Lamellae Layers Research Articles

Systematic in situ hydration neutron reflectometry study on Nafion thin films.

Reported herein is a neutron reflectometry (NR) study on hydrated Nafion thin films (∼30 nm) on a silicon substrate with native oxide. The Nafion morphology is investigated systematically across the whole relative humidity range using both H2O and D2O vapours to enable a comparative study. By utilising this systematic approach two key results have been obtained. The first is that by leveraging the strong positive scattering signal from the D2O vapour, a complete and systematic water adsorption isotherm (Type II) for a Nafion thin film is produced. Utilising the slight negative scattering signal of the H2O enabled the quantification of the hydration dependent evolution of the formation of Nafion/water lamellae near the substrate surface. The number of lamellae layers increases continuously with hydration, and does not form abruptly. We also report the effects of swelling on the thin films across the relative humidity ranges. The work reported should prove useful in quantifying other hydration dependent properties of Nafion thin films such as conductivity and understanding Nafion/semiconductor based devices, as well as showcasing a NR methodology for other hydrophilic polymers.

Comparison Study of Optical Sensing Property of Gratings with and without Lamellae Layers

Local plasmatic resonance existing around nanoscale metallic structures is closely related to the refractive index of the surrounding media. Gold Lamellae layers embedded in gratings are ideal to populate the plasmatic resonances locally with much higher concentration than the simple gratings, leading to enhanced sensitivity to the testing materials. Based on our earlier success in replicating dielectric lamellae layers, this paper reports our further work in converting the dielectric lamellae layers into gold ones and the study of their optical property as refractive index sensors. To prove the local surface plasmatic resonance be responsible for absorbing the light, the gratings without the lamellae layer were also tested for comparison. Both numerical simulation using the finite difference time domain method and optical measurements have demonstrated the enhanced sensitivity by the gratings with lamellae layers, although structural optimization is still needed. With the further improvement in both structural configuration, material and nanofabrication technique, it is believed that the proposed lamellae layers should be a promising candidate for highly sensitive environmental sensors.

Ultrastructure of the fertilized egg envelopes in Hemigrammus erythrozonus, Characidae, Teleostei

We examined the morphology and ultrastructures of fertilized egg envelopes of glowlight tetra (Hemigrammus erythrozonus) belong to Characidae using light and electron microscopes.The fertilized eggs were spherical, transparent, demersal, adhesive, and have no oil droplet. The perivitelline space was well-developed and the micropyle was surrounded by 15–20 uplifted lines of egg envelope in a spoke like pattern. The outer surface of egg envelope was rough side with grooves. Also, the total thickness of the fertilized egg envelope was about 2.1–2.3 μm, and the fertilized egg envelope consisted of two layers, an outer adhesive electron-dense layer with grooves and three feather-like lamellae layers. Collectively, these morphological characteristics of fertilized egg and micropyle with spoke-like structure showed family Characidae specificity, and ultrastructures of outer surface and section of fertilized egg envelope showed species specificity.

Hierarchical Structure Including Nanoscale Passages By Using Wet-Etching of Nickel Thin Films in Lamellae Layers for Bio-Sensors Applications

In recent years, research for surface hierarchical structures for chemical sensor and bio-sensor devices applications has been highlighted owing to their relatively large ratio of surface-area compared to the volume. Especially, the hierarchical micro-nanostructures (organization of the nanostructure within the microstructure) including nanoscale passages have been intensively studied, because nanoscale passages are necessary for single-molecule DNA sequencing. In order to realize a hierarchical micro-nanostructure, the fabrication process for micro- and nano-scale structures should be applied together, controlling each pattern size precisely. Therefore, the properties of lateral Ni film etching by TFB etchant at room temperature were investigated by using samples with patterned lamellae layers consist of Ni, Al2O3, and SiO2 for fabricating hierarchical structures for the fabrication of hierarchical structure including nanoscale passages. Lateral etching length was increased with increasing etching time, despite of the difficult passage through nanoscale passage in lamellae layers. However, higher etching rate (2.1 nm/s) was observed in lower Ni film, which has contact with SiO2 and Al2O3 layers, compared to that (1.6 nm/s) of upper Ni film, which has contact with only Al2O3, due to stronger wetting property of SiO2, inducing easier penetration of etchant into nanoscale passage between surrounding layers. Moreover, the influence of Ni film thickness on lateral etching characteristics was also investigated. In this presentation, the fabrication process based on lateral Ni film etching in lamellae layers by liquid etchant at room temperature will be presented systematically for bio-sensor applications.

Nanofabrication and coloration study of artificial Morpho butterfly wings with aligned lamellae layers.

The bright and iridescent blue color from Morpho butterfly wings has attracted worldwide attentions to explore its mysterious nature for long time. Although the physics of structural color by the nanophotonic structures built on the wing scales has been well established, replications of the wing structure by standard top-down lithography still remains a challenge. This paper reports a technical breakthrough to mimic the blue color of Morpho butterfly wings, by developing a novel nanofabrication process, based on electron beam lithography combined with alternate PMMA/LOR development/dissolution, for photonic structures with aligned lamellae multilayers in colorless polymers. The relationship between the coloration and geometric dimensions as well as shapes is systematically analyzed by solving Maxwell’s Equations with a finite domain time difference simulator. Careful characterization of the mimicked blue by spectral measurements under both normal and oblique angles are carried out. Structural color in blue reflected by the fabricated wing scales, is demonstrated and further extended to green as an application exercise of the new technique. The effects of the regularity in the replicas on coloration are analyzed. In principle, this approach establishes a starting point for mimicking structural colors beyond the blue in Morpho butterfly wings.

The Effect of Static Stretch on Elastin Degradation in Arteries

Previously we have shown that gradual changes in the structure of elastin during an elastase treatment can lead to important transition stages in the mechanical behavior of arteries [1]. However, in vivo arteries are constantly being loaded due to systolic and diastolic pressures and so understanding the effects of loading on the enzymatic degradation of elastin in arteries is important. With biaxial tensile testing, we measured the mechanical behavior of porcine thoracic aortas digested with a mild solution of purified elastase (5 U/mL) in the presence of a static stretch. Arterial mechanical properties and biochemical composition were analyzed to assess the effects of mechanical stretch on elastin degradation. As elastin is being removed, the dimensions of the artery increase by more than 20% in both the longitude and circumference directions. Elastin assays indicate a faster rate of degradation when stretch was present during the digestion. A simple exponential decay fitting confirms the time constant for digestion with stretch (0.11±0.04 h−1) is almost twice that of digestion without stretch (0.069±0.028 h−1). The transition from J-shaped to S-shaped stress vs. strain behavior in the longitudinal direction generally occurs when elastin content is reduced by about 60%. Multiphoton image analysis confirms the removal/fragmentation of elastin and also shows that the collagen fibers are closely intertwined with the elastin lamellae in the medial layer. After removal of elastin, the collagen fibers are no longer constrained and become disordered. Release of amorphous elastin during the fragmentation of the lamellae layers is observed and provides insights into the process of elastin degradation. Overall this study reveals several interesting microstructural changes in the extracellular matrix that could explain the resulting mechanical behavior of arteries with elastin degradation.

Theoretical and experimental analysis of the structural pattern responsible for the iridescence of Morpho butterflies

Morpho butterflies are well-known for their iridescence originating from nanostructures in the scales of their wings. These optical active structures integrate three design principles leading to the wide angle reflection: alternating lamellae layers, "Christmas tree" like shape, and offsets between neighboring ridges. We study their individual effects rigorously by 2D FEM simulations of the nanostructures of the Morpho sulkowskyi butterfly and show how the reflection spectrum can be controlled by the design of the nanostructures. The width of the spectrum is broad (≈ 90 nm) for alternating lamellae layers (or "brunches") of the structure while the "Christmas tree" pattern together with a height offset between neighboring ridges reduces the directionality of the reflectance. Furthermore, we fabricated the simulated structures by e-beam lithography. The resulting samples mimicked all important optical features of the original Morpho butterfly scales and feature the intense blue iridescence with a wide angular range of reflection.

Preparation and thermoelectric properties of quaternary bismuth telluride–indium selenide compound

Quaternary In–Se–Bi–Te compounds (7.5Bi 2Te 3–In 2Se 3 and 7.5Bi 2Te 3–In 4Se 3) were prepared by water quenching and annealing, and the microstructures and thermoelectric properties were investigated. These materials were solidified to near-eutectic compositions in order to obtain micro-scale heterointerfaces. The formation of sub-micrometer-scale lamellae layers of Bi 2Te 3 and In–Se–Te compounds was observed. Through quenching, the 7.5Bi 2Te 3–In 2Se 3 consisted of a Bi 2Te 3 and In–Se–Te compound, while the 7.5Bi 2Te 3–In 4Se 3 was composed of Bi 2Te 3, BiTe, and In 4Se 3 and In–Se–Te. Both the microstructure and the constituent phases changed after annealing. The reduction of thermal conductivities, as compared to that of bulk Bi 2Te 3, was confirmed. This result can be attributed to the increased number of phase boundary areas. The size of the decomposed phase could be controlled by changing the parameters of the annealing process, which could further decrease the thermal conductivity.

Perforated Lamellae Morphology in Novel P2VP(PDMS-b-PI-b-PS)2 3-Miktoarm Star Quarterpolymer

The melt morphology of a novel P2VP(PDMS-b-PI-b-PS)2 3-miktoarm star quarterpolymer is investigated. The melt morphology is determined using rheology and small-angle neutron and X-ray scattering data in conjunction with dissipative particle dynamics simulations of a model molecule matching the volume fractions of the experimental system. The simulations are used to interpret the scattering data and identify the melt morphology as a new perforated lamellae structure. In this structure the P2VP forms hexagonally perforated lamellae containing close-packed protrusions of PS connecting adjacent lamellae layers of PS. The PI part forms a lining between the P2VP and PS domains constrained by the molecular architecture.

Is there delamination wear in polyurethane?

Delamination wear is found in the literature of metals, ceramics and composite materials involving layers of different polymers. In the tribological investigations on polymers, the phenomenon of delamination in polyurethane has not generally been cited. This work focuses the damage mechanism of delamination noticed in flat surfaces of thermoplastic polyurethane elastomer (TPU), when sliding against rotating surfaces. A sliding testing rig was conduced using an innovated counterface, based on the taxionomy, proposed by Briscoe for polymer wear mechanisms. It was constituted by a cylindrical metallic axis, manufactured using AISI 1045 steel with seven angular protuberances of different contact angles (15o, 45o, 75o, 105o, 135o, 165o and 180o), instead of conventional sphere. This geometry developed in TPU distinct damage modes during sliding tests. Worn surface examinations were conducted using scanning electron microscope (SEM). The morphologies of the wear sheet detected by SEM suggest that two different processes of damage may have originated the delamination. In one process, associated with a shakedown mechanism as defined by Johnson, every located stress state can be associated with the contact pressure, the traction coefficient and TPU cumulative response of yield surface and elastic sub-surfaces resulting in different lamellae layers. In another process, the creation of wear lamellae occurred by shearing and squeezing a small amount of material following a large number of asperities that have crossed each point on the surface, as suggested originally by Suh. The experiment provided, moreover, wear mechanisms well known as prow formation, ploughing, fatigue (wave formation), melting and tearing.

Submicroscopic structure and development of the chloroplasts of Cibotium chamissoi

Embryonic and mature leaves of Cibotium chamissoi were used for the study of the fine structure and the development of chloroplasts. The chloroplasts of Cibotium are spherical in cross-section, about from 0.5 to 0.8 μ in diameter, and more or less elliptical in outline, when cut obliquely. They are bounded by a well-defined outer membrane. The grana are distributed more or less uniformly throughout the chloroplast, except in those instances in which an irregular peripheral zone is devoid of grana. The grana are randomly oriented between the stroma lamellae. The thickness of the lamellae within the grana was measured about 95 å. At the boundary of the grana, an osmiophilic substance is present. In addition to this substance, relatively large osmiophilic globules also occur in the stroma. From various stages of developing leaves, the following stages of developing chloroplasts were found: 1. (a) The first ultrastructure to be seen within the proplastids are vesicles. In most cases they also contain osmiophilic globules. A dense margin indicates a membrane. 2. (b) The lamellae layers are formed locally by the fusion of the vesicles. 3. (c) The number of lamellae layers increased with size of the chloroplasts. 4. (d) Within the plastids, lamellae appear in bundles, which indicate the grana formation. Lamellated grana are connected by the stroma lamellae, which are less numerous.

Fixation of nitrogen by alumina and carbon: Tucker and Read, ( Amer. Electrochem. Soc. Trans., xxii, 57.)

Delamination wear is found in the literature of metals, ceramics and composite materials involving layers of different polymers. In the tribological investigations on polymers, the phenomenon of delamination in polyurethane has not generally been cited. This work focuses the damage mechanism of delamination noticed in flat surfaces of thermoplastic polyurethane elastomer (TPU), when sliding against rotating surfaces. A sliding testing rig was conduced using an innovated counterface, based on the taxionomy, proposed by Briscoe for polymer wear mechanisms. It was constituted by a cylindrical metallic axis, manufactured using AISI 1045 steel with seven angular protuberances of different contact angles (15o, 45o, 75o, 105o, 135o, 165o and 180o), instead of conventional sphere. This geometry developed in TPU distinct damage modes during sliding tests. Worn surface examinations were conducted using scanning electron microscope (SEM). The morphologies of the wear sheet detected by SEM suggest that two different processes of damage may have originated the delamination. In one process, associated with a shakedown mechanism as defined by Johnson, every located stress state can be associated with the contact pressure, the traction coefficient and TPU cumulative response of yield surface and elastic sub-surfaces resulting in different lamellae layers. In another process, the creation of wear lamellae occurred by shearing and squeezing a small amount of material following a large number of asperities that have crossed each point on the surface, as suggested originally by Suh. The experiment provided, moreover, wear mechanisms well known as prow formation, ploughing, fatigue (wave formation), melting and tearing.