导电岛微电极系统中纳米线介电组装行为研究

为了获得导电岛微电极系统中纳米线的介电组装特性,基于平面微电极对和导电岛微电极系统,进行了两种系统中纳米线操控的对比实验。分别建立了平面微电极对和导电岛微电极系统的纳米线介电组装模型,探究了两种模型下的纳米线从初始位置到最终桥接上微间隙过程中的运动轨迹;分析了导电岛微电极系统中纳米线所受的介电泳力、交流电热流以及两者合作用的电动力学行为。导电岛微电极系统对纳米线有着较强的介电俘获作用,导电岛的加入能够让纳米线更好地俘获到微间隙;同时纳米线的介电组装会受到频率的影响,当频率达到翻转频率,在微间隙上方产生的微流体漩涡能够把远场区域纳米线输送到组装区,使得纳米线受到正介电泳力的作用而被组装至微间隙。     

基于介电泳机理的金纳米颗粒传感器装配方法

研究了一种基于介电泳机理的金纳米颗粒传感器装配方法。在分析介电泳工作原理的基础上,利用Comsol Multiphysics仿真软件,对平面微电极条件下所产生的空间电场进行了建模仿真,研究了金纳米粒子极化模型及相关介电泳频谱特性。设计加工了基于光刻标准工艺和引线键合技术的平面微电极阵列,构建了具有三维位移平台和视频监控装置的介电泳装配实验平台。以250nm金颗粒为实验对象,在理论分析基础上,完成了在微电极阵列上的介电泳组装实验研究,并通过电特性测量验证了组装结果。实验结果表明:金纳米颗粒的介电泳组装效果与介质溶液的电导率、电场频率和幅度、金纳米粒子浓度、电极间隙及作用时间有关,在适宜的条件下,采用介电泳技术可实现对金纳米颗粒的有效操控和纳米器件装配,该方法为纳米传感器的制造提供了一种有效途径。     

基于行波介电泳的细菌分离电极的设计与操控北大核心

基于行波介电泳原理,分析了电场强度和Clausius-Mossoti(C-M)因子的虚部对行波介电泳力的影响。对4种不同形状电极的电场强度分布进行了仿真建模,结果表明半圆形电极阵列有较好的传输特性,并建立了半圆形电极阵列在行波作用下的电场模型。以行波介电泳力的复数表达式为基础,得出了C-M因子虚部随频率的变化曲线。设计加工了基于半圆形电极阵列的细胞分离微流体芯片,基于行波介电泳原理,对金黄色葡萄球菌细菌进行了分离实验。通过对比分析,实验结果与仿真结果具有较好的一致性。因此,利用行波介电泳力,半圆形电极阵列能够有效地对细菌进行传输分离。     

碳纳米管介电电泳组装及过程控制研究进展

碳纳米管具有独特的结构和卓越的电学、热学、力学等性能,有望在微纳电子、微纳机电系统、传感器、新能源、光学等诸多领域获得具有深远影响的应用。碳纳米管的组装是其获得广泛应用的重要前提,基于介电电泳的组装和过程控制技术近年来得到了迅速发展。这些技术包括回路中串联自限制性电阻,间隙电信号实时监测和反馈控制,三维结构的组装和包覆,引入不同形状浮动电极等。对碳纳米管介电电泳组装及各种新技术做了系统介绍,并对各种方法的优缺点进行了对比与总结,为探索稳定、高效的碳纳米管自动组装方法提供帮助。     

基于介电泳技术制备SiC纳米线薄膜晶体管

本文从理论和实验两方面,研究了介电泳技术中SiC纳米线溶剂的选择。从介电泳力、介电泳力矩、溶剂的挥发性和毒性角度分析,发现异丙醇是合适的SiC纳米线溶剂。以异丙醇作为溶剂,利用介电泳技术实现了SiC纳米线的定向排列,并得到纳米线薄膜。SiC纳米线溶液浓度分别为0.1μg/μL,0.3μg/μL, 0.5μg/μL时,得到定向排列纳米线的密度分别为 2/μm,4/μm,6/μm。并且利用密度为6/μm的SiC纳米线薄膜制备了晶体管,该晶体管的迁移率为13.4 cm2/V?s。     

锗纳米线的性能与应用

重点分析讨论了锗纳米线在电学、光学、光电导等特性及其在场效应晶体管制造方面的研究应用现状与最新进展。综合分析表明,未经处理的锗纳米线表面存在一层氧化物及缺陷,与电极连接时欧姆接触性能较差,在制备锗纳米线器件以前必须对锗纳米线表面进行钝化以便沉积电极;对锗纳米线进行掺杂可以改善Ge纳米线的性能,制造出实用Ge纳米线器件。指出在一根纳米线上生长硅/锗半导体纳米线形成硅/锗半导体界面,直接用单根纳米线制造具有完整功能的电子器件是将来重要的研究方向。     

锗纳米线的性能与应用

重点分析讨论了锗纳米线在电学、光学、光电导等特性及其在场效应晶体管制造方面的研究应用现状与最新进展。综合分析表明,未经处理的锗纳米线表面存在一层氧化物及缺陷,与电极连接时欧姆接触性能较差,在制备锗纳米线器件以前必须对锗纳米线表面进行钝化以便沉积电极;对锗纳米线进行掺杂可以改善Ge纳米线的性能,制造出实用Ge纳米线器件。指出在一根纳米线上生长硅/锗半导体纳米线形成硅/锗半导体界面,直接用单根纳米线制造具有完整功能的电子器件是将来重要的研究方向。     

碳纳米管非对称接触结构制作及电学性能研究

实验研究了多根或单根单壁碳纳米管与非对称金属电极接触结构的制作方法。先用介电泳方法(DEP)将碳纳米管定向排列在Au电极对之间,再用电子束光刻(EBL)在碳纳米管的一端加工Al电极,获得多根碳纳米管与金铝电极的非对称接触结构。先用EBL在Au电极对一端覆盖Al电极,再用DEP排列碳纳米管,实现单根碳管与金铝电极的非对称接触结构。非对称结构器件的电学测试研究表明,器件的I-V曲线不再对称,呈现出整流特性。     

电气和电子工程用材料科学

TN04 2002060021一维纳米材料的合成、组装与器件/董亚杰,李亚栋(清华大学)11科学通报.一2002,47(9)一641一649一维纳米材料的合成、组装及其物性的测量是制约其在纳米原型器件制作与应用中的关键,评述了这一领域的最新进展.一维纳米材料的组装大致可分为宏观场力组装与微流输助模板限域组装,其中前者是通过控制宏观电场、磁场的方向和大小来对微观的纳米线进行组装,后者则通过控制模板的形状、尺寸、流体的流速、沉积的时间等来实现纳米线网络阵列的制备.纳米线的组装与单根纳米线的物性测量使得纳米线激光器、传感器乃至纳米逻辑电路的制…     

集成阵列叉指电极介电泳芯片粒子分离北大核心

制备了用于粒子分离的集成阵列叉指电极介电泳微流控芯片,该芯片由以玻璃为基底的氧化铟锡(ITO)电极以及聚二甲基硅氧烷(PDMS)微流通道构成。采用该芯片测定了聚苯乙烯微球在电导率为1μS/cm的悬浮溶液中在不同频率下的介电泳响应。聚苯乙烯微球产生正负介电泳响应的临界频率为20 kHz。当交流电压和频率分别为8Vp-p(峰峰值)和2 MHz时获得最优的粒子分离条件,在此条件下对聚苯乙烯微球和酵母菌细胞进行分离实验。实验结果表明,酵母菌细胞受到正介电泳力的作用,被富集到电极的边缘,而聚苯乙烯微球受到负介电泳力的作用被排斥而远离电极,其分离效率能够达到90%。     

Manipulation of microparticles using new modes of traveling-wave-dielectrophoretic forces: numerical Simulation and experiments

This paper presents a microchip device which uses traveling-wave-dielectrophoretic (twDEP) forces for the manipulation of microparticles and yeast cells. The dielectrophoretic forces generated under different operating conditions are simulated numerically, and the electric field distributions, force distributions and microparticle traces are investigated thoroughly. The paper presents two innovative modes of microparticle manipulation using positive (only one electrode is active at any instant in time, while the other three electrodes are all switched off) and negative (one electrode is "off", and the other electrodes are "on") dielectrophoretic forces. Micromachining techniques are used to fabricate micro-twDEP chips. The capability of electrode arrays in manipulating bioparticles is demonstrated by driving yeast cells in a suspension medium. The current experimental data confirm that dielectrophoretic forces can be used successfully for the collection, alignment, step-wise movement and general manipulation of cells.     

准分子激光器中张氏面型电极的电场仿真研究

为了获得准分子激光器高脉冲能量输出,采用张氏面型电极的理论,设计了一套能产生大面积均匀电场的紧凑型电极。通过ANSYS软件数值仿真获得了电极表面电场分布,并与紧凑型张氏面型电极的理论计算结果进行了对比验证;分析了紫外火花预电离结构对电极放电的影响,并进行了电位和电场分布仿真。结果表明,预电离板的存在直接影响了电极之间的电位和电场分布;电场仿真结果解释了预电离板的顶端与阳极形成放电的原因。该研究为大面积辉光放电电极设计提供了更深入的理论支持。     

Nanopatterned platinum electrodes by focused ion beam in single palladium nanowire based devices

In this paper we present different devices, working as hydrogen sensors, based on single palladium nanowire and realized combining focused ion beam and dielectrophoresis techniques. The combination of these two techniques consists in the employ of focused ion beam for electrode patterning onto silicon/silicon dioxide substrates, followed by the assembly of a single palladium nanowire applying between electrodes an electric field at fixed frequency (dielectrophoresis) to a palladium nanoparticles solution. The nanowire morphology can be branched or not, depending on the applied frequency value. The devices are characterized in hydrogen environment at room temperature and their responses are compared.     

A study on three-dimensional electrode arrays fabricated by PolyMUMPs® for AC electro-osmotic pumping

This paper presents four three-dimensional (3D) micro-electrode arrays for pumping liquid by utilizing AC electro-osmosis (ACEO) mechanism. Fabricated by using PolyMUMPs® process, these electrode arrays are made of polysilicon and subject to a surface oxide layer, which does not exist on conventional gold electrodes. An ACEO finite element model (FEM) accounting for the surface oxide on polysilicon electrodes is integrated in this work. The relationship of the velocity of driven liquid vs. the frequency of the electrical driving signal is obtained for the four electrode arrays through simulation and testing. Impacts of the electrode configuration and surface oxide are analyzed by comparing simulation and experimental results.     

Electrodynamically actuated on-chip flow cytometry with low shear stress for electro-osmosis based sorting using low conductive medium

In the proposed paper, we demonstrate on-chip electrodynamically driven actuator flow cytometry, based on negative dielectrophoretic (nDEP) focus and alternating current electro-osmotic flow (ACEOF) sorting technique. This single chip can perform three different functions such as focusing, transportation of beads/cells to detection site and reloading the unsorted ones with two distinctive phenomena. AC EOF is achieved by the design of the asymmetric electrode pair’s array and nDEP is used to focus the beads/cells in-line. The design, simulation and experimental results of the proposed microchip are reported in this paper. The simulation and experimental results reveal well defined stable region for nDEP and ACEOF driving force. The potential severe shear stress damage caused by the sheath flow in conventional flow cytometry is eliminated. In addition, to explore the influence of conductivity of the medium, we have used low conductive formulated medium with conductivity of 81.4 μS/cm. The voltage and the frequency required to manipulate the particles decreased comparatively with the use of this medium.     

Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ～5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2‐D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter‐wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter‐wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires.     

Investigation of The Effects of Contact Forces Acting on Rollers Of a Mecanum Wheeled Robot

In this study, the effects of contact forces on the rollers of a mecanum wheeled robot are investigated. Modeling structures are constructed for the cases of single and multiple contact forces. A simulation environment is developed to examine these two cases. A theoretical model is proposed in order to reflect reality in the simulation environment. It is shown that single contact force assumption generates vertical vibration in a mecanum wheeled robot which is never desired in a real application. It is also demonstrated that adding more contact forces on a roller of a mecanum wheel's model decreases the transition distance between the rollers and thus creates smaller vibrations. An experimental setup, containing a four wheeled mecanum robot, is designed and built, and used for performing experiments to make verifications. Reference trajectory, simulation results obtained using single and multiple contact force cases and the experimental results are presented together to make comparisons. The details of the model proposed, simulation environment developed, experimental system designed and the results obtained are given in this paper.     

Four-Wire Resistance Measurements of a Bismuth Nanowire Encased in a Quartz Template Utilizing Focused Ion Beam Processing

Four-wire resistance measurements were performed using a bismuth nanowire, 750?nm in diameter, 1.96?mm in length, and encapsulated in a quartz template. One side of the quartz template was polished to allow focused ion beam (FIB) processing, and metal film layers were deposited on the polished side to form electrodes. Nanofabrication was employed to remove a selected portion of the quartz, and FIB processing was used to expose the surface of the bismuth nanowire. A local area of the bismuth wire was successfully exposed, and a carbon electrode was deposited on the bismuth wire in?situ by a chemical reaction between the ion beam and phenanthrene gas. Additional carbon deposition on the initial carbon electrode was used to connect to a metal film on the quartz template. In total, four nanofabrications were performed on the bismuth wire to create the desired electrical contacts. The resistivity of the nanowire was measured by a four-wire method to be 1.29??????m at 300?K, corresponding to that of bulk bismuth. The temperature dependence of the resistivity was also measured, and was qualitatively and quantitatively in good agreement with previous calculated and experimental results using other bismuth nanowires. The present results demonstrate the successful development of a technique to fabricate an electrode on a local area of a nanowire using FIB processing to form suitable electrical contacts.     

A new low-temperature bonding technology between large-area,high-power devices and Mo electrodes using Au-Al films

In order to realize large-area, high-power devices with high-performance, low-temperature diffusion, bonding technology between Al electrodes on both cathode and anode sides of Si devices and Mo electrode foils has been investigated, The 100 mm diameter power devices and the same size Mo foils could be joined by the formation of Au-Al intermetallic compounds below 573 K. The compounds were formed by solid state diffusion with activation energy of about 1.0 eV. Substantial reduction of the mounting force while keeping uniform contact was possible after low-temperature bonding. Reliability of the bonded large area, high-power device was predicted to be sufficient from a metallurgical viewpoint