topographic imaging, optical, and electrical properties for photovoltaic cell based electronic device applications

Evaluation of intelligent packaging functions of black carrot extract-infused polyvinyl alcohol nanofibers

In this study, we aimed to evaluate the characteristic changes in polyvinyl alcohol-based nanofibers after being stored with black sea salmon fillets. For this purpose, electrospun nanofibers were produced as control (PVA), black carrot extract-incorporated (PVAB), and extract+SnO2 incorporated (PVASN), and their properties were compared. Morphological results showed the formation of regular ultrafine nanostructures, and differences between nanofiber samples were evaluated by measuring fiber diameters. Nanofiber sizes increased with the addition of black carrot and SnO2. Elemental analysis was performed to obtain information about the concentration in the nanofibers. Different O and Sn concentrations indicated that important constituents of anthocyanins and SnO2 were attached to the samples. The location of C, O, Sn atoms was determined by Energy Spectrum Analysis (EDS) color mapping, which confirmed the attachment of Sn in the PVASN sample. To elucidate the relationship between spoilage and the absorption of volatiles from smoked salmon fillets, nanofibers and fillets were kept together in a petri dish at room temperature. After being stored with salmon meat, the PVASN sample showed fewer entanglements without any defects. Upon exposure to volatiles, molecular structures changed, and water contact angle values decreased. X-Ray Diffraction (XRD) results indicated the state of the polymer matrix and SnO2. Chemical bond interactions with released volatiles effected the peak parameters of nanofibers. 3D and 2D surface topographical images of PVASN were also compared before and after storage using a profilometer. This study's results showed that functionalized nanofibers with extract-SnO2 could be applied as an intelligent food packaging layer, providing valuable data about the potential usage of electrohydrodynamic processing.

How Topographic Diffusion-Weighted Imaging Patterns can Predict thePotential Embolic Source.

To develop an imaging prediction model for patients with embolic stroke of undetermined source (ESUS), we investigated the association of topographic diffusion-weighted imaging (DWI) patterns with potential embolic sources (PES) identified by transesophageal echocardiography. From atotal of 992 consecutive patients with embolic stroke, 366 patients with the ESUS group were selected. ESUS was defined as no atrial fibrillation (Af) within 24h from admission and no PES after general examination. Clinical variables include age (> 80years, 70-80 years), sex, vascular risk factors and left atrial diameter > 4 cm. Age, sex and vascular risk factors adjusted odds ratio of each DWI for the different PESs were calculated. DWI was determined based on the arterial territories. Middle cerebral arteries were divided into 4segments, i.e., M1-M4. Moreover, M2segments were subdivided into superior and inferior branches. The 366 patients consisted of 168 with paroxysmal Af (pAf), 77with paradoxical embolism, 71with aortic embolism and 50with undetermined embolism after transesophageal echocardiography. The variables adjusted odds ratio (OR) of internal carotid artery (OR: 12.1, p = 0.037), M1(4.2, p = 0.001), inferior M2(7.5, p = 0.0041) and multiple cortical branches (12.6, p < 0.0001) were significantly higher in patients with pAf. Striatocapsular infarction (12.5, p < 0.0001) and posterior inferior cerebellar artery infarcts (3.6, p = 0.018) were significantly associated with paradoxical embolism. Clinical variables adjusted OR of multiple small scattered infarcts (8.3, p < 0.0001) were significantly higher in patients with aortic embolism. The associations of DWI with different PES have their distinctive characteristics and DWI along with clinical variables may help predict PES in patients with ESUS.

Study of Phase Imaging Contrast Optimization in Tapping Mode Atomic Force Microscopy

In tapping mode atomic force microscopy (TM‐AFM), the phase image can reveal more about the physicochemical properties of the sample surface than the topography image, making it widely utilized in fields such as materials science and life sciences. However, obtaining high phase contrast in phase images during experiments is challenging, thus studying the phase imaging theory of TM‐AFM and optimizing phase contrast methods hold significant importance. This paper derives a theoretical expression for phase contrast based on phase theory, discovering that phase contrast is directly related to the frequency ratio and background dissipation quality factor. Through theoretical, experimental, and simulation approaches, optimization methods for phase contrast were proposed from the perspectives of frequency ratio and background dissipation quality factor as follows: (1) By fitting experimental results with the theoretical expression for phase contrast, the optimal frequency ratio for scanning can be determined, and imaging with this optimal ratio can enhance phase contrast and (2) reducing the width ratio between the free and fixed ends of the probe can decrease background dissipation, increase the proportion of core dissipation in the total energy dissipation of the probe, and thereby improve phase imaging contrast. These findings are significant in guiding TM‐AFM phase scanning experiments and optimizing phase imaging contrast.

Calcium accumulation or iron deposition: Delving into the temporal sequence of amyotrophic lateral sclerosis pathophysiology in the primary motor cortex.

Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, but an in vivo understanding of its early pathology remains limited. A recent study used topographic layer imaging to investigate iron and calcium accumulation in the primary motor cortex (M1) of patients with ALS compared with controls. Despite the preserved cortical thickness, ALS patients showed increased iron in layer 6 and calcium accumulation in layer 5a and the superficial layer. Calcium accumulation was particularly prominent in the low-myelin borders, potentially preceding the demyelination. This study reveals a novel in vivo pathology in ALS, suggesting that calcium dysregulation may precede iron accumulation and contribute to early M1 cell degeneration. Further investigation using quantitative susceptibility mapping and complementary techniques, such as diffusion kurtosis imaging, along with ultrahigh-field magnetic resonance imaging, into the role of calcium and early intervention strategies is warranted.

Metrology of Silicon Wafers through Synchrotron Section Topography and X-ray Diffraction Imaging

Metrology of Silicon Wafers through Synchrotron Section Topography and X-ray Diffraction Imaging

Atomic force microscopy observation of surface morphologies and measurements of local contact potential differences of amorphous solid water samples deposited at 15 and 100 K.

We use an ultra-high vacuum cryogenic atomic force microscope to investigate the surface morphology of amorphous solid water (ASW) prepared by oblique deposition of water vapor onto Si(111)7 × 7 substrates at temperatures of 15 and 100 K. Height-height correlation function analysis of topographic images suggests that ASW at 15 K has a columnar structure and that the typical diameter of the column is 5-10 nm. At 100 K, the typical diameter is 10-30 nm, although columnar features are less prominent. The surface roughness (i.e., deviation of the height) is greater at 15 K than at 100 K, indicating that the surface at 100 K exhibits a relatively flat morphology. This result implies that transient diffusion of deposited water molecules affects the surface morphology at 100 K. In addition, measurements of the local contact potential difference between the tip and the ASW surface suggest that the magnitude of the negative surface potential at the microscopic scale, which is attributed to spontaneous polarisation, cannot simply be scaled by the thickness of ASW as predicted in previous experiments with Kelvin probes.

An Improved Imaging Method Based on Optimal Topographic Imaging Plane Reconstruction for Nonlinear Trajectory SAR

An Improved Imaging Method Based on Optimal Topographic Imaging Plane Reconstruction for Nonlinear Trajectory SAR

Characterizing morphological alterations in blood related disorders through Atomic Force Microscopy.

Atomic Force Microscopy (AFM) is a very flexible method that can create topographical images from a range of materials and image surfaces. Significantly, AFM has emerged as an invaluable tool for dissecting the morphology and biochemical aspects of body cells and tissues. The high-resolution imaging capabilities of AFM enable researchers to discern alterations in cell morphology and understand the underlying mechanisms of diseases. It contributes to understanding disease etiology and progression. In the context of this review, our focus will be directed towards elucidating the pivotal role of AFM in analysis of blood related disorders. Through detailed comparisons with normal cells, we delve into the alterations in size, shape, and surface characteristics induced by conditions such as cancer, diabetes, anaemia, and infections caused by pathogens. In essence, various work described in this article highlights to bridge the gap between traditional microscopy and in-depth analysis of blood-related pathologies, which in turn offers valuable perspectives for both research and clinical applications in the field.

Nanoscale visualization of the anti-tumor effect of a plasma-activated Ringer's lactate solution.

Plasma-activated Ringer's lactate solutions (PALs), which are Ringer's lactate solutions treated with non-thermal atmospheric-pressure plasma, have an anti-tumor effect and can be used for chemotherapy. As the anti-tumor effect of the PAL is influenced by the cell-treatment time, it is necessary to monitor the structural changes of the cell surface with non-invasive, nanoscale, and time-lapse imaging to understand the anti-tumor effect. In this study, to characterize the anti-tumor effect of the PAL, we used scanning ion conductance microscopy (SICM), using glass nanopipettes as probes, to visualize the structural changes of the cell surface. SICM time-lapse topographic imaging visualized a decrease in the movement of lamellipodia in normal cells and cancer cells after the PAL treatment. Furthermore, in normal cells, protrusive structures were observed on the cell surface. Time-lapse imaging using SICM allowed us to characterize the differences in the morphological changes between the normal and cancer cells upon exposure to the PAL.

Effect of Silver Nanoparticles Synthesized by Pulsed Laser Ablation in Liquid on the Hematological, Hepatic, and Renal Functions of Albino Rats

Silver nanoparticles (Ag-NPs) have unique properties as antibacterial effects against locally isolated clinical Escherichia coli. In this study, the evaluated the antibacterial activity of AgNPs, which were synthesized by laser ablation, against locally isolated clinical Escherichia coli on nutrient agar media in vitro. Then assessed the toxicity of the bactericidal dose in albino rats in vivo with hematological, liver, and kidney functions as vital parameters. AgNPs were synthesized by pulsed laser ablation in liquid (PLAL). AgNPs’ shape and nano size were characterized by atomic force microscopy (AFM), UV-vis spectroscopy, and scanning electron microscopy (SEM). UV peak absorption was observed at 434 nm, which produced an average particle diameter of 28.09 nm. The SEM and AFM topography images of the synthesized nanoparticles showed that they had a spherical shape. Also studied was the toxicity of the synthesized AgNPs in vivo. Four groups of albino rats were used. The liver and kidneys were found to be the main organs that accumulate AgNP. In this study, we examined the influence of intraperitoneally injected AgNPs on blood parameters (complete blood picture) and liver and kidney functions of albino rats. Blood ALP and serum test (GOT and GPT), serum urea and serum creatinine were analyzed at 15, 30, and 60 days after injection of 200 mg/kg of PLAL-synthesized AgNP. The results did not indicate statistically significant differences between the control and treatment groups in blood picture and enzyme levels tested that indicate proper liver function. Additionally, no differences in kidney functions were found during varying time intervals in the blood of rats. Thus, PLAL-synthesized AgNPs could inhibit Escherichia coli bacterial growth.

(Invited) Transparent Conductive Films of PEDOT:PSS-Amino Acid Composite

Transparent conductive electrode is an important component of optoelectronic devices such as light emitting diodes, photodiodes, and photovoltaic cells as well touchscreen technology. Growing demand for these technologies, as well as need for functionalities such as cost-effectiveness and flexibility, has resulted in various research on developing organic polymer-based transparent electrodes as an alternative to indium tin oxide (ITO) which is the current industry standard. One of the organic conducting polymers most commonly studied for their potential to be used as ITO-free transparent electrodes is PEDOT:PSS due to its high transmittance as a thin film, solution processability, flexibility, environmental stability, and commercial availability. There have been various works carried out to improve the conductivity of the PEDOT:PSS-based thin films by introducing dopants to improve the charge transport. We present our results demonstrating that not only the conductivity but also the transmittance of PEDOT-PSS-based films can be significantly improved by the introduction of amino acids such as phenylalanine in the film. We have observed that this enhancement in conductivity and optical transmittance of PEDOT:PSS-phenylalanine composite film is retained even when the amount of amino acid in the composite films is larger than the amount of PEDOT:PSS. We will present our study on the charge transport mechanism on these films based on electrochemical impedance spectroscopy (EIS) measurements. We will also further present our studies based on Scanning Electron Microscopy (SEM) as well as Scanning Probe Microscopy techniques such as topography imaging and conducting probe atomic force microscopy (CP-AFM) to elucidate the relationship between film morphology and charge transport in these composite films. The use of bioderived materials such as amino acids to create transparent composite films could open up avenues for developing and integrating bio-based materials in future electronics, help improve the environmental footprint of the electronics, and potentially also allow for the development of materials with a higher degree of biocompatibility for their application in bioelectronics.

Structure-preserving fixation allows scanning electron microscopy to reveal biofilm microstructure and interactions with immune cells.

Pseudomonas aeruginosa is a pathogen that forms robust biofilms which are commonly associated with chronic infections and cannot be successfully cleared by the immune system. Neutrophils, the most common white blood cells, target infections with pathogen-killing mechanisms that are rendered largely ineffective by the protective physicochemical structure of a biofilm. Visualisation of the complex interactions between immune cells and biofilms will advance understanding of how biofilms evade the immune system and could aid in developing treatment methods that promote immune clearance with minimal harm to the host. Scanning electron microscopy (SEM) distinguishes itself as a powerful, high-resolution tool for obtaining strikingly clear and detailed topographical images. However, taking full advantage of SEM's potential for high-resolution imaging requires that the fixation process simultaneously preserve both intricate biofilm architecture and the morphologies and structural signatures characterising neutrophils responses at an infection site. Standard aldehyde-based fixation techniques result in significant loss of biofilm matrix material and morphologies of responding immune cells, thereby obscuring the details of immune interactions with the biofilm matrix. Here we show an improved fixation technique using the cationic dye alcian blue to preserve and visualise neutrophil interactions with the three-dimensional architecture of P. aeruginosa biofilms. We also demonstrate that this technique better preserves structures of biofilms grown from two other bacterial species, Klebsiella pneumoniae and Burkholderia thailandensis.