基于介质上电润湿的钳制式液体变焦透镜

提出了一种基于介质上电润湿(EWOD)的新型液体变焦透镜结构并研制出样机。它由一个依次覆盖有氧化铟锡(ITO)透明导电薄膜及疏水介质膜的玻璃下极板、悬浮于其上方的一个中空金属环、以及作为透镜的去离子水滴组成。通过改变施加于ITO电极与金属环之间的电压大小,就能调控水滴的曲率,从而实现对透镜焦距的调节。实验结果表明,在0~40V电压范围内,该透镜样机的焦距调节范围为8.51mm至55.9mm,可实现对2.0cm至无穷远处物体的聚焦。     

基于介质上电润湿的平面可变焦液体微透镜*

在现代光学技术中,可变焦微透镜被越来越广泛的使用.在提出的各种新型的可变焦微透镜技术中,基于介质上电润湿的微流体透镜由于其结构简单、功耗低、调节焦距方便等众多突出的优点而被人们所重视.本文中研制出一种基于介质上电润湿的平面微透镜结构,它不仅能控制改变焦距,还能实现透镜在平面上的横向运动.     

透明导电薄膜ITO对GaN基蓝光发光二极管影响的分析

本论文通过正交试验对透明导电薄膜ITO蒸发厚度、退火温度、退火时间及退火时N2流量进行研究,并将制备的透明电极ITO薄膜应用于GaN基发光二极管,分析其对管芯表面电流扩展、ITO与P-GaN欧姆接触电阻的影响,通过优化ITO相关工艺来降低LED工作电压及提高透过率、提高LED发光亮度。通过试验得到优化参数为:ITO厚度250nm,火温度400℃,N2流量30L/min,火时间10min。在优化条件下玻璃片上测得ITO方块电阻约为12Ω/□,透光率达到95%以上,制得的203μm×508μm蓝光LED芯片在直流电流20mA下的正向电压3.18V,光功率为26.11mW。封装成X=0.35,Y=0.35,色温4500K,显色指数75白光后,光通量为7.81lm。     

耐腐蚀液位监控仪

1.工作原理众所周知,酸、碱溶液和一些不燃性混合液体是具有导电性能的,这些介质可以视为低阻导体。在被测介质的贮罐(贮槽)中放置一个测量筒,筒体上设置有若干个上下排列的电极,在筒体最低部安装一个公共电极作为信号源(此端带有一个信号电压)。当被测介质液位上升或下降时,其点电极也相应地被介质浸没或露在液面上,公共电极通过介质向被浸没的电极送入信号电压,电极又把此信号电压送到显示仪表。工作原理方框图如图1所示。由此可见,被测介质与电极之间就相当于一个"开关",液位上升或下降,"开关"就会随之导通或断开,显示仪表的液位显示灯就会"亮"或"灭"。     

电场中导电液滴电场效应的数值模拟

为研究低电导率导电液滴的电场效应,采用开源计算流体力学(CFD)软件OpenFOAM,设计了一种基于漏介质模型(leaky dielectric model)和流体体积(volume of fluid, VOF)法的电流体雾化(electrohydrodynamic atomization, EHDA)求解器,并将数值结果与Taylor的解析值进行了比较.模拟结果预测了液滴的变形方式以及液滴内外的环流模式.研究发现,在外加电场作用下,液滴会发生“扁长型”或“扁圆型”变形,并在内部形成稳定的环流,液滴只会发生变形,而不会发生宏观运动;随着电场强度的增加,液滴的变形越来越大,小变形情况下,模拟值与理论值基本吻合,验证了数值方法的正确性;当液滴的变形量较大时,模拟结果开始偏离理论值,与实验观察结果一致.此外,电导率比值的改变对液滴变形的影响也比较明显,而介电常数比的改变对液滴变形的影响则不太明显.     

氯化钠液滴在特氟龙表面润湿行为的电控调节研究

为进一步探究界面润湿行为的电控调节机理,掌握电场调控的影响规律,基于能量最小原理和液滴体积不变原则,构建了多因素耦合的介电润湿等效模型,对比分析了加载电压大小、极性、频率变化对氯化钠液滴在特氟龙表面浸润特性的影响.由理论分析和实验测试表明:在0～±70 V范围内,无论是施加正向还是负向电压,接触角均会随电压增大而呈现非...     

直流电压下基于电液耦合动力学原理的微喷试验研究

基于直流电压作用下的电液耦合微喷印系统,考察了溶液浓度和电压两个参数对喷印过程和沉积形态的影响.实验结果表明射流在收集板上沉积的宽度随溶液浓度增大而减小;浓度低时射流沉积为连续形态;浓度增大,射流沉积为液滴-细线相间或者液滴-卫星液滴相间的珠状结构;浓度增大至18 %时,产生纳米纤维,直径600 nm左右.对给定的EHD实验系统,仅当电压值在2.6 kV~4.8 kV范围内变化时可保证稳定喷射;且随着电压值增大,珠状结构的直径减小;电压值在该范围之外,无法实现稳定喷射.     

基于语法树的实时动态电压调节低功耗算法

动态电压调节是一种有效的低功耗技术.使用这种技术,编译器指导的动态电压调节能够有效地降低系统功耗.提出了基于语言语法树的实时动态电压调节低功耗算法.该算法在静态程序最差时间分析方法的辅助下,通过在程序内部自动插入电压调节代码来实现电压调节.在RTLPower(real-time low-power)实时低功耗系统上完成了算法的实现,对嵌入式测试,程序集的初步测试证明该算法最大可节省50%的能量消耗.     

煤介质阻挡放电脱硫的影响因素分析

依据介质阻挡放电理论,对原煤进行煤介质阻挡放电脱硫实验。实验结果表明,煤介质阻挡放电脱硫的影响因素与电极结构、介质成分和气隙距离等因素有关,如将介质放到放电间隙中间时脱硫的效果没有将介质直接放在放电极板上的脱硫效果好,加煤的情况下微放电的强度明显大于不加煤的微放电过程强度;脱硫效果呈"U"字型变化,由此推论,在一定的外界条件下,煤介质阻挡放电除硫有一个最佳的施加电压;随着电压的增加,放电脉冲的相位范围逐渐扩展。     

RTLPoWer：一个实时动态电压调节低功耗系统

功耗问题是计算机系统发展亟待解决的问题,硬件和软件在解决功耗问题上都有重要的作用.尽管有许多工具可用于低功耗硬件的开发,但支持软件技术开发的低功耗工具并不多见.我们基于ARM的指令集开发了一个实时动态电压调节低功耗系统RTLPower.RTLPower综合了编译指导的动态电压调节和程序的性能功耗模拟,该系统能够有效支持编译指导的动态电压调节技术的研究开发.     

Room‐temperature deposition of thin‐film indium tin oxide on micro‐fabricated color filters and its application to flat‐panel displays

Abstract— Direct deposition of indium tin oxide (ITO) thin film on color filters is of practical use in the fabrication of state‐of‐the‐art flat‐panel displays. Room‐temperature dc magnetron sputtering of thin‐film ITO and issues related to the integration of ITO‐on‐glass panels containing micro‐fabricated color filters and other functional materials have been investigated. The resulting polycrystalline ITO exhibited good adhesion to the underlying color filters, as well as good optical transparency and high electrical conductivity. Application of this ITO deposition technology to color liquid‐crystal and organic light‐emitting diode displays will also presented.     

Numerical simulation of emergence of a water droplet from a pore into a microchannel gas stream

A numerical investigation on the dynamic behavior of liquid water entering a microchannel through a lateral opening (pore) in the wall is reported in this paper. The channel dimensions, flow conditions and transport properties are chosen to simulate those in the gas channel of a typical proton exchange membrane fuel cell (PEMFC). Two-dimensional transient simulations employing the volume of fluid method are used to explicitly track the liquid–gas interface, and to gain understanding into the dynamics of a water droplet subjected to airflow in the bulk of the microchannel. A series of parametric studies, including the effects of static contact angle, dimensions of the pore, air-inlet velocity, and water-inlet velocity are performed with a particular focus on the effect of hydrophobicity. The simulations show that the wettability of the microchannel surface has a major impact on the dynamics of the water droplet. Flow patterns are presented and analyzed showing the splitting of a droplet for a hydrophobic surface, and the tendency for spreading and film flow formation for a hydrophilic surface. The time evolution of the advancing and receding contact angles of the droplet are found to be sensitive to the wettability when the gas diffusion layer surface is hydrophilic, but independent of wettability when the surface is hydrophobic. The critical air velocity at which a droplet detaches is found to decrease with increasing hydrophobicity and with increasing initial dimension of the droplet. The critical air velocity found in the present study by taking into account the water transport and evolution of the droplet from a pore are found to differ significantly from previous works which consider a stagnant droplet sitting on the surface.     

A new liquid crystal lens with axis-tunability via three sector electrodes

A novel liquid crystal (LC) lens with an on-line tunability on focus length and optical axis is proposed in this study. The designed lens has a LC layer sandwiched by two ITO glasses, one of which is patterned with three sector electrodes. With varied sets of pre-designed voltages applied to these three electrodes, the LC lens can not only render focusing effects but also tunability on the optical axis of the lens to an arbitrary axis. A vector-form equation is developed to predict the direction of axis tuning. Simulations are next conducted to predict dynamics of the LCs in the lens and also the focusing and axis-tuning properties of the lens. Important sizes and materials and fabrication process of the lens are determined and optimized based on simulation results. The designed LC lens is fabricated, and then experiments are conducted to demonstrate the performance of the designed LC lens on axis tuning. It shows that the focusing axis of the LC lens can be effectively changed by pre-calculated combinations of three voltages. It is also shown that the average movement of the focal point per applied voltage reaches 4.778?μm/V.     

Flow resistance of a liquid droplet confined between two hydrophobic surfaces

Flow resistance of a liquid droplet confined between two hydrophobic surfaces has been investigated experimentally and factors contributing to the flow resistance have been studied. A water droplet has been sheared between two hydrophobic surfaces and shear resistance has been measured. The experimental results show that the shear resistance at low shear velocities is primarily caused by asymmetrical surface tension due to the contact angle hysteresis. A droplet on a rough hydrophobic surface remains almost symmetrical under shear and exhibits extremely low friction. The shear resistance at high shear velocities is affected by viscous force. Furthermore, sliding angles of water droplets on micropatterned hydrophobic surfaces have been measured to clarify the effects of surface topography on flow resistance. Surfaces with many prismatic structures raised out of the plane tend to exhibit low sliding angles.     

Miniaturized variable-focus lens fabrication using liquid filling technique

This paper describes a simple method for fabricating a variable-focus lens using polydimethylsiloxane (PDMS) filling with liquid to produce a variable-focus lens. A 2-mm diameter lens was designed in this experiment, expected to reach a focal length in the range of 3 ∼ 12 mm. The theoretical value between the liquid volume and the lens contact angle at different focal lengths were simulated and measured. The pumped-in liquid volumes ranged from 200 to 1,400 μl. The contact angles ranged from 14.25° to 49.02°. Variable focal length was produced by changing the PDMS film deformation using different micro-fluidic volumes. The focal length produce in the experiment was from 4 ∼ 10 mm. The proposed method successfully fabricated a variable-focus lens. Bonding PDMS only once using no expensive instrument such as oxygen plasma was accomplished. The final objective is to insert the variable focus lens into portable optical imagery products.     

Thin-film electrode based droplet detection for microfluidic systems

We report on a droplet-producing microfluidic system with electrical impedance-based detection. The microfluidic devices are made of polydimethylsiloxane (PDMS) and glass with thin film electrodes connected to an impedance-monitoring circuit. Immiscible fluids containing the hydrophobic and hydrophilic phases are injected with syringe pumps and spontaneously break into water-in-oil droplet trains. When a droplet passes between a pair of electrodes in a medium having different electrical conductivity, the resulting impedance change signals the presence of the particle for closed-loop feedback during processing. The circuit produces a digital pulse for input into a computer control system. The droplet detector allows estimation of a droplet's arrival time at the microfluidic chip outlet for dispensing applications. Droplet detection is required in applications that count, sort, and direct microfluidic droplets. Because of their low cost and simplicity, microelectrode-based droplet detection techniques should find applications in digital microfluidics and in three-dimensional printing technology for rapid prototyping and biotechnology.     

Propulsion of droplets on micro- and sub-micron ratchet surfaces in the Leidenfrost temperature regime

Spatially periodic systems with localized asymmetric surface structures (ratchets) can induce directed transport of matter (liquid/particles) in the absence of net force. Here, we show that propulsion for the directed motion of water droplets levitating on heated ratchet surfaces in the Leidenfrost (film boiling) regime is significantly enhanced as the ratchet period decreases down to micro- and sub-micrometers. At the temperature range slightly above the threshold temperature of droplet motion, sub-micron ratchets yield water droplet velocities reaching ~40 cm/s, a speed that has never been achieved with any chemical and topological gradient surfaces. This dramatic increase in the droplet velocity is attributed to an enhanced heat transfer through the local contacts between ratchet peaks and bottom of the droplet. A hydrophobic coating on the ratchet surfaces is found to further increase the droplet velocity and decrease the threshold temperature of the droplet motion. The results suggest that miniaturized ratchet surfaces can potentially be used in diverse applications requiring control over fluid transport and heat transfer such as two phase cooling systems for microprocessors and fuel injection for combustion technology and that for those applications the design of ratchet dimensions and surface chemistry are critically important.     

Reflecting electrochromic devices

Unstructured all-solid-state thin-film electrochromic devices (ASTFEDs) with variable reflectance have been developed on the basis of hydrogen-tungsten bronzes. The characteristic compounds of these systems are a transparent electrode (ITO), an electrochromic WO₃-layer, solid-state ion-conducting layers (‘electrolytes’), an integrated reflecting layer, and a hydrogen-storing layer. The total thickness of such structures is only a few microns. They are enclosed between the substrate glass and a second glass plate and are thus protected from the environment. Different modes of construction are presented and compared, the electrochemistry of the thin-layer cells is discussed, the tasks and characteristics of the thin-film arrangements and their important features are shown, and possible applications are briefly described.     

Contactless sensing of the conductivity of aqueous droplets in segmented flow

We present an electrode arrangement for the inline measurement of the conductivity of droplets in segmented flow by impedance spectroscopy. We use a thin-walled glass capillary with electrodes contacting the outer surface, so that the contactless measurement of conductivity of the liquid within the capillary is possible. The surface of the glass capillary is silanized resulting in a single hydrophobic surface across which droplets can freely move. We model the impedance of such insulated electrodes and use the model to optimize the electrode system. Measurement of solutions with various salt concentrations allows the performance of the electrode structure to be characterized. Subsequently, the measurement of the impedance response of the aqueous segments in two-phase flow was demonstrated. Measurements were firstly performed with an impedance analyzer and subsequently with a multi-sine measurement setup that is better suited to high-speed measurement of droplets. Previous electrical measurements of segmented flow sensed the difference in dielectric constant between the aqueous phase and the carrier fluid through measurement of capacitance. This work describes an electrical measurement of the conductivity of droplets in segmented flow, that is, the sensor senses a variable property of the droplet itself.