Fine Protrusions Research Articles

FIB fabrication and electron emission characteristics of overhanging tungsten and platinum nanostructures

The recent advancement in nanofabrication technology has enabled realization of vacuum electron devices with nanogap spacing. These devices have advantages over semiconductor counterparts due to possible operation under hard conditions and some unique functionalities. The challenging task, however, lies with the full understanding of their current–voltage (I–V) characteristics, resulting from various electron emission mechanisms. The reliable extraction of device parameters is, therefore, vital for its potential applications. An attempt has, therefore, been made here to fabricate two three-dimensional overhanging electrodes of tungsten and platinum with a nanoscale gap of 70–100 nm on glass substrates using chemical vapor deposition and focused ion beam milling. Their (I–V) characteristics measured in situ at ∼10−6 mbar are shown to follow the Child–Langmuir law and Fowler–Nordheim field emission at low and high-bias conditions, respectively. The extraction of parameters with a simple procedure suggested earlier yields an effective emission area of ∼3510 Å2, work function of ∼2.5 eV, and field enhancement factor (β) of ∼ 1.8 for tungsten; the values for platinum are 12.5 Å2, 3.0 eV, and 5.0, respectively. The higher β in the case of platinum can be attributed to the formation of a comparatively rough emitter surface with some fine protrusions. The nanostructure gives a current spike at high voltages, which marks its transition to an explosive emission state, breakdown, and dispersion of spherical metal particles over the substrate.

Mitochondrial network expansion and dynamic redistribution during islet morphogenesis in zebrafish larvae.

Mitochondria, organelles critical for energy production, modify their shape and location in response to developmental state and metabolic demands. Mitochondria are altered in diabetes, but the mechanistic basis is poorly defined, due to difficulties in assessing mitochondria within an intact organism. Here, we use invivo imaging in transparent zebrafish larvae to demonstrate filamentous, interconnected mitochondrial networks within islet cells. Mitochondrial movements highly resemble what has been reported for human islet cells invitro, showing conservation in behaviour across species and cellular context. During islet development, mitochondrial content increases with emergence of cell motility, and mitochondria disperse within fine protrusions. Overall, this work presents quantitative analysis of mitochondria within their native environment and provides insights into mitochondrial behaviour during organogenesis.

Creation of 3 D Models from SEM Images of Fine Protrusions Formed by Sputter-Etching

Creation of 3 D Models from SEM Images of Fine Protrusions Formed by Sputter-Etching

Formation of Fine Protrusions by Sputter Etching of Stainless Steels and Evaluation of Gripping Ability of Fiber Sheets

Argon ion sputter etching of AISI type 420 stainless steels was carried out at a power of 250 W for 14.4 ks to form cone-shaped protrusions with bottom diameters of 10–20 µm by using a radio-frequency magnetron sputter apparatus. The sputter etching was also applied to AISI type 316 stainless steel at 250 W for 10.8 ks, and fine column-shaped protrusions with diameters smaller than 500 nm were formed. In addition, plasma-nitriding was applied to the protrusions of type 420 steel using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50 W for 1.8 ks. The gripping ability of protrusions was measured by friction tests for three types of fiber sheets. For a cotton cloth, the friction coefficients of the as-sputter-etched and plasma-nitrided type 420 steel specimens were 1.3 and 1.7 at a nominal compressive stress of 0.8 kPa, and that of the as-sputter-etched type 316 steel specimen was 1.0. These are much larger than 0.8 and 0.5 of the specimens polished with #100 emery paper and buff-polished with alumina powders. Also for microfiber and polyester fiber sheets, the specimen with protrusions showed a higher gripping ability than those of the mechanically polished specimens. The reason for the large gripping ability of protrusion specimens is due to piercing of the protrusions between and into weaving yarns.

A Curvature-Enhanced Random Walker Segmentation Method for Detailed Capture of 3D Cell Surface Membranes.

High-resolution 3D microscopy is a fast advancing field and requires new techniques in image analysis to handle these new datasets. In this work, we focus on detailed 3D segmentation of Dictyostelium cells undergoing macropinocytosis captured on an iSPIM microscope. We propose a novel random walker-based method with a curvature-based enhancement term, with the aim of capturing fine protrusions, such as filopodia and deep invaginations, such as macropinocytotic cups, on the cell surface. We tested our method on both real and synthetic 3D image volumes, demonstrating that the inclusion of the curvature enhancement term can improve the segmentation of the aforementioned features. We show that our method performs better than other state of the art segmentation methods in 3D images of Dictyostelium cells, and performs competitively against CNN-based methods in two Cell Tracking Challenge datasets, demonstrating the ability to obtain accurate segmentations without the requirement of large training datasets. We also present an automated seeding method for microscopy data, which, combined with the curvature-enhanced random walker method, enables the segmentation of large time series with minimal input from the experimenter.

Software development for modeling irregular fine protrusions formed by sputter etching

Irregular fine protrusions formed on the surface of a mechanical part through biomimetic technology can enhance the part’s properties, including tribology, self-cleaning, and light absorption. However, underlying principles for the formation of fine protrusions according to the requirements of their shapes, sizes, and material distributions have not been studied sufficiently. This paper presents the software development for modeling irregular fine protrusions, which is essential for the simulation, experimentation, and analysis of fine protrusions formed by sputter etching.

Optogenetic Interneuron Stimulation and Calcium Imaging in Astrocytes.

In brain networks, neurons are constantly involved in a dynamic interaction with the other cell populations and, particularly, with astrocytes, the most abundant glial cells in the brain. Astrocytes respond to neurotransmitters with Ca2+ elevations which represent a key event in the modulation of local brain circuits played by these glial cells. Due to technical limitations, the study of Ca2+ signal dynamics in astrocytes has focused for decades almost exclusively on somatic and perisomatic regions. Accordingly, Ca2+ signal in astrocytic fine protrusions, which are in close contact with the synapse, has been poorly investigated. Over the last years, the diffusion of novel tools such as the viral vector gene delivery of genetically encoded Ca2+ indicators (GECI), the optogenetics, and multiphoton laser scanning microscopy has boosted significantly our capability to study astrocytic Ca2+ signals in the different subcellular compartments. Here we report a protocol that combines these techniques to study astrocyte Ca2+ signaling in response to somatostatin (SST)-expressing interneurons, one of the main classes of GABAergic inhibitory interneurons.

Gripping and frictional-conveying characteristics of fine protrusions formed by sputter-etching of stainless steels

Gripping and frictional-conveying characteristics of fine protrusions formed by sputter-etching of stainless steels

Live cell near-field optical imaging and voltage sensing with ultrasensitive force control.

Force controlled optical imaging of membranes of living cells is demonstrated. Such imaging has been extended to image membrane potential changes to demonstrate that live cell imaging has been achieved. To accomplish this advance, limitations inherent in atomic force microscopy (AFM) since its inception in 1986 [G. Binnig, C. F. Quate, and C. Gerber, "Atomic Force Microscope," Phys. Rev. Lett. 56, 930-933 (1986).] had to be overcome. The advances allow for live cell imaging of a whole genre of functional biological imaging with stiff (1-10N/m) scanned probe imaging cantilevers. Even topographic imaging of fine cell protrusions, such as microvilli, has been accomplished with such cantilevers. Similar topographic imaging has only recently been demonstrated with the standard soft (0.05N/m) cantilevers that are generally required for live cell imaging. The progress reported here demonstrates both ultrasensitive AFM (~100pN), capable of topographic imaging of even microvilli protruding from cell membranes and new functional applications that should have a significant impact on optical and other approaches in biological imaging of living systems and ultrasoft materials.

工業用純チタンのスパッタエッチングによる微細突起物の形成

工業用純チタンのスパッタエッチングによる微細突起物の形成

Effect of plasma nitriding on the strength of fine protrusions formed by sputter etching of AISI type 420 stainless steel

Argon ion sputter-etching of AISI type 420 martensitic stainless steel was carried out to form conical protrusions with bottom diameter of 10–30μm on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions with various mixing rate of nitrogen and argon gas. The shape of the protrusions was examined by using a scanning electron microscope, and the nitrides formed on the protrusions were identified by means of an X-ray diffraction analysis. Micro-Vickers hardness tests and nano-scratch tests were used to evaluate the deformation resistance of the protrusions. By plasma-nitriding at a nitrogen pressure of 130Pa and a nitriding power of 50W, about 1.3 times larger indentation resistance than that of the as-sputter-etched protrusions was obtained after a long nitriding time of 14ks. When plasma-nitriding was carried out at a lower nitrogen pressure of 1.2Pa and a higher nitriding power of 200W for 7.2ks, indentation and scratch resistances of the protrusions largely increased to the values almost three times as large as those of the as-sputter-etched protrusions. However, the protrusions were brittle due to the formation of thick nitride layers and the sharpness of the protrusions was lost. Reduction of the nitriding power to 50W recovered the sharpness with small amount of surface nitride layer, but the indentation resistances were only 1.4 times larger values than those of the as-sputter-etched protrusions. On the other hand, plasma-nitriding using a mixture of nitrogen gas of 0.53Pa and argon gas of 0.67Pa at the power of 50W produced almost twice larger indentation and scratch resistances than those of the as-sputter-etched protrusions within a short nitriding time of 1.8ks, retaining the sharpness of protrusions without forming brittle nitrided layers.

Enhancement of Visible Light Absorbance and Hydrophobicity by Sputter-Coating of PTFE onto Fine Protrusions Formed by Sputter-Etching of Steels

Enhancement of Visible Light Absorbance and Hydrophobicity by Sputter-Coating of PTFE onto Fine Protrusions Formed by Sputter-Etching of Steels

鋼および銅合金のスパッタエッチングによって形成した微細突起物の可視光線および赤外線吸収特性

鋼および銅合金のスパッタエッチングによって形成した微細突起物の可視光線および赤外線吸収特性

Superhydrophobicity produced by vapor deposition of a hydrophobic layer onto fine protrusions formed by sputter-etching of steels

Argon ion sputter-etching was applied to W–Mo–Cr–V high speed steel, Cr–Mo–V die steel, and type 304 and 316 austenitic stainless steels. Vapor-deposition of the polyethylene (PE) or 1H, 1H, 2H, 2H, -Perfluorodecyltriethoxysilane (PFDS) was carried out on the sputter-etched surface. The hydrophobicity was evaluated by measuring the contact angle (CA) of a water droplet on the surface. The sputter-etching formed fine and dense pillar- or cone-shaped protrusions with a diameter of 100nm to 1μm on the tool steels and the type 316 steel but cone-shaped protrusions with a diameter of more than 1μm on the type 304 steel. The surfaces of all the steels just after the sputter-etching revealed CAs smaller than 4.5°, or superhydrophilicity. On the other hand, all the steels that were sputter-etched and vapor-deposited with PE or PFDS produced CAs of more than 150°, or superhydrophobicity, except that the CA of the type 304 steel with micron-sized protrusions was 146°. The adhesion of the PFDS layer to the protrusions is much stronger than the PE layer, i.e. it is difficult to remove the PFDS layer by heating at 473K and ultrasonic cleaning in acetone.

Vibration Analysis of Original Shape Quartz Resonator for High Quality Factor Realization

AT-cut quartz resonators are widely used as timing devices in computers, mobile information, and communication tools, etc. Recently, quartz resonators have been applied to highly sensitive devices. To improve frequency stability, AT-cut quartz resonators must have an excellent temperature characteristic and high quality (Q) factor. Energy trapping and spurious mode coupling strongly affect the performance of resonators, and both parameters are determined by the shape of the resonator. As for achieving a higher Q, the most effective technique is to process the quartz cross-sectional shape into a plano-convex or bi-convex shape. However, it is difficult to manufacture a convex shape on the surface of a quartz wafer. For this reason, we propose an equivalent plano-convex shape, which was realized by arranging fine protrusions on the surface of quartz. In addition, the optimization of the original resonator shape has been discussed.

Live Imaging of Cell Motility and Actin Cytoskeleton of Individual Neurons and Neural Crest Cells in Zebrafish Embryos

The zebrafish is an ideal model for imaging cell behaviors during development in vivo. Zebrafish embryos are externally fertilized and thus easily accessible at all stages of development. Moreover, their optical clarity allows high resolution imaging of cell and molecular dynamics in the natural environment of the intact embryo. We are using a live imaging approach to analyze cell behaviors during neural crest cell migration and the outgrowth and guidance of neuronal axons.Live imaging is particularly useful for understanding mechanisms that regulate cell motility processes. To visualize details of cell motility, such as protrusive activity and molecular dynamics, it is advantageous to label individual cells. In zebrafish, plasmid DNA injection yields a transient mosaic expression pattern and offers distinct benefits over other cell labeling methods. For example, transgenic lines often label entire cell populations and thus may obscure visualization of the fine protrusions (or changes in molecular distribution) in a single cell. In addition, injection of DNA at the one-cell stage is less invasive and more precise than dye injections at later stages.Here we describe a method for labeling individual developing neurons or neural crest cells and imaging their behavior in vivo. We inject plasmid DNA into 1-cell stage embryos, which results in mosaic transgene expression. The vectors contain cell-specific promoters that drive expression of a gene of interest in a subset of sensory neurons or neural crest cells. We provide examples of cells labeled with membrane targeted GFP or with a biosensor probe that allows visualization of F-actin in living cells1.Erica Andersen, Namrata Asuri, and Matthew Clay contributed equally to this work.

Live Imaging of Cell Motility and Actin Cytoskeleton of Individual Neurons and Neural Crest Cells in Zebrafish Embryos

The zebrafish is an ideal model for imaging cell behaviors during development in vivo. Zebrafish embryos are externally fertilized and thus easily accessible at all stages of development. Moreover, their optical clarity allows high resolution imaging of cell and molecular dynamics in the natural environment of the intact embryo. We are using a live imaging approach to analyze cell behaviors during neural crest cell migration and the outgrowth and guidance of neuronal axons. Live imaging is particularly useful for understanding mechanisms that regulate cell motility processes. To visualize details of cell motility, such as protrusive activity and molecular dynamics, it is advantageous to label individual cells. In zebrafish, plasmid DNA injection yields a transient mosaic expression pattern and offers distinct benefits over other cell labeling methods. For example, transgenic lines often label entire cell populations and thus may obscure visualization of the fine protrusions (or changes in molecular distribution) in a single cell. In addition, injection of DNA at the one-cell stage is less invasive and more precise than dye injections at later stages. Here we describe a method for labeling individual developing neurons or neural crest cells and imaging their behavior in vivo. We inject plasmid DNA into 1-cell stage embryos, which results in mosaic transgene expression. The vectors contain cell-specific promoters that drive expression of a gene of interest in a subset of sensory neurons or neural crest cells. We provide examples of cells labeled with membrane targeted GFP or with a biosensor probe that allows visualization of F-actin in living cells1. Erica Andersen, Namrata Asuri, and Matthew Clay contributed equally to this work.

Deformation Characteristics of Fine Protrusions Formed by Sputter-Etching of Stainless Steels

Sputter-etching was applied to type 303, 304, 430 and 420 stainless steels to form conical or ring-shaped protrusions on the surface, and the tensile test of the substrate with protrusions, the press and scratch tests of protrusions were carried out. The tensile test shows that the conical protrusion is ductile, and the delamination and dropping out of the protrusions from substrate never occur before fracture of the substrate. The press test of the protrusions reveals that the conical protrusion is so strong to form deep hole on the counter rod of aluminum alloy although the tip of the protrusion is flattened. The scratch test of the surface with conical protrusions shows a large change of friction force with increasing scratch distance, whereas relatively small change of friction force for ring-shaped protrusions due to a smaller height and a narrow space between each ring wall. The maximum scratch force for a typical conical protrusion is about 40mN.

Perifollicular protrusions - mid-dermal elastolysis

Mid-dermal elastolysis is a rare peculiar entity clinically characterized by fine wrinkles and perifollicular protrusions that give the skin an aged or peau d'orange appearance. The histopathologic correlate is a bandlike loss of elastic tissue within the mid-dermis.We present a typical case with prominent perifollicular protrusions.

Chemical Mechanical Polishing for Oxygen Free Copper with Manganese Oxide Abrasives

The purpose of this study is to make clear the polishing characteristics of the manganese oxide slurry for wire material of Cu. To examine the polishing characteristics of the manganese oxide slurry, a series of polishing experiments for oxygen free copper have been carried out by using MnO2, Mn2O3 and Al2O3 as abrasive grains and polishing properties have been discussed. As a result, the best result among three kinds of slurries is obtained in polishing with Mn2O3 slurry at the viewpoints of the stock removal and surface roughness. Furthermore polished surfaces have been analyzed using SEM and atomic force microscope. While a large number of mechanical scratches are observed in the polished surface with Al2O3 slurry, the polished surfaces with manganese oxide slurries are covered with fine protrusions. It seems that the fine protrusions result from interaction between mechanical and chemical effects.