流体驱动智能电动控制仪用于PMMA微流控芯片电渗流的测量

采用自制的流体驱动智能电动控制仪作为电渗驱动控制源,结合电流跟踪法测量聚甲基丙烯酸甲酯(PMMA)芯片的电渗流,讨论了PMMA形成电渗的机理,给出了PMMA芯片通道电场强度与电渗速度的关系曲线。     

一种直接测定微流控芯片电渗流速度的新方法

随着微芯片技术的成熟,越来越迫切地需要有一个准确而简洁的电渗流速度的检测方法。根据荧光物质罗丹明123（Rh123）在不同pH缓冲溶液中迁移时间的变化,推导出Rh123在pH 9和10条件下分别有中性分子存在,而中性分子的移动速度等于电渗流速度,因此建立了直接以Rh123中性分子为标记物测定电渗流速度的方法。通过直接检测Rh123中性分子的迁移时间,计算得出所用玻璃微流控芯片在pH 9.3和pH 10.1的电渗流速度为3.9×10-4 cm2/(s·V)和4.1×10-4 cm2/(s·V),与经典方法对照无明显差异。     

微流体温度测量技术

综述了近年来应用于毛细管和微流控系统中的各种微流体测温技术,包括外部接触测温、依据液体物理参数变化测温、基于热敏物质测温、核磁共振和拉曼光谱测温以及基于激光的界面测温,并对各种测量方法的优缺点进行了讨论.     

微流控芯片中的流体驱动和控制方式

随着微流控芯片分析技术的发展,微流控芯片中的关键技术之一流体的驱动和控制技术逐步成为人们关注和研究的热点。本文主要综述了微流控芯片上的压力驱动、电驱动和其他驱动方式,着重介绍了电驱动方式,并讨论了各种驱动方式的优缺点以及发展前景。     

基于微流体脉冲驱动控制技术的电化学微流控芯片制备方法

基于微流体脉冲驱动控制技术搭建了电化学微流控芯片的制备系统.首先将纳米银墨水和甘油溶液分别微喷射到玻璃基底表面形成微电极图形和微流道液体阳模图形;然后分别进行烧结和聚二甲基硅氧烷(PDMS)模塑工艺制得微电极和微流道;最后将微电极和微流道键合形成电化学微流控芯片.研究了系统参量对液滴产生的影响以及液滴直径和重叠率对液滴成线的影响,制得的微电极最小线宽为45 μm、厚度为2.2 μm、电阻率为5.2 μΩ·cm,制得的微流道最小线宽为35 μm,流道表面光滑.采用制得的电化学微流控芯片进行了葡萄糖浓度的电化学流动检测.结果表明,葡萄糖溶液的浓度与响应电流具有较高的线性关系,可对一定浓度范围内的葡萄糖溶液进行定量检测.基于微流体脉冲驱动控制技术的电化学微流控芯片制备方法具有微喷射精度高、重复性好,制备系统结构简单、成本低廉等优点,可用于生化分析、生物传感器等领域的芯片制备.     

利用分叉微通道提高夹切进样微流控芯片电泳可靠性的探索

微流控芯片电泳在众多领域都有广阔的应用前景,但该技术的实际应用仍不多见,成功的微流控芯片电泳分析通常需要精确调控各储液池的液面高度、电极的位置等细节,对操作者的技术要求高。该研究在传统电泳芯片的进样通道和分离通道末端引入分叉结构,增加额外的储液池,利用液面差实现进样通道末端和分离通道末端溶液的持续更新,并以有机磷除草剂为模型分析物考察了设计的适用性。结果表明,在夹切进样条件下,利用该芯片可有效缩短连续多次进样分析时的进样时间,避免基线异常抬升,显著提高了分析结果的重现性。在选定的条件下,连续测定120次未发现分离性能的变化,峰高的相对标准偏差(RSD)可达0.56%。通过调整进样时间还可避免样品基体进入分离通道,简化分离谱图。     

微电渗流毛细管原位柱中流动相组成对电渗流的影响

采用原位聚合的方法合成了一种新型微电渗流毛细管电泳原位柱。考察了不同有机调节剂种类和浓度 ,pH对电渗流的影响 ,在 pH值 2 .3～ 9.8范围内 ,电渗流小于 19.6× 10 -10 m2 V-1s-1。当有机调节剂浓度从 6 0 %增加到 90 %时 ,电渗流仅从 6 .6× 10 -10 m2 V-1s-1增大到 4 8.9× 10 -10 m2 V-1s-1。结果表明 ,此类微电渗流柱在电色谱分离模式下电渗流保持在较低水平     

玻璃芯片上温控微阀的制备和微流体控制性能研究

聚N-异丙基丙烯酰胺(PNIPAAm)在临界温度(32 ℃)附近会发生敏锐的相变, 导致其体积和表面亲疏水性的突变. 利用这种由温度刺激引起的体积变化, 可以控制微通道内微流体的运动状态. 本文以2-羟基-2-甲基-1-苯基丙酮为引发剂, 水-乙醇混合体系为溶剂, 在玻璃芯片通道内局部区域以紫外光诱导聚合PNIPAAm整体柱塞, 制备温控微阀. 系统地考察了聚合条件对该阀的形态和性能的影响. 在此基础上, 建立了一个芯片上的集成化单温控阀流动注射分析模型, 利用镁离子与荧光探针O,O'-二羟基偶氮苯的螯合荧光反应, 表征温控微阀的控流效果. 结果表明, 所制作的微阀温控效果良好, 在微流控领域有应用前景.     

Electrochemistry of capillary systems with narrow pores. II. Electroosmosis

Manegold and Solf have reported systematic deviations of the electroosmotic properties of collodion membranes with narrow pores from predictions based on the Helmholtz–Smoluchowski model. To interpret the electroosmotic data quantitatively it is necessary to replace the assumption of the Helmholtz–Smoluchowski model that the thickness of the electric double layer is small compared with the pore radius by a new assumption. We have assumed that the counter ions are distributed homogeneously in the pore fluid. In Part I of this series of contributions, equations have been given describing the electroosmotic properties of a membrane with narrow pores based on the new assumption. These equations are derived here in detail and are applied to an analysis of the experimental data given by Manegold and Solf.     

Microvascular blood flow with heat transfer in a wavy channel having electroosmotic effects

The present paper addresses microvascular blood flow with heat and mass transfer in complex wavy microchannel modulated by electroosmosis. Investigation is carried out with joule heating and chemical reaction effects. Further, viscous dissipation is also considered. Using Debye–Huckel, lubrication theory, and long wavelength approximations, analytical solutions of dimensionless boundary value problems are obtained. The impacts of different parameters are examined for temperature and concentration profile. Furthermore, nature of pressure rise is also investigated to analyze the pumping characteristics. Important results of flow phenomena are explored by means of graphs.     

调控双电层电渗流数值研究

在通道壁面垂直施加一个调控电场可以改变双电层电荷密度和Zeta电位势,实现对电渗流的调控.采用电场Poisson方程、动量守恒的Navier-Stokes方程、电解质离子输运的Nernst-Planck方程和液体混合反应的组分浓度输运方程,本文对微通道壁面离散布置调控电极的情况进行了数值分析.数值算例包括单电极、双电极...     

Starting electroosmotic flow in an annulus and in a rectangular channel

The initial electroosmotic flow through a small pore or microchannel with annular or rectangular cross section is studied under the Debye-Hückel approximation. Analytical series solutions and their asymptotic behavior for small and large non-dimensional electrokinetic widths are found for these two basic cases. The explicit and accurate solutions are particularly useful for examining various geometric/physical effects on the transient time scales and the flow rates for the transient states. The steady flow rate of the smaller channel may be disproportionately smaller than a reference channel if the electric double layer is thick, but will be in close proportion to the area ratio if the electric double layer is thin. A smaller channel compared to a reference channel has a shorter transient time scale, and the transient flow has characters very different from the steady state if the electric double layer is thin. The total transient flow rate of several smaller pores or channels may exceed largely that of a single large pore or channel with the same total cross section on the transient time scale of the smaller channels. The results have important implications on liquid transport in micropores or channels by pulse voltages or more general time-varying voltages.     

Rapid concentration of deoxyribonucleic acid via Joule heating induced temperature gradient focusing in poly-dimethylsiloxane microfluidic channel

This paper reports rapid microfluidic electrokinetic concentration of deoxyribonucleic acid (DNA) with the Joule heating induced temperature gradient focusing (TGF) by using our proposed combined AC and DC electric field technique. A peak of 480-fold concentration enhancement of DNA sample is achieved within 40 s in a simple poly-dimethylsiloxane (PDMS) microfluidic channel of a sudden expansion in cross-section. Compared to a sole DC field, the introduction of an AC field can reduce DC field induced back-pressure and produce sufficient Joule heating effects, resulting in higher concentration enhancement. Within such microfluidic channel structure, negative charged DNA analytes can be concentrated at a location where the DNA electrophoretic motion is balanced with the bulk flow driven by DC electroosmosis under an appropriate temperature gradient field. A numerical model accounting for a combined AC and DC field and back-pressure driven flow effects is developed to describe the complex Joule heating induced TGF processes. The experimental observation of DNA concentration phenomena can be explained by the numerical model.     

芯片毛细管电泳管道中电渗流的数值模拟

利用芯片毛细管电泳管道中电渗流的数学模型,模拟了正常管道和细管道中十字交叉进样电渗流的性质以及其中样品浓度的分布.模拟的结果与文献报道一致.引人了时间参数,对电渗流以及浓度的分布作了一个含时的考察.同时,提出了通过管道表面修饰改变ζ电势的方法以消除弯道效应.     

The electroviscous effect in ethylcellulose latex suspensions. Effect of ionic strength and correlation between theory and experiments

 This article describes an experimental and theoretical investigation of the so-called primary electroviscous effect, i.e., the increase in suspension viscosity due to the existence of an electrical double layer around the particles. By measuring the viscosity of ethylcellulose latex suspensions, the electroviscous coefficient, the quantity measuring the effect, was estimated for different concentrations of 1-1 electrolyte in the dispersion medium. These data were compared with the predictions of Watterson and White's model, using the zeta potential of the particles deduced from electrophoretic mobility measurements. It was found that the theory considerably underestimates the effect. In an attempt to improve the agreement between data and predictions, the model was generalized to include the possibility (dynamic Stern layer) that ions in the inner part of the double layer have nonzero mobility. The general theory, however, predicts even lower values of the electroviscous coefficients, thus increasing the separation between calculated and measured electroviscous coefficients. A careful analysis of the ionic concentrations and velocity profiles with and without dynamic Stern layer corrections can account for this fact, but leaves unsolved the problem of the large discrepancies found in the theoretical explanation of the strength of the electroviscous effect. Received: 19 October 1999/Accepted: 17 December 1999     

Recent Advanced Applications of Ionic Liquid for Future Iontronics

Recently, electronic devices that make use of a state called the electric double layers (EDL) of ion have opened up a wide range of research opportunities, from novel physical phenomena in solid-state materials to next-generation low-power consumption devices. They are considered to be the future iontronics devices. EDLs behave as nanogap capacitors, resulting the high density of charge carriers is induced at semiconductor/electrolyte by applying only a few volts of the bias voltage. This enables the low-power operation of electronic devices as well as new functional devices. Furthermore, by controlling the motion of ions, ions can be used as semi-permanent charge to form electrets. In this article, we are going to introduce the recent advanced application of iontronics devices as well as energy harvesters making use of ion-based electrets, leading to the future iontronics research.     

#电渗泵流动注射系统测定水中氟

对电渗泵的原理及其在流动注射系统中的应用特点作了详细讨论，并用氟试剂分光光度法测定了自来水中氟化物含量。     

Influence of the three-dimensional heterogeneous roughness on electrokinetic transport in microchannels

Surface roughness has been considered as a passive means of enhancing species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of three-dimensional (3D) roughness and surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. We consider that all 3D prismatic rough elements have the same surface charge or zeta potential, the substrate (the microchannel wall) surface has a different zeta potential. The results showed that the rough channel's geometry and the electroosmotic mobility ratio of the roughness elements' surface to that of the substrate, epsilon(mu), have a dramatic influence on the induced-pressure field, the electroosmotic flow patterns, and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample-species transport presents a tidal-wave-like concentration field at the intersection between four neighboring rough elements under low epsilon(mu) values and has a concentration field similar to that of the smooth channels under high epsilon(mu) values.