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While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be capable of achieving turbulent flow control and drag reduction, sharkskin-inspired “riblets” have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and modeling of “fresh” denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold: (1) 2D imaging of lubricated sharkskin in a wet state by means of a “nano-suit” technique with a Field-Emission Scanning Electron Microscope (FE-SEM); (2) 3D structures of sharkskin denticles with a micro-focus X-ray CT; and (3) single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges (herein termed “non-uniform grooves”) with Angles Of Inclination (AOI) ranging over 20°–32°. Hydrodynamics associated with the unique five-ridge denticles were then investigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.

In UV nanoimprinting, the selection of monomers suitable for sub-15 nm patterning is difficult because the filling behavior of resin at this scale still remains scientifically unclear. We demonstrate sub-15 nm patterning by UV nanoimprinting using silica molds with 20, 15, and 7 nm diameter holes; however, the 7 nm diameter pillar patterns were not fabricated using hydroxy-containing monomers. The filling behavior into silica holes of around 10 nm depended on the chemical structure of the monomers. Resonance shear measurements revealed the following: (1) The viscosities of hydroxy-containing monomers confined between chlorodimethyl(3,3,3-trifluoropropyl)silane (FAS3-Cl)-modified surfaces began to increase at distances shorter than those of the monomers between unmodified surfaces. (2) The monomers confined between tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane-modified surfaces were squeezed out when the surface-surface distance decreased at less than 7 nm. The measured viscosities between the FAS3-Cl-modified silica surfaces were correlated with the insufficient filling behavior into the silica holes of around 10 nm in UV nanoimprinting. Contact angle measurements provided an additional insight that a higher wettability of the monomers onto the antisticking chemisorbed monolayers resulted in imprinted patterns with higher aspect ratios. Considering the increase in the monomer viscosity in the nanospace and the wettability of monomers onto chemisorbed monolayers, we concluded that the monomer showing low viscosity under confinement and high wettability onto the mold surface was suitable for single-digit nanometer UV nanoimprinting.

The salp Thalia rhomboides is distributed in the shallow depths during the day, and is thus at increased risk of predation by visual predators and from the damaging effects of ultraviolet (UV) radiation compared with species distributed in deeper layers in the daytime. The integument (tunic) of T. rhomboides may have adaptive optical properties, but the absorption spectra of the unfixed tunic demonstrate that the tunic transmits UV as well as visible light, indicating that the tunic is not an effective barrier against UV radiation. Ultrastructural observation revealed that the surface of the tunic cuticle is covered in a nipple array consisting of hemispherical protuberances approximately 40 and 30 nm in diameter in solitary and aggregate zooids, respectively. Simulation of light reflection of a nipple array using rigorous coupled wave analysis (RCWA) indicated that the reflection is slightly lower for the nipple array than for a flat surface at high angles of incidence (θ > 80°). This result supports the idea that the nipple array serves to make the salp less visible. The simulation also indicated that the height and distribution of the salp nipple array do not have an optimal structure for causing an antireflection effect. A mechanical restriction might exist on the structures, and the nipple array could also serve another function. The size and distribution of nipples may be controlled by the need to meet the complex requirements of multiple essential functions.

The fluidity of the resin for the nanoimprint lithography was investigated in a quasi-2D space by the shear resonance measurement, which enables us to measure the viscous property of the resin confined in a nanometer gap between mica surfaces. With this technique, we could observe that the resin fluidity was enhanced by the addition of the fluorine-containing monomer. The fluidity of the resin with the fluorine-containing monomer was maintained until the distance between mica surfaces became smaller than 15 nm, wheras the resin without the fluorine-containing monomer started losing its fluidity when the distance became 30 nm. Two reasons possibly explain the result; (i) the interaction between the resin and mica was reduced by the existence of the fluorine-containing segregated layer at the interface, and (ii) the reduction in viscosity took place by the addition of the fluorine-containing monomer that reduced the degree of chain entanglement in the resin because of its small intermolecular interaction force. The effect of the length of the perfluoroalkyl chain in the fluorine-containing monomer is also discussed.

Nanoimprint has been expanding to various industrial fields, such as optical device, semiconductor and bio-devices. High-throughput machine and process are necessary for industrialization of thermal nanoimprint products. Conventional parallel press method needs long tact time because of the long heating and cooling process in thermal nanoimprint. We proposed the sheet nanoimprint method which uses the newly developed belt nanomold. The continuous process became possible by using the belt nanomold and we demonstrated the 200- and 25-nm dots formation onto over 10-m-long films with 10-mm/s film speed. For bio-application, we demonstrated the spheroid formation of HeLa and hepatic cells on nanoimprinted pillar structures. The cells were easy to coalesce on the pillar structure and the spheroids were formed. Uniform-size spheroids were formed at predefined positions by using micro-incubator structure.

A release layer for nanoimprint lithography was formed on atomically flat Si(111) terraces to investigate its surface morphology and degradation behavior due to imprinting. The adhesive nature between the layers and a polystyrene colloid probe was also evaluated. Three types of release layers (silicone, fluoro-oligomer, and perfluoropolyether) were formed on mildly oxidized Si(111) substrates that retained a flat terrace structure. All the layers were sufficiently thin and uniform to show the flat terrace structure of the Si(111) substrates. These release layers showed different degradation behaviors toward thermal nanoimprint lithography and UV-photocure nanoimprint lithography cycles as elucidated by x-ray photoelectron spectroscopy, atomic force microscopy, and adhesion force measurements. The perfluoropolyether exhibited better durability against nanoimprint cycles due to the presence of free molecules not bound to the surface. This study includes a detailed discussion of the degradation mechanisms of...

Post-annealing characteristics of in situ B-doped poly-SiGe films have been investigated. Thermal stability of substitutional B atoms at a supersaturated concentration was significantly improved by Ge doping, for example, the stability at 800°C for poly-Si0.6Ge0.4 films was nine times as high as that for poly-Si films. Both fast and slow processes exist for the deactivation of B. The fast process was due to movement of B atoms from substitutional to interstitial sites, enhanced by a local strain induced by the difference in atomic radii between Si and B atoms, and the slow process was due to trapping of B at grain boundaries during grain growth. The mechanism of the improved thermal stability of B atoms is discussed on the basis of local strain compensation by Ge atoms.

Thermal stability of B atoms in in situ doped poly-SiGe films has been investigated. After annealing at 600–900 °C, the carrier concentration in the films decreased with increasing annealing time, which was due to transition from the super-saturated concentration of B for as-deposited films to the solid solubility at the annealing temperature. Thermal stability of B atoms was significantly improved by Ge doping, e.g. the stability in poly-Si 0.6 Ge 0.4 films was four times as high as that in poly-Si films. The deactivation process of B atoms could be separated into the fast and slow processes. The time constants for both processes did not depend on the Ge fraction, while the ratio of deactivated B atoms in the fast process to those in the slow process decreased by Ge doping. The two-state model has been proposed, and explained the improved thermal stability of B atoms by Ge doping.

The nipple array is a submicrometre-scale structure found on the cuticle surfaces of various invertebrate taxa. Corneal nipples are an antiglare surface in nocturnal insects, but the functional significance of the nipple array has not been experimentally investigated for aquatic organisms. Using nanopillar sheets as a mimetic model of the nipple array, we demonstrated that significantly fewer bubbles adhered to the nanopillar surface versus a flat surface when the sheets were hydrophilic. Many more bubbles adhered to the hydrophobic surface than the hydrophilic surfaces. Bubbles on the body surface may cause buoyancy problems, movement interference and water flow occlusion. Here, bubble repellence is proposed as a function of the hydrophilic nipple array in aquatic invertebrates and its properties are considered based on bubble adhesion energy.

The analytical expressions for thickness and δ (δ=1-refractive index) of an interface layer from x-ray reflectivity measurements are obtained for an epitaxial layer/interface layer/Si substrate system. The contaminated interface layer between the defective epitaxial layer and Si substrate is detected by the x-ray reflectivity. The stacking fault density (SFD) in the epitaxial layer is correlated with the δ of the interface layer. There is a linear relation between the δ and oxygen concentration of the interface layers. The δ of the interface layer is less than that of Si which is mainly due to oxygen in the interface layer. The thicknesses of the interface layers are about 1.4 nm and they do not correlate with the SFDs in the epitaxial layer

Background In idiopathic Parkinson's disease (PD) the clinical features are heterogeneous and include different predominant symptoms. The aim of the present study was to determine the relationship between subregional aromatic l-amino acid decarboxylase (AADC) activity in the striatum and the cardinal motor symptoms of PD using high-resolution positron emission tomography (PET) with an AADC tracer, 6-[18F]fluoro-ʟ-m-tyrosine (FMT). Methods We assessed 101 patients with PD and 19 healthy volunteers. PD was diagnosed based on the UK Brain Bank criteria by two experts on movement disorders. Motor symptoms were measured with the Unified Parkinson's Disease Rating Scale (UPDRS). FMT uptake in the subregions of the striatum was analyzed using semi-automated software for region-of-interest demarcation on co-registered magnetic resonance images. Results In all PD patients, FMT uptake was decreased in the posterior putamen regardless of predominant motor symptoms and disease duration. Smaller uptake values were found in the putamen contralateral to the side with more affected limbs. The severity of bradykinesia, rigidity, and axial symptoms was correlated with the decrease of FMT uptake in the putamen, particularly in the anterior part. No significant correlation was observed between tremors and FMT uptake. Conclusions Decrease of FMT uptake in the posterior putamen appears to be most sensitive in mild PD and uptake in the anterior putamen may reflect the severity of main motor symptoms, except for tremor.

This paper investigates a replication process using the organic-inorganic hybrid material. The condition of heat treatment was determined on the basis of the hardness and transmission measurements. 100 repeated imprints were demonstrated using the replicated mold and achieved good fidelity.

The nanoimprint technology is attractive for the fabrication of nano-scale structures in view of cost and mass production. There are several points for the industrial applications such as pattern formation area, resolution, residual layer thickness, precise control of pattern transfer, lifetime of mold, alignment and so on. A thermal nanoimprint system, which can imprint fine dots on a 300 mm diameter wafer in a single step, is developed. The narrow pith patterns for future storage and IT devices are formed on a polymer layer. A high-aspect nanoprint (Hi-NP) technology forms polymer nanopillars with high aspect ratio. The nanopillars are applied to a bio-chip for the fluorescence immunoassay. The chip is effective in the enhancement of the fluorescence intensities, since the nanopillars enlarge the surface area.

Nanopillar sheets were fabricated with high-aspect ratio structures with a diameter of 160-1,000 nm and a height of 1 mum by nanoimprinting. The suitability of nanopillar sheets as a new type of cell culture dish was examined by studying the behavior of HeLa cells cultured on the sheets using light microscopy, scanning electron microscopy, and fluorescence microscopy observing actin and vinculin molecules. The nanopillar structure enabled easy subculture of the cells from the sheets without conventional trypsinization. Moreover, the HeLa cells divided and proliferated on the sheets in a different way to that found on petri dish because of the manner in which the cells adhered to the materials.

Summary form only given. The discrete track and patterned medias are candidates for higher density storage. The principal of read/write abilities has been reported. The production methods for these medias are under investigated. Nanoimprint technology is one of the attractive methods for ultra-fine patterning. The principle of nanoimprint is press molding in nano-scale. There are several points for the industrial applications such as resolution, pattern formation area, precise control of pattern transfer, lifetime of nano-mold, alignment and so on. The resolution of 6 nm half pitch was confirmed using super-lattice nano-mold (M. D. Austin, et al., 2004), and this resolution is good enough for future IT devices. Pattern formation area is also important for device production. The pattern formation on 300 mm diameter wafer was reported (M. Ogino, et al., 2004) by thermal nanoimprint process. Nanoimprint technology is spreading to not only IT/electronic devices but also bio and energy devices. It will be important that choosing the suitable technology for media application among the common nanoimprint technology.

A correlation between the partial pressure of dichlorosilane gas (SiH2Cl2) and the incorporation of oxygen (O) and chlorine (Cl) atoms into the low‐temperature (850 °C) epitaxial films was found. The profiles of O and Cl concentrations in the epitaxial films were measured by secondary ion mass spectroscopy. Incorporation of O and Cl atoms into the growth films during the epitaxial growth was suppressed by increasing the partial pressure of SiH2Cl2. The growth rate linearly increased with the partial pressure of SiH2Cl2 and eventually saturated. Incorporation of O atoms was inhibited and fine removal of Cl atoms was achieved when the growth rates saturated. The epitaxial films with high O and Cl concentrations had a microroughened surface (root mean square of microroughness ≳0.4 nm). The microroughness was also improved by increasing the partial pressure of SiH2Cl2. The coverage of kinks and/or hollow bridge sites by hydrogen (H) and Cl atoms seems to restrict the reaction of O and water (H2O) with the gro...

Nanoimprint technology is new fabrication method to fabricate nano-scale patterns. Fine patterns are formed on a polymer film by pressing a nano-mold that has fine concavity and convexity patterns on the surface. The application fields are spreading to IT-electronics, bio-life science and energy-environmental devices. Principal of nanoimprint and some examples of application will be reported.

Nanoimprint technology is one of the more promising methods for nano-fabrication. The thermal nanoimprint method can fabricate various kinds of thermoplastic materials and its process consists of heating, pressing, cooling, and separation and a lot of research was reported. We proposed and developed a sheet nanoimprint system that enables for continuous treatment of these four basic steps by introducing a belt-shaped nano-mold. We tried to fabricate dot patterns on polymer films by using a sheet nanoimprint method in this work. A 200 nm in diameter and 240 nm tall dots (aspect ratio 1.4) were formed directly onto a 15-m-long polystyrene film. It is important in the field of industrial applications to fabricate nano-scale patterns over a large area with a high throughput. We demonstrated that the sheet nanoimprint is an attractive method for the direct patterning of nano-scale patterns on thermo-plastic films.

We investigated the elongation of polystyrene nanopillars formed by thermal nanoimprint lithography. Silicone and perfluoropolyether were used as mold release agents to obtain molds with different adhesion forces against polystyrene to be imprinted. The adhesion force between the resin and release layers was evaluated as a force curve by atomic force microscope with a polystyrene colloid probe. Elongation depended on the aspect ratio of the corresponding microholes on the mold and the adhesion force against the release layer. The conditions under which the elongation occurred exhibited a clear threshold on the stress loaded on the foot area of the nanopillars.

High-aspect-ratio structures (nanopillars) were used to enhance the fluorescence intensity of immunoassay chips. Nanoimprinting with elongation phenomenon was applied to fabricate polystyrene nanopillars. Human alpha fetoprotein was detected by a fluorescence immunoassay protocol. Fluorescence intensities were evaluated for areas with nanopillars of different surface areas. The area with nanopillars of 95nm diameter and 4.1μm height showed fluorescence intensity 34 times higher than that of flat areas.

The authors found that fine pillar structures (nanopillars) with a high aspect ratio were formed by nanoimprinting with elongation phenomenon. Polymer nanopillars with higher aspect ratios than that of corresponding holes on the mold were obtained without any etching processes after nanoimprinting. The finest nanopillars were 95 nm in diameter and 4.1 μm high made of polystyrene. Elongated nanopillars of poly(methylmethacrylate) and polystyrene were confirmed. Elongation of nanopillars depended on process conditions such as the diameter of holes on the mold, the unmolding temperature, and the molecular weight of the polymer resin.

This is the first report of the successful culturing of HeLa cells on nanopillar sheets–a new type of cell culture dish–in a different way from that on flat petri dishes. Nanopillar sheets were fabricated with a high-aspect ratio structure with a diameter of 80–1000 nm and a height of 1–3 µm using nanoprint technology. Nanopillar structure with 500 nm diameter and 1 µm height enabled easy subculture of the cells from the sheets without the conventional trypsinization method. Moreover, the HeLa cells divided and proliferated on the sheets in the same way as on the flat surfaces with different manner of adhesion.