Exposure Step Research Articles

Growing aluminum nitride films by Plasma-Enhanced Atomic Layer Deposition at low temperatures

Aluminum nitride films have been grown by Plasma-Enhanced Atomic Layer Deposition method. It was found that at temperatures of 250 °C and 280 °C increase of the plasma exposure step duration over 6 s, as well as increase of reactor purge step duration over 1 s does not affect the growth rate, however, it affects the microstructure of the films. It was found that crystalline aluminum nitride films deposit with plasma exposure duration over 10 s and the reactor purging over 10 s. When the temperature drops the increase of reactor purge step duration and plasma exposure step duration over 20 s is required for crystalline AlN film growth.

High-Throughput Contact Flow Lithography.

High-throughput fabrication of graphically encoded hydrogel microparticles is achieved by combining flow contact lithography in a multichannel microfluidic device and a high capacity 25 mm LED UV source. Production rates of chemically homogeneous particles are improved by two orders of magnitude. Additionally, the custom-built contact lithography instrument provides an affordable solution for patterning complex microstructures on surfaces.

Multilayer photo-aligned thin-film structure for polarizing photonics.

In this Letter, an advanced multilayer photo-aligned liquid crystal polymer (LCP) thin-film structure with multiple optical functions is introduced. Within each LCP layer, a spatially distribution of local optical axes can be controlled by a patterned photo-alignment layer. As an embodiment of the proposed structure, a two-layer structure with pixelated controlled light-propagation directions and polarizations has been studied, which has shown the potential to be used as a photomask for generating multi-domain photo-alignment structures with a single exposure step. The combination of the multilayer structure with patterned photo-alignment technology provides a new perspective of designing optical structures for polarizing photonics applications.

Low Cost, Low Surface Area Activated Carbon As Anode Material for Neutral pH Aqueous Asymmetric Supercapacitor Applications Via a Simple Surface Modification

Surface modified activated carbon has been developed for use as a low-cost electrode material in aqueous asymmetric electrochemical supercapacitors. Specifically, wood-based activated carbon with a surface area of under 500 m2/g was modified using an intermediate temperature acid exposure step that more than doubled the specific capacitance in a neutral aqueous electrolyte. After the modification step, the carbon was analyzed using x-ray photoelectron spectroscopy, BET, and combustion analysis. The material thus developed gave approximately 200% improvement in the specific capacitance in 1 M Na2SO4; namely 109 F/g when compared against the precursor activated carbon which showed 38 F/g. To prove the possible utility of this material, full asymmetric energy storage cells were made using the modified carbon as the anode active material and Lithium Manganese Oxide as the cathode active material and Na2SO4 aqueous electrolyte. The test cells displayed excellent reversible capacity greater than 40 Ah/kg of activated carbon in anode for over 1000 cycles, which is an effective capacitance of approximately 160 F/g delivered over relatively slow charge/discharge rates. A Simple economic analysis shows that this material is over an order of magnitude more cost effective on a $/Ah basis than off-the-shelf electrochemical double-layer capacitor materials. These encouraging results show great promise in developing low cost energy storage devices while incorporating non-toxic and environmentally benign materials. Figure 1

Analysis of Success and Constraint Factors of Korean Wave Based on Acculturation Model

Korean wave has been developing from a simple concern through the new korean wave era creating economic payoff to the global spread age with the help of social media development. As Korean wave and diverse heterogenous international cultures meet each other during the global spread, we observe phenomena such as selection, adoption, resistance, and reconstitution of culture. However, theoretical system and framework to understand those phenomena and draw policy suggestion for the sustainable expansion of Korean wave is not yet developed. So, this study identifies competitiveness of Korean wave and offers suggestions for sustainable spread of Korean wave by analyzing factors related to friendliness, necessity, imagery during the spread, exposure, selection and adoption step using acculturation model. This study finds that main competitive advantages for Korean wave lie in the standardization of contents production and experience of overseas expansion based on well known famous star. It also finds that the lack of capability for contents generation which can be accepted in the western world beyond Asia is main constraint factor of Korean wave.

在金属基底上制作高深宽比金属微光栅的方法

According to the requirements of optical fields for metal micro devices with higher aspect ratios,a metal micro-grating with the high aspect ratio was fabricated on a metal substrate by using the UV-LIGA technology.The "exposure step by step"and "development once"were used to fabricate a SU-8thick photoresist mold with high aspect ratio to overcome the technologic difficulty in fabrication processing.For the defects of electroforming layer caused by long operation time,the fractional electroforming and other methods were adopted to obtain the electroforming grating structure..At the same time,the line width compensation method was taken to solve the problem that line width of SU-8 photoresist mold was reduced by swelling.In the process of stripping photoresist after electroforming,the ultrasonic method and soaked method were alternately used.Finally,the metal micro-grating with a period of 130μm,and a size of 900μm×65μm×243μm was fabricated.The high aspect ratio of the metal micro-grating reaches 5,and its relative error on overall dimensions is lower than 1%.Moreover,the surface roughness of metal micro-grating is lower than6.17 nm.This research breaks the height limitation and substrate fragile of the exciting fabrication methods for metal micro-gratings with high aspect ratios.

Nanotechnology-based cosmeceuticals.

Cosmeceuticals are the fastest growing segment of the personal care industry, and a number of topical cosmeceutical treatments for conditions such as photoaging, hyperpigmentation, wrinkles, and hair damage have come into widespread use. In the cosmeceutical arena nanotechnology has played an important role. Using new techniques to manipulate matter at an atomic or molecular level, they have been at the root of numerous innovations, opening up new perspectives for the future of cosmeceutical industry. Nanotechnology-based cosmeceuticals offer the advantage of diversity in products, and increased bioavailability of active ingredients and increase the aesthetic appeal of cosmeceutical products with prolonged effects. However increased use of nanotechnology in cosmeceuticals has raised concern about the possible penetration of nanoparticles through the skin and potential hazards to the human health. This review outlines the different nanoparticles used in various classes of cosmeceuticals, nanotechnology-based cosmeceutical products present in the market, and the potential risk caused by nanoparticles on exposure and recent regulatory steps taken to overcome them.

A quantitative risk assessment model for Vibrio parahaemolyticus in raw oysters in Sao Paulo State, Brazil

A risk assessment of Vibrio parahaemolyticus associated with raw oysters produced and consumed in São Paulo State was developed. The model was built according to the United States Food and Drug Administration framework for risk assessment. The outcome of the exposure assessment estimated the prevalence and density of pathogenic V. parahaemolyticus in raw oysters from harvest to consumption. The result of the exposure step was combined with a Beta–Poisson dose–response model to estimate the probability of illness. The model predicted that the average risks per serving of raw oysters were 4.7×10−4, 6.0×10−4, 4.7×10−4 and 3.1×10−4 for spring, summer, fall and winter, respectively. Sensitivity analyses indicated that the most influential variables on the risk of illness were the total density of V. parahaemolyticus at harvest, transport temperature, relative prevalence of pathogenic strains and storage time at retail. Only storage time under refrigeration at retail showed negative correlation with the risk of illness.

Wet Chemical Processing with Megasonics Assist for the Removal of Bumping Process Photomasks

A new generation of negative tone resists by TOK, JSR, and Dow Chemical is gaining momentum in advanced packaging applications. Resist thickness requirements are actually increasing to the 50-100 um range as Cu pillars are adopted to accommodate the tighter pitches required in advanced packaging. In order to form pillars the resist must be thicker to contain the entire bump structure. Thick, negative tone resists are more transparent to exposure light wavelengths than positive tone resists and can be exposed by the lithography process much faster (~1 x 104 cross-linking chemical events are driven by 1 photochemical event vs. 100 – 1000 for positive tone resist).1 Therefore exposure times can be shorter, post-exposure bake steps can be shorter, and delay before or after exposure is not necessary, saving photolithography time and CoO. And, due to more complete cross-linking throughout the resist, the resist mask profiles are truer (from Flack et.al, “A Comparison of New Thick Photoresists for Solder Bumping”, SPIE 2005).1 The major drawback to negative tone resists is that the solvent strip times of the highly cross-linked resist masks are much longer than for positive tone. Flack et.al. noted resist strip times of 5 minutes for two positive resists used in their experiments vs. 50 minutes for the AZ-100nXT negative tone resist, using AZ400T at 80°C (most likely in an immersion tool). Long strip times or special stripping requirements are noted on the data sheets of the other majority suppliers of negative resists as well. Akrion engineers have developed a novel, single-wafer, negative PR strip processes using organic solvents plus Goldfinger megasonics, to provide 30 - 70% reductions in process times and the associated chemical consumption when compared to processes that do not utilize a megasonics assist. The multi-step process can be accomplished in a single process chamber, with each step optimized for time and temperature based on the resist thickness and solvent stripping chemistry used. In the Akrion process, a period of solvent exposure at low wafer spin speed is used initially to begin swelling and dissolving the thick photoresist layer. This is followed by a second solvent exposure step using aggressive frontside megasonic energy to promote polymer chain scission throughout the bulk of the photoresist layer. Following this step A DI water rinse and spin dry step are sufficient to completely remove the solvent, dissolved photoresist and any polymer residues. This paper reviews the development of the Akrion process and several examples of improvement in stripping time and results from work with customers.

High-Throughput Nanofabrication of Infra-red and Chiral Metamaterials using Nanospherical-Lens Lithography

Various infra-red and planar chiral metamaterials were fabricated using the modified Nanospherical-Lens Lithography. By replacing the light source with a hand-held ultraviolet lamp, its asymmetric light emission pattern produces the elliptical-shaped photoresist holes after passing through the spheres. The long axis of the ellipse is parallel to the lamp direction. The fabricated ellipse arrays exhibit localized surface plasmon resonance in mid-infra-red and are ideal platforms for surface enhanced infra-red absorption (SEIRA). We also demonstrate a way to design and fabricate complicated patterns by tuning parameters in each exposure step. This method is both high-throughput and low-cost, which is a powerful tool for future infra-red metamaterials applications.

Interfacial adhesion of photodefinable polyimide films on passivated silicon

Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. Due to the disparity of material properties between the polymer and passivated substrates, interfacial delamination is a reliability concern. Understanding the effects of surface layers and film processing on polyimide adhesion is critical for development of more reliable packages. In this paper, we examine the influence of different cure cycles and UV-exposure on the adhesion between a photodefinable polyimide (HD4100 HD Microsystems) and silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). The tensile strength of the thin film interface is measured by a laser spallation technique. Comparison of interfacial strength associated with cure cycle and UV-exposure indicates increased interfacial strength when films are processed with the exposure step as well as a longer cure cycle. Substrates including an oxygenated passivation layer have improved adhesion over nitride passivation layers. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The interfacial fracture energy for this commercially available photodefinable polyimide on silicon is on the order of 100J/m2. The high toughness of this interface makes it difficult to use more conventional interfacial fracture testing techniques.

Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform

With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability.

035 Novel computer-generated strategies for rapid cryoprotectant loading into mouse and human oocytes

A physics-based mathematical optimization algorithm was used to devise novel strategies for intracellular loading of penetrating cryoprotectants. By coupling computer simulations of mass transport with a cost function that minimizes cryoprotectant exposure time while limiting volumetric excursions, a simplex algorithm was used to optimize two-step cryoprotectant loading procedures for mouse and human oocytes. This resulted in the identification of two new strategies to reduce the time required for cryoprotectant loading, which were then tested experimentally. For example, prior approaches to osmotic manipulation during cryoprotectant loading have been limited to the addition of nonpenetrating excipients (e.g., sugars) that help concentrate intracellular cryoprotectant by drawing out water. In contrast, the optimal computer-generated loading protocol prescribed the use of hypotonic buffers during the initial cryoprotectant exposure step. In particular, to load 1.5 M propane-1,2-diol (PROH) into human metaphase II oocytes at room temperature, the optimization algorithm predicted that oocytes should initially be exposed for 5.5 min to a solution containing 1.3 M of the cryoprotectant and 50 mOsmol/L saline, following which oocytes are predicted to reach equilibrium with only 0.5 min additional exposure to the final 1.5 M PROH solution (in isotonic buffer). This protocol results in less than half the 15 min cryoprotectant exposure time required to load the same amount of PROH using a conventional one-step addition method, while also reducing the magnitude of deleterious volume excursions. A second strategy suggested by computer simulations was to perform cryoprotectant loading at elevated temperatures, to increase the rate of molecular transport. Higher temperatures are typically assumed to result in increased cytotoxicity, to wit, the fertilization rate of mouse oocytes after one-step loading 1.5 M Me 2 SO at 30 °C (8%) was found to be much lower than the fertilization rate for one-step loading at room temperature (34%). However, this assumption has not previously been tested using experimental protocols based on optimal cryoprotectant exposure times. When using a mathematically optimized two-step loading protocol, fertilizability of mouse oocytes after Me 2 SO addition at 30 °C was 86%, comparable to that of controls (96%). Combining the temperature elevation technique with the hypotonic diluent strategy, an optimized protocol (2.4 min exposure to 1.4 M Me 2 SO in 50 mOsmol/L phosphate-buffered saline, followed by an 8-s exposure to isotonic saline with 1.5 M Me 2 SO) resulted in fertilization and blastocyst formation rates of 92% and 88%, respectively, comparable to those of controls. Applying the same approaches to the development of methods for loading human oocytes with penetrating cryoprotectant, the computer algorithm generated an optimal two-step protocol that is predicted to require only 83 seconds to load 1.5 M PROH. The optimal protocol consists of an initial 79-s exposure at 30 °C to a solution containing 1.4 M PROH and 50 mOsm salt, followed by a 4-s equilibration in the 1.5-M cryoprotectant solution. Source of funding: National Institute of Child Health and Human Development Grant No. R01HD049537, awarded to AE. Conflict of interest: None declared. jens.karlsson@villanova.edu

Facile fabrication of high-resolution extreme ultraviolet interference lithography grating masks using footing strategy during electron beam writing

The authors demonstrate a method for facile fabrication of transmission grating masks used in extreme ultraviolet interference lithography (EUV-IL) based on a footing strategy during electron beam writing of mask gratings. By modifying the electron beam lithography pattern and dose distribution, a thin footing is generated between the mask grating lines. This thin footing layer effectively prohibits subsequent metal deposition using a standard electroplating setup in the grating region, while outside the grating region metal is electrodeposited freely, absorbing EUV radiation and serving as an EUV-IL mask grating central photon stop layer. The strategy the authors present greatly simplifies the mask fabrication process and increases the yield, as the crucial central stop region can be fabricated directly and without further overlay exposure steps either using electron beam or photolithography.

Photo‐Activatable Surfaces for Cell Migration Assays

AbstractA simple material platform for advanced cell migration studies is presented. It relies on surfaces modified with photo‐activatable adhesion peptides and two light exposure steps to independently trigger attachment and migration. The light‐controlled exposure of adhesive ligands allows precise and selective control over integrin‐mediated adhesion and migration events, including their dynamic variation. By using a microscope‐coupled scanning laser, user‐defined geometry, size and composition of the adhesion and migration spaces are possible and simply defined by the laser scanning parameters. Time lapse and high resolution microscopy are possible during the complete process. The miniaturization capabilities of this assay also allow (i) parallel or sequential migration experiments and controls on the same view field of the microscope, (ii) migration studies in confined and unconventional geometries or (iii) activation of migration spaces at subcellular resolution, all of these with minimum material and time consumption. The photo‐activatable surfaces will allow studies of the dynamics of integrin‐dependent migration processes with unprecedented flexibility, multiplexing, reproducibility, and spatiotemporal resolution.

G153 Determinants of Quality of Life in Children with Asthma Who Live in Scotland

BackgroundChildhood asthma is a common chronic condition which may be associated with reduced quality of life (QoL). Factors which determine QoL are important to child, parent and clinician and, in...

Re-Isolating Batrachochytrium dendrobatidis from an Amphibian Host Increases Pathogenicity in a Subsequent Exposure

Controlled exposure experiments can be very informative, however, they are based on the assumption that pathogens maintained on artificial media under long-term storage retain the infective and pathogenic properties of the reproducing pathogen as it occurs in a host. We observed that JEL284, an in vitro cultured and maintained isolate of Batrachochytrium dendrobatidis (Bd), was becoming less infectious with successive uses. We hypothesized that passing an isolate propagated on artificial media through an amphibian host would make the isolate more infectious and pathogenic in subsequent exposures. To test our hypothesis, we used two discreet steps, a reisolation step (step 1) and a comparative exposure step (step 2). In step 1, we exposed eastern spadefoot toads, Scaphiopus holbrooki, to JEL284 and JEL197, another isolate that had been maintained in vitro for over six years. We then re-isolated JEL284 only from a successful infection and named this new isolate JEL284FMBa. JEL197 did not infect any amphibians and, thus, did not proceed to step 2. In step 2, we compared infectivity and pathogenicity (mortality and survival time) of JEL284 and JEL284FMBa by exposing 54 naïve S. holbrooki to three treatments (JEL284, JEL284FMBa, and negative control) with 18 individuals per group. We found that JEL284FMBa caused higher mortality and decreased survival time in infected individuals when compared to JEL284 and negative controls. Thus, our data show that pathogenicity of Bd can decrease when cultured successively in media only and can be partially restored by passage through an amphibian host. Therefore, we have demonstrated that pathogenicity shifts can occur rapidly in this pathogen. Given the potential for shifts in pathogenicity demonstrated here, we suspect Bd to have similar potential in natural populations. We suggest that, when possible, the use of freshly isolated or cryopreserved Bd would improve the quality of controlled exposure experiments using this pathogen.

Lower intracellular concentration of cryoprotectants after vitrification than after slow freezing despite exposure to higher concentration of cryoprotectant solutions

What is the intracellular concentration of cryoprotectant (ICCP) in mouse zygotes during vitrification (VIT) and slow-freezing (SLF) cryopreservation procedures? Contrary to common beliefs, it was observed that the ICCP in vitrified zygotes is lower than after SLF, although the solutions used in VIT contain higher concentrations of cryoprotectants (CPs). To reduce the likelihood of intracellular ice crystal formation, which has detrimental effects on cell organelles and membranes, VIT was introduced as an alternative to SLF to cryopreserve embryos and gametes. Combined with high cooling and warming rates, the use of high concentrations of CPs favours an intracellular environment that supports and maintains the transition from a liquid to a solid glass-like state devoid of crystals. Although the up-to-date publications are reassuring in terms of obstetric and perinatal outcomes after VIT, a fear about exposing gametes and embryos to high amounts of CPs that exceed 3-4-fold those found in SLF was central to a debate initiated by advocates of SLF procedures. Two experimental set-ups were applied. The objective of a first study was to determine the ICCP at the end of the exposure steps to the CP solutions with our VIT protocol (n = 31). The goal of the second investigation was to compare the ICCP between VIT (n = 30) and SLF (n = 30). All experiments were performed in triplicates using mouse zygotes. The study took place at the GIGA-Research Institute of the University of Liège. Cell volume is modified by changes in extracellular osmolarity. Hence, we estimated the final ICCP after the incubation steps in the VIT solutions by exposing the cells to sucrose (SUC) solutions with defined molarities. The ICCP was calculated from the SUC concentration that produced no change in cell volume, i.e. when intra- and extracellular osmolarities were equivalent. Cell volume was monitored by microscopic cinematography. ICCP was compared between SLF and VIT based on the principle that a high ICCP lowers the probability of (re)crystallization during warming but increases the probability of over-swelling of the cell due to fast inflow of water. The survival rates of mouse zygotes after SLF or VIT were compared using either (i) various warming rates or (ii) various concentrations of SUC in the warming dilution medium. The ICCP in mouse zygotes during the VIT procedure prior to plunging them in liquid nitrogen was ∼2.14 M, i.e. one-third of the concentration in the VIT solution. After SLF, the warming rate did not affect the zygote survival rate. In contrast, only 3/30 vitrified zygotes survived when warmed slowly but as many as 30/30 zygotes survived when warming was fast (>20 000°C/min). Vitrified zygotes showed significantly higher survival rates than slow-frozen zygotes when they were placed directly in the culture medium or in solutions containing low concentrations of SUC (P < 0.01). These two experiments demonstrate a lower ICCP after VIT than after SLF. The results should not be directly extrapolated to other stages of development or to other species due to possible differences in membrane permeability to water and CPs. The low ICCP we observed after VIT removes the concern about high ICCP after VIT, at least in murine zygotes and helps to explain the observed efficiency and lack of toxicity of VIT. The study was funded by the FNRS (National Funds for Scientific Research). The authors declare that they have no competing interests.

The stress response resolution assay. I. Quantitative assessment of environmental agent/condition effects on cellular stress resolution outcomes in epithelium

The events or factors that lead from normal cell function to conditions and diseases such as aging or cancer reflect complex interactions between cells and their environment. Cellular stress responses, a group of processes involved in homeostasis and adaptation to environmental change, contribute to cell survival under stress and can be resolved with damage avoidance or damage tolerance outcomes. To investigate the impact of environmental agents/conditions upon cellular stress response outcomes in epithelium, a novel quantitative assay, the "stress response resolution" (SRR) assay, was developed. The SRR assay consists of pretreatment with a test agent or vehicle followed later by a calibrated stress conditions exposure step (here, using 6-thioguanine). Pilot studies conducted with a spontaneously-immortalized murine mammary epithelial cell line pretreated with vehicle or 20 µg N-ethyl-N-nitrososurea/ml medium for 1 hr, or two hTERT-immortalized human bronchial epithelial cell lines pretreated with vehicle or 100 µM zidovudine/lamivudine for 12 days, found minimal alterations in cell morphology, survival, or cell function through 2 weeks post-exposure. However, when these pretreatments were followed 2 weeks later by exposure to calibrated stress conditions of limited duration (for 4 days), significant alterations in stress resolution were observed in pretreated cells compared with vehicle-treated control cells, with decreased damage avoidance survival outcomes in all cell lines and increased damage tolerance outcomes in two of three cell lines. These pilot study results suggest that sub-cytotoxic pretreatments with chemical mutagens have long-term adverse impact upon the ability of cells to resolve subsequent exposure to environmental stressors.

Optical compensator with switchable modes using polymer stabilized liquid crystals

We propose an optical compensator configuration with switchable modes by combining the polymer stabilized liquid crystal (PSLC) technology with the novel electrode design. It could be applied to a fixed-focus lens module for providing the defocus compensation of an optical imaging system. The device has two operation modes that can be switched by the electrode connection and provide respective optical retardation effects. It was designed by using the optical simulation tool and fabricated by using the standard photolithographic processes, the liquid crystal (LC) cell assembly procedure, and the particular ultra-violet (UV) exposure steps. The device was implemented and experimental results qualitatively showed its feasibility for realizing the capability of switching different compensation modes.