表面镀金SU-8微柱的低频电动旋转特征

依据传统Maxwell-Wagner界面极化理论, 金属微纳米粒子由于具有极高电导率, 在旋转电场作用下无明显电旋转运动. 然而, 本文针对镀金SU-8微柱开展实验研究, 发现镀金微柱在低频条件下的快速旋转运动现象. 据此, 通过考虑镀金微柱表面双电层效应, 理论分析并实验验证镀金微柱的低频电旋转特征. 首先, 建立电场中微柱的近似椭球模型, 分析固-液接触面双电层作用下的金属粒子极化机理, 推导旋转电场作用下镀金微柱的转矩公式及电旋转角速度公式. 其次, 搭建实验平台, 分别对镀金微柱在三种不同电导率溶液、100 Hz–30 MHz频率范围内的电旋转特征进行对比实验研究. 最后, 对实验结果进行分析和讨论, 并通过考虑镀金微柱与基底之间摩擦作用等因素, 验证实验研究与理论研究的一致性. 关键词： 表面镀金微柱 电旋转 双电层 微流控     

低压双液体变焦透镜的理论及工艺研究

通过对仅有单层介电薄膜双液体变焦透镜模型的相关理论分析,得出介电层薄膜的厚度及均匀性对双液体变焦透镜的性能影响很大,并绘制了双液体变焦透镜焦距与驱动电压、介电层厚度的关系曲线.在此基础上,以降低双液体变焦透镜的驱动电压为目的,对介电层的选择进行了分析,选择既可充当介电层又可充当疏水层的派瑞林材料作为双液体变焦透镜的介电层材料,通过真空蒸发镀膜工艺得到了合适厚度的介电层派瑞林薄膜,并对所镀薄膜表面形貌以及厚度进行了测试.选择氯化钾以及溴代十二烷作为导电液体和油性液体,利用离心方式除去液体中溶有的气体,进而制作完成双液体变焦透镜样品.电驱变焦实验得到低压双液体变焦透镜样品的变焦范围为±20mm,驱动电压约为30V,对于实验过程中出现的迟滞效应,通过对杨氏方程中引入摩擦力项,合理地解释了其原因.     

多能场复合电沉积对Al2O3-Co复合薄膜物性影响研究

采用多能场复合微细电沉积加工技术,制备了微观结构渐变的多彩结构色磁性Al₂O₃-Co复合薄膜.在沉积电场和与之垂直的偏转电场作用下,复合薄膜的微观结构、光学特性和磁性沿偏转电场方向呈现渐变特征.通过建立微观结构等效模型,理论分析了复合薄膜微观结构变化机理.通过软件仿真定量分析了沿偏转电场方向Co离子沉积电流密度分布规律,仿真结果与理论研究和实验结果相吻合.研究发现,采用多能场复合的微细电沉积加工技术可以从微观角度调控复合薄膜微区结构,实现对薄膜微区磁学和光学特性的精细调控.     

电润湿液滴微流控芯片液滴驱动的EHD数值模拟

利用液滴电水动力学方法,通过求解耦合的N-S方程,VOF方程以及电场方程,首次对电润湿非接地型单板式(开放式)液滴微流控芯片的液滴驱动过程进行了数值模拟研究.结果表明,在液滴向驱动电极运动的过程中,液滴形态呈现摇摆特性,前进和后退接触角呈现震荡特性,液滴运动速度逐渐下降,并最终停留在零电极和驱动电极的中间位置.     

电液动力微泵的改进

介绍了微型电液动力泵的优化设计和工艺改进。电液动力微泵制作工艺的改进包括:材料的选择,微电极的优化设计和封装工艺的改进。使用聚二甲基硅氧烷(PDMS)作为构建微流道的材料,采用浇注法制作了PDMS微流道,并采用阳极键合方式进行微泵的封装。使用无水乙醇为工作流体对微泵进行流动实验,在驱动电压为90 V时,电液动力微泵驱动流体的最大流速可以达到92 uL/min。     

相移干涉法测量ICF微球内表面粗糙度

 通过分析光线通过微球壳层后各界面的相位分布,讨论了相移干涉法测量微球内表面粗糙度的基本原理,研究了微球上部壳层对内表面粗糙度测量的影响,得到了聚苯乙烯,聚a甲基苯乙烯微球的内表面形貌特征图像,测量数据与原子力显微镜测量数据在同一量级。以微球壳层对超光滑碳化硅及单晶硅片表面形貌的调制作用为研究对象,讨论了微球的外表面粗糙度以及微球壁厚对内表面粗糙度测量结果的影响,确定了相移干涉法测量微球内表面粗糙度的不确定度,实验结果表明：对于表面粗糙度小于30 nm、厚度小于9 mm的微球,测量不确定度小于0.4 nm。     

低压驱动高阻值层液晶透镜

针对传统电极驱动液晶透镜的电场分布在驱动电极边缘的问题,设计了一种高阻值层驱动电极来控制液晶分子偏转的低压驱动和焦距可调的液晶透镜.利用磁控溅射工艺在含镂空孔阵列的面状铝电极基板表面沉积一层掺铝氧化锌透明薄膜,形成高阻值层驱动电极;利用液晶盒成盒工艺将制备好的驱动电极基板和公共电极基板(氧化铟锡玻璃基板)组装成液晶透镜,研究掺铝氧化锌高阻值层、驱动电压、工作频率对液晶透镜光学性能的影响.实验结果表明,对比传统电极驱动液晶透镜,高阻值层电极驱动液晶透镜在驱动电压2.2Vrms和工作频率130kHz下获得的干涉圆环均匀,聚焦光斑小.同时,在驱动电压1.8～2.8Vrms和工作频率130kHz下所制备的液晶透镜焦距可调范围为4.27～2.88mm.     

双辉光放电静电场数值模拟及场分布边角效应分析

根据双辉光放电3个电极极板上的电势,利用边界元积分方程建立以面电荷密度为未知量的离散方程,通过求解线性方程组计算3个电极极板上面电荷的不均匀分布.由极板上的不均匀面电荷分布计算在真空状态下空间任意一点的电势和电场的空间分布,利用数值解对真空状态下双辉光离子渗金属实验装置场分布边角效应进行了分析.     

快前沿直线脉冲变压器多间隙气体开关直流自击穿特性

针对一种用于快前沿直线脉冲变压器(FLTD)的堆栈式多间隙气体开关,研究了电极表面粗糙度、电场不均匀系数、放电电流、气体压强等因素对开关自击穿电压分散性的影响.电极表面粗糙度0.1-0.8μm时,击穿电压平均值没有明显变化,击穿电压分散性小于1.5%;电场不均匀系数为1.20和1.30时,电极烧蚀均匀,开关自击穿电压分...     

常压下气体放电等离子体振荡的实验与理论研究

在实验上研究了高压交流电弧发生器电极间隙的气体放电及等离子体振荡, 观察到了气体放电过程中的纳秒脉冲.以电子的流体运动方程和麦克斯韦方程为理论基础, 利用δ函数来描述交变外电场作用下电极处的电子堆积现象,建立了常压下气体放电时等离子体在外电场中振荡的理论模型,通过Laplace变换求解出电极间的放电电压.理论与实验结果基本符合, 从而可估算出实验中等离子体的电子数密度为1.3× 10¹²/m³.     

Development of mean-field electrical double layer theory

In order to understand the electric interfacial behavior, mean field based electric double layer(EDL) theory has been continuously developed over the past 150 years. In this article, we briefly review the development of the EDL model, from the dimensionless Gouy–Chapman model to the symmetric Bikerman–Freise model, and finally toward size-asymmetric mean field theory models. We provide the general derivations within the framework of Helmholtz free energy of the lattice–gas model, and it can be seen that the above-mentioned models are consistent in the sense that the interconversion among them can be achieved by reducing the basic assumptions.     

A numerical model of streamlines in coplanar electrodes induced by non-uniform electric field

A new model for investigating the non-uniform electric field and potential distribution of fluid flow and streamlines induced by non-uniform electric field with the induced charge in the electrical double layer on the electrode surfaces is presented. Accurate computation of the non-uniform electric field is a pre-requisite for observing fluid flow and streamlines. The electric field distribution is obtained from Laplace's and Neumann's equations. Finite Element Methods is adopted for this work. The simulation results has been compared with available experimental observations of the fluid flow profile obtained by superimposing images of particle movement in a plane normal to the electrode surface. A good agreement is found between the numerical and experimental streamlines.     

A multi-fluid stagnation-flow plasma model with self-consistenttreatment of the collisional sheath

A two-temperature, multifluid model of a plasma in stagnation flow against a cooled, electrically biased surface is presented. The model couples bulk fluid motion, species diffusion and convection, electron and bulk energy equations, and net finite-rate ionization with Poisson's equation for the electric field in a generalized formulation. Application of the model to argon flow reveals important interactions between thermal, hydrodynamic, chemical and electrical boundary layers, with implications for current-limiting regimes of arcjet operation. The response of a planar Langmuir probe in contact with a collisional, flowing plasma is examined. Determinations of current-voltage behavior compare well with simple theory, including dependence on incident plasma velocity. Departures from this theory arise from boundary-layer perturbations near the electrode surface, away from free-stream conditions. The computational model incorporates a finite-rate catalytic recombination of ions and electrons at the electrode surface together with a specified current     

Side-chain effects on the capacitive behaviour of ionic liquids in microporous electrodes

Classical density functional theory (cDFT) is used to investigate electrosorption of ionic liquids in porous electrodes within the framework of a coarse-grained model. The purpose of this study is to clarify the influence of the side alkyl chains of imidazolium cations on the electric double layer (EDL) capacitance that was studied in a number of recent investigations but with contradictory trends. For an ionic liquid near a planar electrode, cDFT predicts that the capacitance falls by extending the alkyl chain length of cations because neutral segments reduce the packing density of counterions thus the charge density. The side-chain effect is more complicated for ionic liquids in micropores owing to space-charge competition. Adding neutral segments to imidazolium cations always reduces the capacitance in cases where the surface electrical potential of micropores is sufficiently large. However, the capacitance shows a nonmonotonic dependence on the alkyl chain length at intermediate surface potentials. Surprisingly, addition of neutral segments to the cations has the most pronounced effect on the EDL capacitance in cases when the surface potential is positively charged. These findings challenge the conventional assumption that the alkyl side chains of imidazolium ions only negatively impact ionic liquid performance in charge storage.     

The electric double layer effect on the microchannel flow stability and heat transfer

The effect of the electric double layer (EDL) on the linear stability of Poiseuille planar channel flow is reported. It is shown that the EDL destabilises the linear modes, and that the critical Reynolds number decreases significantly when the thickness of the double layer becomes comparable with the height of the channel. First results coming from direct numerical simulations on the non-linear effects show also that the by-pass transition is much more rapid in the presence of EDL. There is an acceptable qualitative correspondence between the estimated transitional Reynolds numbers and some experiments, showing that early transition is plausible in microchannels under some conditions. Several questions remain however unanswered such as the surface conduction effect on EDL.     

Electrooptic effect of water in electric double layer at interface of GaN electrode

We determined the Pockels constant of water in the electric double layer (EDL) at the GaN electrode interface. For a positive (negative) bias, the difference transmittance showed a blue (red) shift in the interference fringes in the visible. This was caused by a negative (positive) refractive index change both in the EDL of water and in the space charge layer (SCL) of the GaN. The latter was associated with the blue shift in the absorption edge in the UV due to the band population effect in the GaN. The voltage drops took place within the interfacial layer at a ratio of about 3: 1 for the SCL vs EDL at the modulation frequency of f = 20 Hz, estimated from the frequency dependence of the impedance. The Pockels constant of water in the EDL was determined to be r ₁₃ = 0:63 × 100 pm/V for the GaN electrodes. This is three times smaller than that at the surface of the indium tin oxide (ITO) electrode.     

The effect of uni/bipolar charge injection on EHD conduction pumping

Electrohydrodynamics (EHD) conduction pumping takes advantage of Coulomb force generated by externally applied electric field and dissociated charges from electrolytes present in the working fluid. With the electric field maintained below the DC breakdown limit (i.e voltage required for charge injection), EHD conduction generated flow relies primarily upon the asymmetry of the electrodes where the flow is always generated toward the specific direction regardless of the electrodes polarity. The charge distribution induced by the process of dissociation may be altered by charge injection, potentially present at the electrodes' surfaces. The charge injection could occur, for example, because of the electrode surface roughness.This paper is a numerical investigation to quantify the impact of the charge injection on the performance of EHD conduction pump. The numerical domain comprises a coplanar asymmetric electrode pair embedded against a 2-D channel wall where the EHD conduction induced liquid flow is expected to be generated from the narrower electrode toward the wider electrode in the absence of charge injection. The electric field, net charge density, and electric body force distributions are presented in the absence and presence of charge injection. In addition, the electrically generated net flow is calculated for several operating conditions.     

TEA CO2激光器均匀场电极的设计

介绍了与此有关的大面积均匀场放电电极的设计以及实验研究结果。无限大平行平板电极两极间的电场分布是均匀的,而现实的问题则是要求在有限的（电极）尺寸条件下实现电场的均匀性设计,因此设计问题转变为放电电极的剖面形状的理论和工程计算问题。根据TEA CO₂激光器工作的实际情况,有针对性地选择Chang氏理论作为设计依据。设计的放电电极实验结果证明,TEA CO2激光器在500HZ高重频脉冲条件下能够连续工作10分钟,在55mm放电电极宽和平坦部分为40mm剖面的平行平板两个主放电极之间实现了大面积稳定的均匀场辉光放电。     

Kinetics of electrochemical reactions: from single crystals to nm-sized supported particles

The rate of electrochemical reactions including electron transfer is influenced by the electric field near the electrode(s). Scrutinizing this effect, we show that the dependence of the electric field near the flat single-crystal electrode on adsorbate coverage may result in increase (up to one order of magnitude) of a rate constant of electrochemical reaction with increasing coverage. In addition, we demonstrate that due to specific distribution of the electric field the rate of electrochemical reaction occurring on supported nm-sized metal particles may be higher (by a factor of 5) than on the flat surface. Finally, we briefly discuss the implications of these findings for interpretation of experimental data.     

迁移率对单层有机发光器件中电场与载流子分布的影响

有机发光器件的宏观特性与有机层中的电场和载流子浓度分布密切相关。建立的有机电致发光器件模型是由两个金属电极中间夹一层有机发光薄膜材料组成的单层器件,金属与有机发光层之间为欧姆接触。模型以载流子运动的扩散-漂移理论为基础,利用数值方法研究了有机发光层中双极载流子注入时的电势、电场、载流子浓度和复合密度分布。分析结果表明:当两种载流子的迁移率相同时,电场强度、载流子浓度、复合密度的分布呈对称形式。而当电子和空穴的迁移率μn和μp相差比较大时,高迁移率的载流子不仅仅分布在注入端附近而且还有一小部分能够传输到另一端,而低迁移率的载流子只分布在其注入端附近;当μn、μp的大小相差不大时,载流子传输情况就介于两者之间。当μn/μp的比值变化时,电场强度的极大值向载流子迁移率小的注入端偏移。