低电压电泳芯片及其在生化样品分析中的应用

为了解决微流控电泳芯片集成化问题,设计并制作出一种具有管道两侧微阵列电极结构的硅-PDMS复合低电压电泳芯片.通过电路控制程序在微侧壁阵列电极上施加交替循环的低电压,以实现芯片微管道中低电压电泳过程;并对硅-PDMS芯片的电绝缘性、伏安曲线及电渗流等性能进行了测试和评价.以pH为10.0、10mmol/L的硼砂作为缓冲体系,分离场强150V/cm、切换时间3s的条件下,完成了10-4mol/L的苯丙氨酸和精氨酸的低电压电泳分离,分离度达1.6,实现了两种氨基酸的完全分离.在此基础上,将系统用于牛血清白蛋白和α-乳白蛋白的分离,并初步实现了该两种蛋白质的芯片电泳分离.     

电泳芯片上低工作电压分离模式的电场模拟分析

本文根据电泳芯片的低工作电压分离理论模型,选定采用对分离管道侧壁阵列电极以等间距施加电压的方式作为电场模拟分析的模型。利用ANSYS有限元软件分析系统,对微分离管道中的电场分布进行模拟仿真分析。重点探讨了阵列电极的布置方式、电极个数和位置、微分离管道形状、电极表面绝缘层等因素对微管道中电场分布的影响;详细计算和优化了利用电极阵列实现低工作电压分离过程中,分离微管道及电极阵列的基本设计和结构参数。这为研制一种微型化的低电压电泳芯片系统奠定了一定的理论基础。     

芯片毛细管电泳技术的应用与进展

介绍了目前芯片毛细管电泳的主要分离技术:芯片毛细管区带电泳、芯片毛细管凝胶电泳、芯片胶束电动色谱、芯片毛细管电色谱及多相层流无膜扩散分离.芯片毛细管电泳的研究已经取得了很大的进展,研制出了多种微型化、集成化的芯片,多种分离技术在芯片上的开发应用,显示出芯片毛细管电泳技术在众多分析领域会有广阔的发展前景.     

焦耳热对芯片电泳分离效率影响的模拟分析和实验

采用CoventorWare有限元分析软件对电泳芯片管道内焦耳热效应进行了模拟计算和分析,以牛血清白蛋白和溶菌酶作为样品分析对象,通过考虑芯片不同绝缘层厚度、分离场强、缓冲液浓度条件下分离效能,来考察芯片电泳过程中管内焦耳热现象对样品分离的影响,明确了在综合电泳分离条件中限制焦耳热的必要性.     

高磁场强度的矩形平面磁控溅射靶的设计

研究利用高磁场强度实现低电压磁控溅射的可能性;通过理论分析、实际设计和实验,分析了限制矩形平面磁控溅射靶表面水平磁场强度B的上限的几个因素;设计出了B为0.09T的矩形平面磁控溅射靶。结果表明:B的增加显著降低了磁控溅射镀膜工艺的着火电压和维持放电电压,为实现低电压磁控溅射提供了另一种思路。     

毛细管电泳非接触电导检测器的研制

非接触电导检测法已经成为毛细管电泳芯片中一种通用的物质分离检测方法．本文提出了一种微型化的电容耦合非接触电导分析系统,采用新颖的三明治电极结构减小了电极之间的寄生电容．这种电极结构能够有效地减小电极的长度,克服了非接触电导检测中电极易于折断的缺点．当采用电极宽度1mm、电极间距1mm、MES／His缓冲溶液浓度为20mmol／L和激励电压20Vpp、90kHz的条件时,检测器具有最好的分离效果．在最佳的分离效果,实现了1mmol／L的K^＋和Mg^2＋混合无机阳离子的分离检测．     

电泳芯片系统的研制和应用

叙述了电泳芯片的设计和制作，并详细阐述了电泳芯片的进样方法，电泳操作方法等。实验结果表明，本系统能对DNA片段进行很好的分离和检测，检测极限已达到10^-19mol。     

基于SU8和PMMA的毛细管电泳芯片制作

提出了一种简易的基于SU8和PMMA的电泳芯片的制作方法,研究了PMMA基底上SU8胶微管道的光刻和薄膜微电极的lift-off制作工艺,探讨了PMMA材料特性对薄膜微电极和SU8胶光刻的影响,通过热压方法完成芯片的键合封装,实现了一种快速、高质量的电泳芯片制作工艺,同时与电泳芯片的UV-LIGA工艺具有很好的兼容性.     

低电压压缩机应用于空调系统的试验研究

本文针对很多农村地区,在夏季制冷季节供电电压偏低的问题,设计了一款在低电压时仍能够正常运行的空调器;通过试验验证,采用主绕组电阻可变的抽头压缩机最低运行电压可以降低到150 V左右,基本满足农村低电压地区空调器的使用。     

关于微型自由流动电泳芯片设计方法的研究

自由流动电泳(FFE)技术是对流经平面流道的连续流动的分析物进行电泳分离。主要探讨多种对芯片设计的改善,进而减少电解气泡的影响,提高分离效率,对了解微型自由流动电泳芯片有一定的参考意义。     

Contactless conductivity detector for microchip capillary electrophoresis

A microfabricated electrophoresis chip with an integrated contactless conductivity detection system is described. The new contactless conductivity microchip detector is based on placing two planar sensing aluminum film electrodes on the outer side of a poly(methyl methacrylate) (PMMA) microchip (without contacting the solution) and measuring the impedance of the solution in the separation channel. The contactless route obviates problems (e.g., fouling, unwanted reactions) associated with the electrode-solution contact, offers isolation of the detection system from high separation fields, does not compromise the separation efficiency, and greatly simplifies the detector fabrication. Relevant experimental variables, such as the frequency and amplitude of the applied ac voltage or the separation voltage, were examined and optimized. The detector performance was illustrated by the separation of potassium, sodium, barium, and lithium cations and the chloride, sulfate, fluoride, acetate, and phosphate anions. The response was linear (over the 20 microM-7 mM range) and reproducible (RSD = 3.4-4.9%; n = 10), with detection limits of 2.8 and 6.4 microM (for potassium and chloride, respectively). The advantages associated with the contactless conductivity detection, along with the low cost of the integrated PMMA chip/detection system, should enhance the power and scope of microfluidic analytical devices.     

Capillary electrophoresis microchips for separation and detection of organophosphate nerve agents

A miniaturized analytical system for separating and detecting toxic organophosphate nerve agent compounds, based on the coupling of a micromachined capillary electrophoresis chip with a thick-film amperometric detector, is described. Factors influencing the on-chip separation and detection processes have been optimized. Using a MES buffer (20 mM, pH 5.0) running buffer, a 72-mm-long separation channel, and a separation voltage of 2000 V, baseline resolution is observed for paraoxon, methyl parathion, fenitrothion, and ethyl parathion in 140 s. Such miniaturization and speed advantages are coupled to submicromolar detection limits and good precision. Applicability to spiked river water samples is demonstrated, and the implications for on-site environmental monitoring and rapid security screening/warning are discussed.     

侧壁四电极电容耦合非接触电导检测器(英文)

研制了一种集成于硅基电泳芯片分离沟道末端侧壁的新型四电极电容耦合非接触电导检测器.研究了该电导检测器的等效模型,对等效电路模型中的参数进行了公式推导,并讨论了影响电导检测响应灵敏度的相关因素.采用深刻蚀及离子注入加工技术制得了用于电导检测的立体电极.制作了基于锁相放大原理的信号处理电路,对该电导检测的频率响应及灵敏度进行了测试分析.实验结果表明,当激励信号频率为300 kHz时,该电导检测器具有最佳线性度;不同浓度Na+溶液响应电压差值为5 mV;检测限达到10-8mol/L;且成功实现了Na+和Li+混合无机阳离子的电泳分离在线检测.     

High-speed free-flow electrophoresis on chip

A microfluidic device has been developed for continuous separation in free-flow electrophoresis (FFE) mode. A mixture of two fluorescent reagents is separated into two component streams in 75 ms using a sample flow rate of 2 nL/s. The residence time of sample in the whole separation compartment is 2 s. The separation bed volume is 0.2 microL. The chip has also been used for free-flow electrophoresis of fluorescein-5-isothiocyanate-labeled amino acids in both aqueous and binary media. The short residence time and small sample flow rate make the FFE chip feasible for on-line monitoring on production lines and other chemical or biochemical processes. The in-house-made chip was composed of a plain glass substrate of 1.5-mm thickness and a PDMS layer of 0.3-mm thickness with micromachined channels. The channel design presented in this paper is versatile. With the same kind of PDMS substrates, chips for various purposes can be made depending on the locations of the reservoirs, which are cut out on the PDMS substrate. The results presented verify the scaling laws and allow prediction of FFE performances comparable to what is now state of the art on capillary electrophoresis chips.     

Improving the compatibility of contact conductivity detection with microchip electrophoresis using a bubble cell

A new approach for improving the compatibility between contact conductivity detection and microchip electrophoresis was developed. Contact conductivity has traditionally been limited by the interaction of the separation voltage with the detection electrodes because the applied field creates a voltage difference between the electrodes, leading to unwanted electrochemical reactions. To minimize the voltage drop between the conductivity electrodes and therefore improve compatibility, a novel bubble cell detection zone was designed. The bubble cell permitted higher separation field strengths (600 V/cm) and reduced background noise by minimizing unwanted electrochemical reactions. The impact of the bubble cell on separation efficiency was measured by imaging fluorescein during electrophoresis. A bubble cell four times as wide as the separation channel led to a decrease of only 3% in separation efficiency at the point of detection. Increasing the bubble cell width caused larger decreases in separation efficiency, and a 4-fold expansion provided the best compromise between loss of separation efficiency and maintaining higher field strengths. A commercial chromatography conductivity detector (Dionex CD20) was used to evaluate the performance of contact conductivity detection with the bubble cell. Mass detection limits (S/N = 3) were as low as 89 +/- 9 amol, providing concentration detection limits as low as 71 +/- 7 nM with gated injection. The linear range was measured to be greater than 2 orders of magnitude, from 1.3 to 600 microM for sulfamate. The bubble cell improves the compatibility and applicability of contact conductivity detection in microchip electrophoresis, and similar designs may have broader application in electrochemical detection as the expanded detection zone provides increased electrode surface area and reduced analyte velocity in addition to the reduction of separation field effects.     

Microfabricated capillary electrophoresis amino acid chirality analyzer for extraterrestrial exploration.

Chiral separations of fluorescein isothiocyanate-labeled amino acids have been performed on a microfabricated capillary electrophoresis chip to explore the feasibility of using such devices to analyze for extinct or extant life signs in extraterrestrial environments. The test system consists of a folded electrophoresis channel (19.0 cm long x 150 microns wide x 20 microns deep) that was photolithographically fabricated in a 10-cm-diameter glass wafer sandwich, coupled to a laser-excited confocal fluorescence detection apparatus providing subattomole sensitivity. Using a sodium dodecyl sulfate/gamma-cyclodextrin pH 10.0 carbonate electrophoresis buffer and a separation voltage of 550 V/cm at 10 degrees C, baseline resolution was observed for Val, Ala, Glu, and Asp enantiomers and Gly in only 4 min. Enantiomeric ratios were determined for amino acids extracted from the Murchison meteorite, and these values closely matched values determined by HPLC. These results demonstrate the feasibility of using microfabricated lab-on-a-chip systems to analyze extraterrestrial samples for amino acids.     

Elimination of high-voltage field effects in end column electrochemical detection in capillary electrophoresis by use of on-chip microband electrodes

The influence of the separation voltage on end column electrochemical detection (EC) in capillary electrophoresis (CE) has been investigated using an electrochemical detector chip based on an array of microband electrodes. It is shown, both theoretically and experimentally, that the effect of the CE electric field on the detection can be practically eliminated, without using a decoupler, by positioning the reference electrode sufficiently close to the working electrode. In the present study, this was demonstrated by using an experimental setup in which neighboring microband electrodes on a chip, positioned 30 microns from the end of the CE capillary, were used as working and reference electrodes, respectively. The short distance (i.e., 10 microns) between the working and reference electrode ensured that both of the electrodes were very similarly affected by the presence of the CE electric field. With this experimental setup, no significant influence of the CE voltage on the peak potentials for gold oxide reduction could be seen for CE voltages up to +30 kV. The detector noise level was also found to be reduced.     

Integrated preconcentration SDS-PAGE of proteins in microchips using photopatterned cross-linked polyacrylamide gels

The potential of integration of functions in microfluidic chips is demonstrated by implementing on-chip preconcentration of proteins prior to on-chip protein sizing by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two polymeric elements-a thin (approximately 50 microm) size exclusion membrane for preconcentration and a longer (approximately cm) porous monolith for protein sizing-were fabricated in situ using photopolymerization. Contiguous placement of the two polymeric elements in the channels of a microchip enabled simple and zero dead volume integration of the preconcentration with SDS-PAGE. The size exclusion membrane was polymerized in the injection channel using a shaped laser beam, and the sizing monolith was cast by photolithography using a mask and UV lamp. Proteins injected electrophoretically were trapped on the upstream side of the size exclusion membrane (MW cutoff approximately 10 kDa) and eluted off the membrane by reversing the electric field. Subsequently, the concentrated proteins were separated in a cross-linked polyacrylamide monolith that was patterned contiguous to the size exclusion membrane. The extent of protein preconcentration is easily tuned by varying the voltage during injection or by controlling the sample volume loaded. Electric fields applied across the nanoporous membrane resulted in a concentration polarization effect evidenced by decreasing current over time and irreproducible migration of proteins during sizing. To minimize the concentration polarization effect, sieving gels were polymerized only on the separation side of the membrane, and an alternate electrical current path was employed, bypassing the membrane, for most of the elution and separation steps. Electrophoretically sweeping a fixed sample volume against the membrane yields preconcentration factors that are independent of protein mobility. The volume sweeping method also avoids biased protein loading from concentration polarization and sample matrix variations. Mobilities of the concentrated proteins were log-linear with respect to molecular weight, demonstrating the suitability of this approach for protein sizing. Proteins were concentrated rapidly (<5 min) over 1000-fold followed by high-resolution separation in the sieving monolith. Proteins with concentrations as low as 50 fM were detectable with 30 min of preconcentration time. The integrated preconcentration-sizing approach facilitates analysis of low-abundant proteins that cannot be otherwise detected. Moreover, the integrated preconcentration-analysis approach employing in situ formation of photopatterned polymeric elements provides a generic, inexpensive, and versatile method to integrate functions at chip level and can be extended to lowering of detection limits for other applications such as DNA analysis and clinical diagnostics.     

A high-throughput continuous sample introduction interface for microfluidic chip-based capillary electrophoresis systems

The development of efficient sample introduction and pretreatment systems for microfluidic chip-based analytical systems is important for their application to real-life samples. In this work, world-to-chip interfacing was achieved by a novel flow-through sampling reservoir featuring a guided overflow design. The flow-through reservoir was fabricated on a 30 x 60 x 3 mm planar glass chip of crossed-channel design used for capillary electrophoresis separations. The 20-microL sample reservoir was produced from a section of plastic pipet tip and fixed at one end of the sampling channel. Sample change was performed by pumping 80-microL samples sandwiched between air segments at approximately 0.48 mL/min flow rate through the flow-through reservoir, introduced from an access hole on the bottom side of the chip. A filter paper collar wrapped tightly around the reservoir guided the overflowing sample solution into a plastic trough surrounding the reservoir and then to waste. The performance of the system was demonstrated in the separation and determination of FITC-labeled arginine, glycine, phenylalanine, and glutamic acid with LIF detection, by continuously introducing a train of different samples through the system without electrical interruption. Employing a separation channel of 4 cm (2-cm effective separation length) and 1.4-kV separation voltage, maximum throughputs of 80/h were achieved with <4.1% carryover and precisions ranging from 1.5% for arginine to 2.6% RSD (n = 11) for glycine. The sampling system was tested in the continuous monitoring of the derivatizing process of amino acids by FITC over a period of 4 h, involving 166 analytical cycles. An outstanding overall precision of 4.8% RSD (n = 166) was achieved for the fluorescein internal standard.