Deposition of the chemically sensitive polymer layer on SGFET gate by laser-induced chemical-vapour polymerization

The method of laser-induced chemical-vapour polymerization (LID) has been tested to deposit a sensing polymer layer of polypyridine on the gate of a suspended-gate field-effecet transistor (SGFET) gas sensor. Measurements using exposures to organic vapours demonstrate that the SGFET gate located in the narrow (1000 Å) space on the chip can be chemically modified by this alternative method. Compared with currently used electrochemical deposition, the LID method provides very adhesive films with different physicochemical properties, which gives a wider choice of chemically sensing polymer layers available for chemical modification of SGFET sensors.     

Effect of gas pressure on permanent dark image sticking on a bright screen in AC plasma‐display panels

Abstract— The permanent dark‐image‐sticking phenomenon on a bright screen was examined under various gas pressures in a 42‐in. ACPDP with an He(35%)‐Xe(11%)‐Ne gas composition. Infrared‐emission observations reveal that the discharge characteristics related to the MgO surface are almost the same in both the discharge and non‐discharge cells, whereas luminance observations show a deterioration in the visible‐conversion characteristics related to the phosphor layer in both the discharge and non‐discharge cells. Consequently, the permanent dark‐image‐sticking phenomenon on a bright screen is found to be strongly related to the deposition on the phosphor layer to the Mg species sputtered from the MgO surface due to a repetitive strong sustain discharge. For a decrease in gas pressure, the permanent dark image sticking on a bright screen became worse due to a severe degradation of the visible‐conversion characteristics of the phosphor layer caused by the deposition of higher amounts of sputtered Mg species on the phosphor layer, as confirmed by various measurements, such as V_t closed curves, time‐of‐flight secondary‐ion mass spectrometry, photoluminescence, and atomic‐force‐microscope analyses.     

Fabrication of high aspect-ratio polymer microstructures for large-area electronic portal x-ray imagers

Megavoltage X-ray imaging performed during radiotherapy is the method of choice for geometric verification of patient localization and dose delivery. Presently, such imaging is increasingly performed using electronic portal imaging devices (EPIDs) based on indirect detection active matrix flat panel imagers (AMFPIs). These devices use a scintillating phosphor screen in order to convert incident X-rays into optical photons, which are then detected by the underlying active matrix photodiode array. The use of a continuous phosphor introduces a trade-off between X-ray quantum efficiency and spatial resolution, which limits current devices to use only 2% of the incident X-rays. This trade-off can be circumvented by “segmented phosphor screens”, comprising a two-dimensional matrix of optically isolated cell structures filled with scintillating phosphor. In this work we describe the fabrication of mm-thick segmented phosphor screens using the MEMS (micro-electro-mechanical-system) polymer SU-8. This method is capable of being extended to large-area substrates.     

An electrophoretic deposition process for screening phosphor powders for color displays

Abstract— A new process incorporating electrophoretic deposition and a photolithographic technique was developed for coating repeating triads of 75‐μm‐wide stripes composed of green ZnSiO₄:Mn (P1), red Y₂O₃:Eu (P56), and blue ZnS:Ag, Cl (P11) phosphor particles. The resolution of the screens produced is 100 triads of phosphor stripes per inch of substrate. SEM micrographs show a high degree of phosphor stripe edge precision with relatively little cross‐contamination. Cathodoluminescence measurements revealed that the chromaticity of the phosphors were not altered by the coating process.     

LED packaging by ink‐jet microdeposition of high‐viscosity resin and phosphor dispersion

Abstract— An ink‐jet‐printing method applied to the microdeposition of high‐viscosity resin, including optimization of phosphor dispersion for light‐emitting‐diode (LED) packaging was examined for the first time. An ultrasonic ink‐jet‐printing method was used, in which ink droplets are ejected by a focused ultrasonic beam from a nozzle‐less printhead. To fabricate white LEDs, high‐viscosity phosphor‐dispersed resin was deposited to form an encapsulant dome. Two types of methods to control phosphor sedimentation for color uniformity were examined; one is heating the lead frame during the resin deposition, and the other is hydrophobic surface treatment of the lead frame base enabling the fabrication of a small encapsulant dome. For light direction control, a silicone micro lens was deposited on an encapsulant dome using the ink‐jet method. The results show that ultrasonic ink‐jet printing is an applicable technique to optimize and modify on‐demand optical characteristics of LED devices.     

Fabrication of high-aspect-ratio hydrogel microstructures

Microfabrication of high-aspect-ratio polymeric microstructures via deep X-ray lithography traditionally involves either crosslinking or scissioning a polymer film spun-cast on a substrate. A post-exposure development procedure is usually employed to remove the unwanted polymer, leaving behind lithographically patterned structures. Instead, we use a novel synthesis technique wherein polymerization of a mixture of monomers in solvent is initiated, through a mask, with hard X-rays. The resulting polymer precipitates out of the solvent, thus limiting the spatial propagation of the reaction only to the exposed regions. Such a technique offers a unique way for the patterned synthesis of polymers from a variety of monomer-solvent systems. Here, we present the first results on the synthesis of high-aspect-ratio microstructures of a thermoreversible hydrogel, poly (N-isopropylacrylamide), and an ionic hydrogel, poly (methacrylic acid). These stand-alone, implantable microstructures are envisioned to be potentially useful in such diverse areas as biosensors, microactuators, controlled release applications, and cell and tissue engineering.This paper was first presented at the High Aspect Ratio Microstructures (HARMST) 2003 conference in Monterey California, June 2003.We would like to thank Dr. Francesco De Carlo (APS) for his discussions on beamline simulations. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Basic Energy Sciences (BES), Office of Science, under contract number W-31-109-ENG-38.     

LIGA fabrication of nanocrystalline Ni–W alloy micro specimens from ammonia-citrate bath

Ammonia-citrate bath has been investigated for the deposition of nano crystalline Ni–W alloy micro components using the LIGA process. First the bath stability and deposit characteristics were studied. Fabrication of micro specimens were then carried out on silicon substrates covered with novolac as well as thick PMMA resist for LIGA. Effects of different parameters like current density, nickel ion and tungsten ion concentration in the bath, deposition time etc. on the deposit characteristics and current efficiency were studied. The deposited Ni–W samples were characterized by scanning electron microscopy, energy depressive X-ray spectroscopy, light optical microscopy and X-ray diffraction. Results show that during a few tens of hours of deposition, ammonia loss from the covered bath used is minimal and the bath remains stable. Selection of proper bath and deposition parameters allows a window for the deposition of crack free, thick, nano crystalline nickel–tungsten alloys. Using the optimum parameters, it has been possible to fabricate Ni-12 at% W micro tensile specimens with a nominal thickness of 120 μm by the LIGA process.     

Photochromic and irreversible photofluorescent organic materials for 3D bitwise optical memory

This paper presents latest own results in the development of reversible photochromic and irreversible photofluorescent polymer systems providing fabrication of multilayer recording media for 3D optical memory with super high information capacity. It was shown that synthesized thermal irreversible photochromic diarylethenes into plastic binders allow to prepare photochromic polymer layers providing nondestructive refractive read-out of optical information. These photochromic polymer layers were used for preparation of six-layer recording media tested with the positive results using the framed optical device. This device imitated layer-by-layer writing, erasure and read-out of optical signals. Experimental evidences for making photochromic polymer layers based on a mixture of photochromic diarylethene and dye — phosphor with nondestructive fluorescent read-out are presented too. Polymer systems based on light-sensitive chromones manifest an irreversible photochemical transformations of these non-fluorescing compounds into the fluorescent products under UV irradiation. Received results open perspectives for making multilayer optical discs for bitwise working (based on photochromic systems) and archival (based on irreversible photofluorescent systems) optical memory with information capacity more 1 TB.     

温度敏感型高分子膜特性在线测试新方法的研究

温度溶胀性是温度敏感型高分子膜作为智能感应材料的关键特性。研究提出用压电悬臂梁换能器在溶液中在线测试高分子膜的温度溶胀特性。该测试装置由集成压电元件的悬臂梁和高分子膜探针两部分组装而成。高分子膜可以采用不同的化学处理方法固定在探针上。悬臂梁压电元件将高分子膜微小质量的变化转化为压电元件电气阻抗的变化。首先用有限元分析方法和实验方法校准自制压电悬臂梁的频率特性,从理论上得出压电导抗的频率变化与高分子膜质量变化的关系;然后用此装置在溶液中测试了粘贴膜和涂敷膜的温度溶胀特性;结果清晰地表明了高分子膜的低温亲水性和高温疏水性。压电悬臂结构换能器能具有在线正确地测定高分子膜的温度溶胀特性,具有很好的应用前景。     

Adaptive tip-withdrawal control for reliable microfabrication by localized electrodeposition

The electrode tip withdrawal velocity relative to the deposit surface growth rate is found to play a major role in process repeatability, deposit characteristics, and geometry confinement of high aspect ratio microstructures fabricated by localized electrodeposition. The effect of the tip and deposit-surface relative velocities is understood through experimental investigation of deposit characteristics for the three possible cases where the tip withdrawal is; slower than, relatively equal to, and faster than the deposition rate. Best results were obtained when the tip withdrawal is relatively of the same magnitude of the deposition rate. For automation purposes, an adaptive control scheme is proposed to track the deposit surface acceleration, rather than its velocity, by monitoring the tip current gradient, and accordingly withdraw the tip at the same acceleration. This eliminates the need for the intervention of a skilful experimenter, avoids short circuit contact resulting between the tip and deposit surface, and thus greatly improves the repeatability of the process. Critically important to the proposed adaptive tip-withdrawal technique is the initial approach of the tip toward the substrate to assure proper tracking of deposition current. Automation and optimization of the initial tip positioning above the substrate is achieved by tracking deposition current variation with the tip-substrate spacing, thus leading to a better geometry confinement of deposited structures.     

Development and evaluation of piezoelectric-polymer thin film sensors for low concentration detection of volatile organic compounds related to food safety applications

In this study, the regioregular poly (3-hexyl thiophene) (rr-P3HT) based piezoelectric sensors were developed and evaluated to detect alcoholic volatile organic compounds (VOCs) associated with spoiled and Salmonella typhimurium contaminated packaged beef headspace. The drop coating technique was used to deposit thin films of rr-P3HT on both the sides of quartz crystal microbalance (QCM) electrode. The QCM polymer sensors were found to provide repeatable and reproducible sensor response to alcohol VOCs with a fast recovery (<2 min) at room temperature (25 °C). The principal component analysis on the sensors sensitivities was performed to discriminate the sensed alcohol VOCs, namely: 3-methyl-1-butanol from 1-hexanol. The QCM polymer sensors demonstrated selective response to low concentration of 3-methyl-1-butanol (average estimated lowest detection limit (LDL): 4.35 ppm) and to 1-hexanol (average estimated LDL: 3.20 ppm). The 30 days storage study performed on QCM sensors showed identical sensitivity responses for sensing 3-methyl-1-butanol and 1-hexanol at low concentrations.     

Photoresponsive polymer gel microvalves controlled by local light irradiation

This paper presents independent control of multiple microvalves, which are opened by local light irradiation. The application of photoresponsive polymer gel, which was developed by our research group, to photoresponsive microvalve was systematically examined. Photoresponsive polymer gels, which were composed of poly(N-isopropylacrylamide) functionalized with spirobenzopyran chromophore (pSPNIPAAm), were fabricated by in situ photo-polymerization at the desired positions in microchannels. Blue light irradiation to the pSPNIPAAm gels induced shrinkage of the gels and caused the microvalves composed of the gels to open. Local light irradiation to the discrete microvalves enabled independent control of three photoresponsive polymer gel microvalves, which had been fabricated on a single microchip. Each microvalve was opened by 18–30 s light irradiation.     

Efficiency enhancement in blue organic light emitting diodes with a composite hole transport layer based on poly(ethylenedioxythiophene):poly(styrenesulfonate) doped with TiO2 nanoparticles

Blue color organic/polymeric light emitting diodes are very important because they can be used for tri-color display applications, fluorescence imaging, and exciting yellow phosphor for generating white light for general illumination. But the efficiency of blue organic/polymeric light emitting diodes is considerably low due to their large band gap that requires higher energy for effective emission. In this paper we report the enhancement in polyfluorene blue organic light emitting diodes with a polymer nano-composite hole transport layer. Blue light emitting diode based on polyfluorene as an emissive layer and poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate)–titanium dioxide nanocomposite as the hole transport layer were fabricated and studied. Different concentrations of titanium dioxide nanoparticles were doped in poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) in the hole transport layer and the performance of the devices were studied. Significant enhancement in the blue peak at 430 nm of polyfluorene has been observed with increase in concentration of TiO₂ nanoparticles in the hole transport layer. The turn on voltage of the device has also been found to improve significantly with the incorporation of titanium dioxide nanoparticles in the hole transport layer. The optimized concentration of titanium dioxide in the hole transport layer for most efficient device has been found to 15 wt.%.     

Machine vision system for singularity detection in monitoring the long process

We discuss a machine vision system (MVS) for singularity detection when monitoring the long process. The main application of this MVS is the automation of laboratory analysis for determining the number of gel particles in a polymer solution. Components and specifications of the system intended to solve the problem are proposed. As part of the MVS development process, we come forward with novel methods for binary image thresholding and analysis, which prove to be efficient for low contrast images and at fairly high crosstalk levels. The software to realize the aforesaid methods has been developed, allowing the number of gel particles in the polymer solution to be automatically determined. The use of the MVS instead of a human observer enables the psychovisual load on the laboratory staff to be essentially reduced, the accuracy and reliability of determining the number of gel particles in the polymer solution to be enhanced, as well as providing the automatic recording of the laboratory analysis data.     

Self-Oscillating Gel Actuator for Chemical Robotics

In this paper, we introduce self-oscillating gel actuators for chemical robotics. The polymer gels prepared here have cyclic reaction networks like in a metabolic process itself. With a cyclic reaction, the polymer gel swells–shrinks autonomously. The periodic self-oscillating motion of the gel is produced by the dissipating chemical energy of the oscillatory Belouzov–Zhabotinsky reaction. We have succeeded in making the synthetic polymer gel walk autonomously like a living organism. This experimental fact represents the great possibility of the chemical robot.     

Current transport and aging in direct-current powder electroluminescent display devices

Abstract— Direct-current powder electroluminescent (DCPEL) display devices were excited by unipolar voltage pulses, and current flow through the phosphor was recorded. Devices with different formed layer thicknesses were obtained by varying the forming voltage. For a fixed electric field in the formed layer, the phosphor current did not show a substantial increase as the thickness of the formed layer increased. A model is proposed in which tunnel injection from the p-Cu₂S/i-ZnS:Mn interface of a reverse-biased p-Cu₂S/i-ZnS:Mn/n-SnO₂ structure is thought to be the controlling current mechanism. Aging studies revealed that further forming is the dominant degradation mechanism in the early stages, while load-line degradation and softening become the dominant degradation modes as the aging process is continued. The conventional DCPEL device structure was modified by introducing a thin chromium layer just prior to the deposition of the aluminum back electrode. Incorporating chromium reduced the initial series resistance of the device. A hybrid device employing a thin film (1 μm) of ZnS:Mn, sandwiched between two thin dielectric layers (5 nm), was fabricated; ZnS:Mn,Cu powder was sprayed onto the thin-film sandwich. The hybrid structure showed good luminance without forming; however, device degradation with time was still present.     

阻燃型凝胶聚合物电解质在碱金属电池中的研究进展

阻燃型凝胶聚合物电解质不仅具有良好的枝晶抑制作用,还具有不易泄漏、不可燃等高安全特性,可有效解决热失控或机械冲击等造成的安全隐患,在碱金属电池中具有重要应用前景。该文综述了阻燃型凝胶聚合物电解质在碱金属电池(涉及锂、钠、铝、锌等)中的研究进展。该文首先讨论了凝胶聚合物电解质的阻燃机理;其次,总结了阻燃型凝胶聚合物电解质的常用制备方法;再次,论述了不同类别阻燃型凝胶聚合物电解质在不同碱金属电池体系中的应用状况;最后,提出了目前存在的挑战和未来可能的发展方向。     

PAAm􀀁g􀀁CB/Al2O3 凝胶杂合材料的制备及 负蒸气系数效应研究

利用自由基反应机理,以过氧化苯甲酰(BPO)为引发剂,在炭黑表面引入-CH2OH或-C(CH3)2OH;然后再以硝酸铈铵/CB-CH2OH或硝酸铈铵/CB-C(CH3)2OH 组成氧化还原引发体系,在CB表面接枝上聚丙烯酰胺(PAAm-g-CB);在PAAm-g-CB 存在下,进行AIP(异丙醇铝)的溶胶-凝胶化反应,制得了一种新颖的具有智能响应性的PAAm-g-CB/Al2O3凝胶杂合材料.研究了其气敏性能和湿敏性能.结果发现,该杂合材料在其良溶剂蒸气中电阻急剧下降,呈现负蒸气系数现象(NVC);而在不良溶剂蒸气中电阻几乎不发生变化.其响应性能与杂合体间氢键作用密切相关,并受接枝率大小的影响;结合IR、DTA、TGA等分析方法推断了杂合材料分子结构模型.     

Image improvement in a laser projection display with a spatial light modulator with a deformable polymer

Abstract— The image quality of a laser projection display based on a spatial light modulator with a deformable polymer layer (SLMDPL) has been improved. Bias diffraction has been reduced by two methods: (1) by filling the spacings between electrodes with SiO₂ followed by deposition of a slightly conductive thin film and (2) by splitting electrodes. Both methods resulted in a contrast ratio of ?1200:1, which is significantly better than 50:1 measured for an earlier type of SLMDPL. Different methods of reducing the influence of electrical‐charge movement on the image quality have also been investigated. Substantial improvement has been achieved by using an alternating mode for signal voltage pulses, by increasing the conductivity of the gel layer, and by increasing the surface conductivity of the substrate between electrodes. Cross‐talk between neighboring pixels has been suppressed without a loss in the sensitivity by using a special layout of the electrodes in the SLMDPL.     

Applications of OLEDs that use VUV‐CVD films

Abstract— In photo‐CVD (chemical vapor deposition) in which vacuum‐ultraviolet (VUV) excimer lamps (VUV‐CVD) are used, thin films were deposited at room temperature because VUV photons have the energy to decompose material gases. For the use of OMCTS (octamethylcyclotetrasiloxane), an organic siloxane, we can deposit a self‐flatness film for high‐pressure conditions. The reactants generated by VUV photons have excellent migration characteristics for this condition. Also, the VUV‐CVD film demonstrates low stress, comparatively hard hardness, good electrical properties, and good thermal resistance. The VUV‐CVD film is optimum for planarizing film in the over‐coating deposition step in the production of OLEDs, which requires a low‐temperature process.