共查询到20条相似文献,搜索用时 46 毫秒
1.
The ability to achieve fast fluid flow yet maintain a relatively low temperature rise is important for AC electrothermal (ACET)
micropumping, especially in applications such as bioMEMS and lab-on-a-chip systems. In this paper, we propose a two-phase
ACET fluidic micropump using a coplanar asymmetric electrode array. The proposed structure applies a two-phase AC voltage,
i.e., voltage of phase 0°/180°, to the narrow electrodes while the wide electrodes are at ground potential. Numerical simulation
demonstrates that this simple coplanar electrode configuration can achieve at least 25% faster fluid flow rates than using
a single AC signal. By selecting certain design parameters, a two-phase ACET structure can achieve up to 50% faster fluid
flow rates than a corresponding single-phase structure. The simple two-phase AC signal sources are easily produced by using
inverter buffers, which is a considerable improvement compared to the multi-phase AC signals required by other electrokinetic
micropumping methods, such as traveling wave structures. 相似文献
2.
使用交流电化学方法定向制备了预制微电极之间的电连接。通过调节交流电压与偏置直流电压幅值可以控制电连接的生长方向。如果施加的交流电压幅值高于生成电连接的电压阈值,并且该值恒定时,频率越小,浓度越大,电连接晶体越粗壮;而当电解液浓度与频率恒定时,电压幅值变化对形貌影响较小。有限元仿真模拟进一步说明:当施加的交流电压高于阈值时,电极处于交流电渗流上游。电极扩散层厚度增加将诱导电极之间电连接晶体的生长。在交流电压上叠加直流偏置电压时,电连接晶体从偏置电压相对较负的一端向另一端生长。伏安特性测试结果表明:该连接具有优异的接触特性。 相似文献
3.
Hukun Yang Hongyuan Jiang Antonio Ramos Pablo García-Sánchez 《Microfluidics and nanofluidics》2009,7(6):767-772
AC electro-osmotic (ACEO) pumping is experimentally demonstrated on a symmetric gold electrode array. Using asymmetric connection
of electrodes to the applied AC voltage, spatial asymmetry along the array is created, which produces unidirectional flow
of electrolyte. An aqueous solution of 100 μM KCl is selected as the pumping fluid. The liquid velocity obtained as a function
of voltage and frequency is compared to that generated using travelling-wave electroosmosis (TWEO) with the same electrode
array. The expected velocities from the linear electrokinetic models of ACEO and TWEO are computed numerically. The comparison
shows that TWEO generates greater velocity amplitudes and the streamlines are smoother than those generated by ACEO. 相似文献
4.
5.
Point-of-care (POC) diagnostics is one of the most important applications for microfluidic research. However, the development of microfluidic POC devices needs to overcome great obstacles to reach market. One challenge is to find a chip-scale pumping strategy that is of low cost, small size, and light weight. Because of their simple implementation, electrokinetic techniques have been extensively investigated as a promising candidate for realizing disposable pumps, with the majority of research effort focusing on direct current and alternating current (AC) electroosmosis. As POC applications often need to handle conductive biofluids with medium to high salt content, AC electrothermal (ACET) effect has been investigated recently for pumping of biofluids, albeit with less than desirable pumping performance. In order to achieve effective on-chip ACET micropumps, this paper presents one of the first efforts in optimizing ACET micropump design utilizing planar interdigitated electrodes. The effects of electrode dimensions on pumping rate were numerically studied using COMSOL Multiphysics and MATLAB, and an optimal ratio of electrode geometry was found for various pumping scenarios. The optimal geometry ratio was tested to be valid over a wide range of electrode characteristic lengths, AC signals, and fluid ionic strengths. Experimental validation of the simulation results was also conducted, and higher flow velocities over prior reports were consistently demonstrated by optimized electrode arrays. 相似文献
6.
DC/DC converters are widely used in consumer electronic devices where usually a single power source is available while the electronic board of the device requires different voltage levels in order to power-up different block functions. In this paper we present the design of a MEMS single-input multi-output voltage level shifter. The low-voltage to high-voltage conversion is based on the electrostatic transduction of variable capacitors built using interdigitated comb fingers. A 1?mm2 MEMS prototype has been designed and fabricated using the SOIMUMPs process. In this study we present the co-design and co-simulation of the whole system (the MEMS device and its dedicated charge-pump-circuit) in a single EDA environment through MEMS+ (a Coventorware? tool that allows the co-simulation of MEMS and electronics in the Cadence Analog Design Environment). We present analytical, FEM and MEMS+ models of the multi-output DC–DC converter and show that all our models converge towards the experimental results. 相似文献
7.
Neophytos Loucaides Antonio Ramos George E. Georghiou 《Microfluidics and nanofluidics》2007,3(6):709-714
In this paper we present a novel method of creating and using geometric asymmetries for AC electroosmotic pumping. The method
relies on grouping similar electrodes together in terms of applied voltage, in order to create configurable asymmetries in
periodic electrode arrays, which induce a net pumping AC electroosmotic velocity. Using a numerical model for a system designed
by applying the described method, it is demonstrated that by varying the degree of asymmetry it is possible to control the
direction of the pumping velocity at a given voltage by simple switching of the voltages on the electrodes. 相似文献
8.
为克服发电机局部电压过高导致的电子跳跃问题,提出三相风力发电机的低电压穿越控制方法.建立三相低电压矩阵,对正负序电压进行分量,实现低电压建模操作.再进行三相风力发电机低电压的开关切换,调节基础穿越控制稳定性,选择合适风力发电机逆变器进行低电压穿越调节,实现三相风力发电机的低电压穿越控制.仿真结果表明,随着三相风力发电机... 相似文献
9.
设计了一个双并联电渗驱动泵,它由三条并联的主通道和叉指型电极两部分组成,其中每条主通道由若干个与电渗流形成方向成45°角的沟槽并联构成。通过选用ITO载玻片作为芯片基底并获得其最佳工艺参数,制作了带电极的PDMS-玻璃微流控芯片。最后对制作的电渗微泵进行测试,通过记录一段时间内单个主通道泵输送液体的体积,得出单个主通道的流速与微泵总流速。实验发现在5V内,微泵泵送液体的能力随着电压的增加而增大,微泵流速可以达到正常人体眼球房水生成速度,该结构在未来房水引流器件制作方面具有潜在的应用价值。 相似文献
10.
11.
N. Bogatov Yu. Brodsky S. Golubev 《Journal of the Society for Information Display》2003,11(4):683-690
Abstract— This paper demonstrates that it is possible to improve the basic parameters of plasma displays (efficiency, primarily) using AC voltages with frequencies so high that the amplitude of the electron‐drift oscillations is smaller than the inter‐electrode gap. In this case, the voltage drop on sheaths is much smaller than that in the low frequency or DC discharge and, correspondingly, the energy losses in ion heating are also small. Electron losses in the RF discharge are of the diffusion character and sufficiently lower than the losses in a typical AC plasma‐display panel (AC PDP), in which the electron drift to the electrodes is predominant. Hence, the energy cost of gas ionization in the cells of radio‐frequency PDPs (RF PDPs) is also rather low. In the long run, about 80% of the energy absorbed in the RF discharge goes into excitation of the energy level of a Xe atom, yielding UV radiation. The experiments performed show that efficiency of a RF PDP is five times higher than the efficiency of existing AC PDPs and DC PDPs and can exceed 5 lm/W. 相似文献
12.
电磁流量计极间信号干扰的建模与分析 总被引:1,自引:0,他引:1
电磁流量计极间信号不仅包含流量信号,而且掺杂有各项干扰信号。流量信号和干扰信号都是由相对独立的信号源产生,所以它们之间以物理叠加的关系构成了电磁流量计极间信号。因此将上述信号构建数学模型,经解析:直流分量代表管内水流速度信号,即流量信号。交流分量呈现为干扰信号特征。采用信号分离手段,较容易得到流量信号并去除干扰信号。实验数据表明通过建模分析可以有效地去除电磁流量计极间干扰信号,此方法设计的电磁流量计误差范围比传统的正弦波励磁电磁流量计误差范围小±0.05%。 相似文献
13.
Particle separation in alternating-current electro-osmotic micropumps using field-flow fractionation
Bernhard Weiss Wolfgang Hilber Philipp Gittler Bernhard Jakoby 《Microfluidics and nanofluidics》2009,7(2):191-203
This work presents a novel method for continuous particle separation on the microscale by means of field-flow fractionation.
It is based on the use of asymmetric interdigitated electrode arrays on the channel bottom, which induce an electro-osmotic
channel flow when driven harmonically. Suspended particles are influenced by viscous fluid drag, sedimentation as well as
by dielectrophoretic repulsion forces from the driving electrodes due to the emerging electric field. The significant dependance
of the present forces on particle properties allows for separation with respect to particle density and size. This work analyzes
electric and flow field by means of the finite element method and investigates the size and density dependent particle motion
as a function of driving voltage and frequency of the electrode array. Matching these driving parameters permits the separation
of sedimenting particles by their density independently from their size as well as the separation by size. Finally, channel
designs are proposed which enable standard separation by means of selective particle mobility in the channel, separation in
terms of opposing motion directions, as well as continuous lateral separation. 相似文献
14.
分析了环境湿度大小对高压电使用的影响,设计了一种基于湿度控制的静电式空气净化器高压电源,采用微功率非隔离方式实现AC-DC转换,经过自激推挽式DC-AC升压电路和倍压整流电路获得两路高压输出,通过PIC单片机控制数字电位器X9241控制电压输出。实现了220 V交流电输入,两路电压为5 kV和10 kV的高压输出,并依据采集到的环境湿度信息,自动调节输出电压大小。经试验测试表明,该电源输出电压可控性好、体积小、成本低、功耗低,有效保证了电源在不同湿度环境中的使用安全。 相似文献
15.
Gang‐Youl Jeong 《Journal of the Society for Information Display》2009,17(9):723-734
Abstract— A high‐performance high‐efficiency LED‐backlight driving system for liquid‐crystal‐display panels is presented. The proposed LED‐backlight driving system is composed of a high‐efficiency DC‐DC converter capable of operating over a universal AC input voltage (75–265 V) and a high‐performance LED‐backlight sector‐dimming controller. The high efficiency of the system is achieved by using an asymmetrical half‐bridge DC‐DC converter that utilizes a new voltage‐driven synchronous rectifier and an LED‐backlight sector‐dimming controller. This controller regulates current using lossless power semiconductor switches (MOSFETs). The power semiconductor switches of the proposed DC‐DC converter, including the synchronous rectifier switch, operate with zero voltage, achieving high efficiency and low switch voltage stress using the asymmetrical‐PWM and synchronous rectifier techniques. To achieve high performance, the proposed driving system performs the sector dimming and the current regulation using low‐cost microcontrollers and MOSFET switching, resulting in high contrast and brightness. A100‐W laboratory prototype was built and tested. The experimental results verify the feasibility of the proposed system. 相似文献
16.
何新洲 《计算机测量与控制》2019,27(4):267-270
考虑到目前电量计量采集系统线路布置复杂,针对窃电行为的监测和判断能力弱,本文研究一种基于嵌入式的电量计量采集系统。嵌入式电量计量系统的构成有两部分:高压侧用电信息无线监测装置和低压侧用电信息远程监测装置。高压侧用电信息无线监测装置的工作原理为对高压侧的电路信息进行采集,之后通过发射模块将信息传递至远程监控单元,监测人员可通过监控中心直接对电路信息进行远距离实时读取。低压侧用电信息远程监测装置对各个用电用户的用电信息进行直接识别,而后将识别分析结果输送到监控主站的信息库中。实验结果表明:高压无线检测装置检测到的数据通过换算后得到的用户用电情况曲线却不能和低压侧无线检测装置得到的数据曲线重合,说明该装置能够检测到人为窃电操作,验证了本文研究的嵌入式电量计量采集系统能够实现窃电的精确识别。 相似文献
17.
Wilkerson Chris Gao Hongliang Alameldeen Alaa R. Chishti Zeshan Khellah Muhammad Lu Shih-Lien 《Micro, IEEE》2009,29(1):96-103
Two proposed techniques let microprocessors operate at low voltages despite high memory-cell failure rates. They identify and disable defective portions of the cache at two granularities: individual words or pairs of bits. Both techniques use the entire cache during high-voltage operation while sacrificing cache capacity during low-voltage operation to reduce the minimum voltage below 500 mV. 相似文献
18.
Electrostatically driven gas valve with high conductance 总被引:2,自引:0,他引:2
Shikida M. Sato K. Tanaka S. Kawamura Y. Fujisaki Y. 《Journal of microelectromechanical systems》1994,3(2):76-80
The characteristics of a gas valve driven by electrostatic force are investigated. The gas valve consists of a pair of planar electrodes with a conductive film between them. Three valve ports pass through the electrode plates. The film is elastically bent in an S-shape in the middle and the S-bend moves back and forth as voltage is alternately applied between the film and each electrode. This valve has a high conductance achieved by large vertical film displacement. The valve is suitable for rarefied gas control systems, such as the molecular beam epitaxy (MBE) apparatus, which requires a gas flow rate on the order of 1 sccm under a low pressure of less than 100 Pa. Experimental models of the gas valve are constructed to investigate the valve's operation. The maximum pressure difference the valve can handle depends on the applied voltage and the size of the port orifice. A valve with 2.0 mm inlet and outlet ports can work under the operating condition of the MBE apparatus 相似文献
19.
针对数字式绝缘电阻测试仪的直流高压可控开关稳压电源和量程的自动切换电路,采用ARM 7结构的LPC2136芯片作为控制核心,在直流高压电源电路的反馈回路中控制直流高压输出值,在高压采集回路中实现量程切换。文中对直流高压电源的前向通道和反馈通道、高压采集回路中的量程切换电路的电路结构和基本原理进行了详细的阐述。设计将高压输出电压值的控制与量程切换控制在不同的电路中实现,提高了电路的可靠性,经测试达到了好的效果并得到应用。 相似文献
20.
High-current density DC magenetohydrodynamics micropump with bubble isolation and release system 总被引:1,自引:1,他引:0
One of the major challenges for integrated Lab-on-a-Chip (LOC) systems is the precise control of fluid flow in a micro-flow
cell. Magnetohydrodynamics (MHD) micropumps which contain no moving parts and capable of generating a continuous flow in any
ionic fluid offer an ideal solution for biological applications. MHD micropumping has been demonstrated by using both AC and
direct current (DC) currents by a number of researchers with varying degrees of success. However, current MHD designs based
on DC do not meet the flow rate requirements for fully automated LOC applications (>100 μl/min). In this research, we introduce
a novel DC-based MHD micropump which effectively increases flow rate by limiting the effects of electrolysis generated bubbles
at the electrode–electrolyte interface through isolation and a mechanism for their release. Gas bubbles, particularly, hydrogen
generated by high current density at the electrodes are the main culprit in low experimental flow rate compared with theoretical
values. These tiny bubbles coalesce in the flow channel thus obstructing the flow of fluid. Since hydrolysis is inevitable
with DC excitation, compartmentalized electrode channels with bubble isolating and coalescence retarding mechanisms and bubble
release systems are implemented to prevent the coalescence of these bubbles and minimize their effects on flow rate. In this
novel design called bubble isolation and release system, flow rate of up to 325 μl/min is achieved using 1 M NaCl solution
in DC mode with potentials of 5 V and current density of about 5,000 A/m2 for a main channel of 800 μm × 800 μm cross-section and 6.4 mm length. 相似文献