Laser scanning path generation considering photopolymer solidification in micro-stereolithography

It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010.     

紫外光固化聚合物涂层的原位光稳定化研究

选用实验室制备的四种新型反应型受阻胺类光稳定剂(r-HALS):4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶醇酯(MTMP)、4-丙烯酰氧基-2,2,6,6-四甲基哌啶醇酯(ATMP)、4-甲基丙烯酰氧基-1,2,2,6,6-五甲基哌啶醇酯(MPMP)和4-丙烯酰氧基-1,2,2,6,6-五甲基哌啶醇酯(APMP),实现了紫外光固化聚合物涂层(膜)的原位(in situ)光稳定化。通过室内人工光老化实验和在光氧化过程中黄度指数(Yellowness Index,YI)的监测,再与典型的商用HALS(Tinuvin770和Tinuvin292)进行平行实验对比,考察了r-HALS对紫外光固化聚合物涂层的光防护效果,探索一条紫外光固化聚合物涂层原位(in situ)光稳定化的新途径。     

Portable erythema meter and its application to use in human skin

In this study a compact, hand-held, solid state erythema meter using light emitting diodes is described. This device has been constructed and used to compare with visual assessments of ultraviolet radiation in human subjects. A statistically significant correlation was obtained between erythema index and visual assessment in 24 ultraviolet irradiated subjects. Furthermore, the effects of three aftersun treatments have also been assessed objectively using the meter and subjectively using visual assessments. The ultraviolet-irradiated areas were less red following treatment than the irradiated and untreated areas. The results obtained by the meter were similar to and statistically significant with those obtained by visual assessment.
It is concluded that widespread use of an erythema meter such as that described would greatly improve all cutaneous erythema assessments.     

金属阴极真空型紫外探测器光谱响应测试研究

紫外探测相比红外探测的一个重要优势是背景干净,信噪比高.这一优势充分体现的前提是其日盲特性.本文利用光谱测试系统对制作的金属阴极真空紫外探测器的光谱响应进行测试,并将测试结果与传统的碲铷阴极紫外探测器的光谱响应曲线进行对比,比较了这两类器件的紫外日盲特性,发现金属阴极在日盲特性方面有一定的优势,最终指出该类型器件在某些特殊场合的潜在应用.     

MIS／IL硅太阳电池耐紫外辐射性能的研究

通过比较蒸发铯和浸渍铯在ＭＩＳ／ＩＬ硅太阳电池中所引入的铯量、固定正电荷量、界面态密度和对太阳电池表面面电阻的影响，以及测量上述诸量和太阳电池的主要参数经紫外辐照后的变化，并从表面能带的角度分析了引入铯对太阳电池的紫外辐射稳定性的影响，解释了在ＭＩＳ／ＩＬ硅太阳电池中引入铯使该器件耐紫外辐射性能提高的原因。     

用UV激光加工高密度印制板

在本文中,讨论激光技术的几个基本概念和激光加工材料的机理及其加工实例。     

Ultraviolet detectors based on epitaxial ZnO films grown by MOCVD

High-quality zinc oxide (ZnO) films were epitaxially grown on R-plane sapphire substrates by metalorganic chemical vapor deposition at temperatures in the range of 350°C to 600°C. In-situ nitrogen compensation doping was performed using NH₃. Microstructural and optical properties of the films, as well as the N-doping effects, were studied. The metal-semiconductor-metal ultraviolet sensitive photodetectors were fabricated on N-doped epitaxial ZnO films. The detector showed fast photoresponse, with a rise time of 1 μs and a fall time of 1.5 μs. Low-frequency photoresponsivity, on the order of 400 A/W at 5 V bias, was obtained.     

Physical polymer surface modification methods and applications in food packaging polymers.

Continued innovations in the polymer industry have made polymer surface modification methods a subject of intense research. The importance and necessity of surface modification of plastics are explained, and the advantages of physical surface treatments over the less-sophisticated chemical methods are outlined. Currently available physical surface modification methods for food packaging polymers are reviewed from the food packaging perspective. These physical surface modification methods include flame, corona discharge, UV, gamma-ray, electron beam, ion beam, plasma, and laser treatments. The principle of operation of each method is briefly described, and the advantages and disadvantages of each technique are cited. The extent to which each of these methods can produce the specific modifications desired is discussed. Furthermore, the effects of each treatment on barrier, mechanical, and adhesion properties of food packaging polymers are also examined. Finally, an overview of economic aspects of sophisticated surface modification techniques, including ion beam, plasma, and laser treatments, is presented.     

Effect of pressure on efficiency of UV curing of CVD-derived low-k material at different wavelengths

Low-k dielectrics prepared by CVD in the form of 200 nm thick layers on Si wafers were thermally treated at 410 °C and irradiated using UV lamps emitting photons of different wavelengths around 172 nm, 185 nm, and 222 nm. The treatment was performed in high vacuum and under a nitrogen atmosphere at various pressures ranging from 0.1 mbar up to 700 mbar. Subsequently, the samples were investigated using FTIR transmission spectroscopy, contact angle measurement, X-ray photoelectron spectrometry (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray reflectometry (XRR), surface acoustic wave spectrometry (SAW), and purged UV spectroscopic ellipsometry (PUVSE). It was found that for all UV wavelengths applied for curing the depth profiles of the chemical composition were homogeneous. For all properties evaluated, irradiation at wavelengths below 200 nm resulted in more pronounced changes than at longer wavelengths. Generally, a decrease in residual porogen content, conversion of the Si-O-Si bonds from cage to network/suboxide, degradation of Si-CH₃ bonds, formation of H-SiO bonds, increase in surface energy, changes of element concentrations and of density, increase in Young’s modulus, and changes in dielectric constant were observed. These findings were confirmed by quantum-chemical calculations. With increasing nitrogen pressure the effects were more considerable. An attempt was undertaken to explain the effect of nitrogen pressure in course of the role of nitrogen molecules as collision partners.     

N-channel thin-film transistors constructed on plastic by solution processes of HgSe nanocrystals

We demonstrate bottom-gate thin-film transistors (TFTs) based on solution-processed HgSe nanocrystals (NCs) on plastic substrates. Solid films made of spin-coated HgSe NCs were heated at a temperature of 150 °C for 15 min to maximize the magnitude of their current, and these films were utilized as the channel layers of TFTs. A representative TFT with a bottom-gate Al₂O₃ layer operated as a depletion-mode one with an n-channel, exhibiting a field effect mobility of 3.9 cm²/Vs and an on/off current ratio of about 10². In addition, the electrical characteristics of the TFT on bent substrates are briefly described.