HEC/PVDF作为光纤湿度传感器感湿材料性能研究

制作了一种基于以聚偏氟乙烯(PVDF)/羟乙基纤维素(HEC)共混物为感湿材料的折光率变化型光纤湿度传感器.对共混物感湿膜的膜厚度、皮层长度以及共混物的配比进行了考察,并用扫描电镜(SEM)对感湿膜进行了表征.结果表明:用PVDF和HEC共混物合成的感湿膜具有抗人为涂层误差、常温下无需温度补偿等优点;材料PVDF:HEC为1:2制备的感湿膜性能最优,具有宽检测范围和高灵敏度.     

光强调制型光纤湿度传感器评述

综述了湿度传感器的发展概况;重点分析和介绍了吸收型、折光率变化型及光散射型三类光强调制型光纤湿度传感器的感湿机理与研究成果;展望并讨论了光强调制型光纤湿度传感器的发展趋势和应用前景。     

用复阻抗法分析纳米钛酸钡湿敏元件感湿机理

用复阻抗方法对硅衬底纳米钛酸钡湿敏元件的感湿机理进行了分析。实验测量了湿敏元件在不同相对湿度下的复阻抗特性曲线及阻抗、电容等参数随频率的变化曲线。分析出相应的等效电路,推导了等效电路有关参数,分析讨论了纳米钛酸钡湿敏元件的感湿机理。低湿时,感湿材料本身颗粒电阻和电容及吸附的少量水分子共同起作用;高湿时,吸附的水分子电离和极化起主要作用。     

PI电容湿度传感器结构改进与性能分析

本文分析了电容型湿度传感器的电极和感湿膜的几何形状,设置感湿膜单元结构为圆柱体或者瓶径体等形状,增大接触面积以减少响应时间,整体感湿膜单元排列成圆环形阵列,上电极也采用圆环形阵列排列,覆盖在感湿单元阵列上方.最后对设计的传感器灵敏度,响应时间等性能进行了分析,得出了有益的结论.     

PI电容温度传感器结构改进与性能分析

本文分析了电容型湿度传感器的电极和感湿膜的几何形状,设置感湿膜单元结构为圆柱体或者瓶径体等形状,增大接触面积以减少响应时间,整体感湿膜单元排列成圆环形阵列,上电极也采用圆环形阵列排列,覆盖在感湿单元阵列上方。最后对设计的传感器灵敏度,响应时间等性能进行了分析,得出了有益的结论。     

高分子湿敏材料功能设计

本文介绍了高分子湿敏材料的特点,分类,并从敏感材料功能设计的基点出发,较详细地叙述了胀缩型、电阻型、电容型高分子湿敏材料的感湿机理和感湿材料设计方法,同时以应用示例给予说明。     

聚酰亚胺的感湿活性中心

通过酰亚胺化温度和时间对元件性能影响的试验，研究聚酰亚胺感湿膜的感湿机理。提出了感湿膜中存在着活性中心羰基－ＣＯＯＨ及活性中心－ＣＯＯＨ在酰亚胺化过程中的变化。这种活性中心即是感湿的因素，也是不稳定的原因。若制备性能优越怕元件，需使元件具有稳定的感湿活性中心，要对聚酰亚胺改性，使其具有新的稳定的活性中心。     

MgCr_2O_4-TiO_2系湿敏机理的探讨

半导瓷湿度传感器已经得到了广泛的应用,但是关于感湿机理的探讨尚未解决。本文对MgCr_2~-O_4~--TiO_2~-系湿敏陶瓷的感湿机理进行了详细的研究。根据一系列实验事实,提出了电子-离子共同导电的湿敏机理,该机理能够完善地解释湿敏特性。     

新型陶瓷湿敏元件的性能研究

本文介绍了用金属氧化物陶恣材料制成的湿敏元件及其感湿特性，对陶恣材料的结构以及元件的感湿特性与陶材料结构的关系进行了初步的探讨。     

多孔Al_2O_3薄膜感湿材料的湿敏特性研究

通过对阳极氧化多孔Al2 O3 薄膜感湿材料的制备工艺及其电容湿敏特性进行研究 ,将阳极氧化参数对多孔Al2 O3 薄膜的结构和形态的影响与多孔Al2 O3 薄膜作为湿度传感器感湿材料的湿敏特性联系起来进行分析 ,为优化制备工艺参数提供更充分的实验数据 ,使新型多孔Al2 O3 薄膜湿度传感器具有更好的感湿特性。     

多波长边缘电场传感器参数估计算法的研究

多波长边缘电场传感器由于具有单边穿透、多种穿透深度及层析成像等优点,广泛用于工业过程控制中被测多层样本特性的无损测量.如何建立传感器的输出与多层特性之间的关系一直是参数估计算法的研究难点.以三波长交叉指型边缘电场传感器为例,基于三维有限元仿真,建立了多层样本介电特性和互导电容之间的多元非线性回归模型,研究参数估计算法,实验结果表明算法的有效性.     

A traction-free-edge hybrid-stress element for the analysis of edge effects in cross-ply laminates

A hybrid-stress formulation is presented for the analysis of multilayer cross-ply laminates under uniform inplane strain and a special-purpose element is developed for which the traction-free edge conditions are exactly satisfied. Results obtained for interlaminar stress distributions are shown to converge to large, but finite, values near the free edge. The importance of exact representation of the traction-free edge conditions is examined by comparison of results with those obtained by other investigators and by using an analogous multilayer hybrid-stress element in which the free-edge conditions are approximately satisfied. It is concluded that exact representation of the free-edge conditions is required if accurate point-by-point stress distribution in the vicinity of the free-edge are essential, as in the study of laminate strength and failure.     

An amperometric glucose biosensor based on layer-by-layer GOx-SWCNT conjugate/redox polymer multilayer on a screen-printed carbon electrode

An amperometric glucose biosensor based on a multilayer made by layer-by-layer assembly of single-walled carbon nanotubes modified with glucose oxidase (GOx-SWCNT conjugates) and redox polymer (PVI-Os) on a screen-printed carbon electrode (SPCE) surface was developed. The SPCE surface was functionalized with a cationic polymer by electrodeposition of the PVI-Os, followed by alternating immersions in anionic GOx-SWCNT conjugate solutions and cationic PVI-O solutions. The purpose is to build a multilayer structure which is further stabilized through the electrodeposition of PVI-Os on the multilayer film. The electrochemistry of the layer-by-layer assembly of the GOx-SWCNT conjugate/PVI-Os bilayer was followed by cyclic voltammetry. The resultant glucose biosensor provided stable and reproducible electrocatalytic responses to glucose, and the electrocatalytic current for glucose oxidation was enhanced with an increase in the number of bilayers. The glucose biosensor displayed a wide linear range from 0.5 to 8.0 mM, a high sensitivity of 32 μA mM⁻¹ cm⁻², and a response time of less than 5 s. The glucose biosensor proved to be promising amperometric detectors for the flow injection analysis of glucose.     

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.     

Plane strain sliding contact of multilayer magnetic storage thin-films using the finite element method

The sliding contact or scratch behavior of multi-layer thin-films such as those found in magnetic storage disks has been studied using the finite element method. A rigid cylinder sliding over a multilayered thin-film half-space was implemented to simulate the contact between a feature of the recording slider (such as the protrusion on the trailing edge of the slider, which is part of the thermal flying-height control, TFC) and the magnetic storage multilayer disk. The effects of different parameters such as normal load, friction coefficient and TFC radius on the von Mises, shear and principal stresses in the multilayer system were analyzed. Results showed that under sliding conditions, for a given normal load, the friction coefficient influences the location and magnitude of the plastic strain in the multilayer system. Repeated sliding contact was also performed to characterize its effect on the stress and strain behavior under various loading conditions and investigate shakedown behavior.     

Multilayer patterning technique for micro- and nanofluidic chip fabrication

Polymer micro- and nanofluidic chips become increasingly significant for medical and biological applications. However, it is difficult to fabricate micro- and nanochannels integrately into a polymer substrate due to the reflow and insufficient flow of the polymer. In the present paper, micro- and nanochannels were hot embossed into a multilayer substrate by micromold and nanomold, respectively. To replicate high replication precision nanochannels without damaging the fabricated microchannels, the embossing parameters were optimized by Taguchi and analytic hierarchy process methods. The fabricated micro- and nanochannels were fully sealed at bonding parameters optimized according to the bonding rate of the chip. The fluorescence image indicates that there is no blocking or leakage over the entire micro- and nanochannels. With presented fabrication method, low-cost polymer micro- and nanostructures can be fabricated, which allows for commercial manufacturing of micro- and nanofluidic chips.     

Development of an integrated CMOS DNA detection biochip

This paper presents a CMOS DNA detection biochip using an electrical detection method with self-assembly multilayer gold nanoparticles (AuNPs). Each measuring spot of this biochip consists of three major parts; a pair of electrodes with a nanogap, a current amplifier circuit, and a heater with an embedded temperature sensor. The biochip is first fabricated by a TSMC (Taiwan Semiconductor Manufacturing Company Ltd.) 0.35 μm 2P4M standard CMOS process. Then, post-CMOS micromachining etch processes are used to expose the surface of the nanogap to test samples for the establishment of multilayer AuNPs through hybridization between single strand DNAs in the samples. The gap distance between a pair of electrodes is 350 nm. Before taking DNA detection measurements, self-assembly monolayer AuNPs is established on the nanogap surface between two microelectrodes. Multilayer AuNPs can be observed if hybridization between single strand DNAs occurs. An approximately 1000-fold increase in electric current between the multilayer AuNPs over the monolayer AuNPs serves an indication of the presence of target DNA in test samples. After integrating the electrodes with an embedded current amplifier, the electric current of multilayer AuNPs is amplified to the order of mA that can be easily measured by a commercial Volt-Ohm-Milliammeter. The heating system with a heating element and a temperature sensor can be used to distinguish single base-pair mismatch hybridization from complementary hybridization for the establishment of multilayer AuNPs. The lowest detectable concentration of target DNA on this biochip is 0.1 nM.     

A finite element model for the analysis of viscoelastic sandwich structures

In this work a finite element model is developed for vibration analysis of active–passive damped multilayer sandwich plates, with a viscoelastic core sandwiched between elastic layers, including piezoelectric layers. The elastic layers are modelled using the classic plate theory and the core is modelled using the Reissener–Mindlin theory. The finite element is obtained by assembly of N “elements” through the thickness, using specific assumptions on the displacement continuity at the interfaces between layers. The lack of finite element plate-shell models to analyse structures with passive and active damping, is the principal motivation for the present development, where the solution of some illustrative examples and the results are presented and discussed.     

Modeling of single and multilayer polyvinylidene fluoride film for micro pump actuation

Micro pumps are essential components of micro devices such as drug delivery systems. Large numbers of pumps have been proposed based on different actuating principles. Piezoelectric actuation offers advantages such as reliability and energy efficiency. Lead zirconate titanate (PZT) based piezoelectric actuation for micro pumps is predominantly explored despite its disadvantages such as brittle nature, low straining and difficulties in processing. Polymer piezoelectric materials like polyvinylidene fluoride (PVDF) could be promising replacements for PZT owing to their availability in form of films and good strain coefficients. Very limited literature on micro pump with PVDF as an actuator is available. In this paper, finite element analysis (FEA) model of a micro pump actuator using single and multilayer PVDF for actuation is developed in ANSYS^?. The model takes into account the influence of driving voltage and actuator geometry. The central deflection of the pump diaphragm which is instrumental in defining the pump performance is studied for driving voltages of 100?C200?V. The deflection of the pump diaphragm for single layer and multilayer actuation are determined from the model. It could be inferred from the initial part of the study that pump performance depends on driving voltage and actuator film thickness. In order to reduce driving voltage requirement multilayer stacked actuator is tried with four different configurations of the layers. It is concluded that stacking configuration of parallel energized straight polarity PVDF layers yielded best central deflection. An attempt is made to compare the performance of multilayer actuator with an equivalent single thick layer actuator. It is noticed that the multilayer actuator performance was better by about 101% when number of layers is doubled.     

Numerical and experimental studies by BEM and FEM for multilayer nonhomogeneous structural elements

In civil buildings, walls must satisfy conditions concerning strenght and thermic regime simultaneously. Special attention must be paid to the contact between the layers. The paper studies these problems for a particular structural element built by a multilayer composite. In order to determine the stresses and the displacements in the layers FEM is used whereas the stress concentration is obtained by BEM.