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.     

海水中稳恒电流电场的点电极计算模型

根据点电极基本假设，利用均匀介质中稳恒电流场与静电场的相似性，分别采用分离变量法和镜像法计算了点电极稳恒电流场在空气-海水-海床三层介质平行界面模型下的电位分布。从而得到了海水中稳恒电流电场的计算模型．计算结果表明：点电极的电场分布具有明显的特征，可作为舰船电场电极阵列模拟的计算单元。     

基于低雷诺数理论的电泳芯片微管道电渗流仿真

电泳芯片作为典型的低雷诺数、低体积流速的微流体器件,电渗流作为非常重要的物理现象,其大小直接影响分离情况和分析结果的精密度和准确度.基于低雷诺数理论建立电泳芯片微管道内电渗流的数学模型,利用有限差分法进行求解.当德拜长度为5nm时,不同Zeta电势下下,微管道内电渗流的流动情况为塞状流,电渗流的最大速度随着Zeta电势的增加而线性增加;当Zeta电势为-100mV,不同德拜长度下,电渗势沿壁面的法线方向呈指数级衰减.在不同的德拜长度下,电渗流的速度分布几乎一样,且当德拜长度改变时,电渗流的最大速度不变.     

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.     

PDMS微流控芯片微筛阵列流场的Micro-PIV分析

针对微流控芯片上的细胞培养技术,很多微流控芯片设计力图追求高通量,但并未考虑芯片中流场的分布状态,导致细胞培养效果不佳.本文介绍了直径1μm的荧光粒子以30μL/min的速度注入芯片中,利用Micro-PIV技术对设计的含有16μm微筛阵列的PDMS微流控芯片进行流场、流速的测试与分析,得到高分辨率的流场、速度矢量分布图,并且与ANSYS软件模拟结果进行比较.实验结果表明:液体经过微筛阵列时,流速逐渐减小,流场分布稳定均一,模拟结果与实际结果吻合.     

高效jurkat细胞富集芯片的制备与性能研究

利用微机电加工工艺在硅基上制备介电电泳叉指式阵列微电极,对jurkat白血病细胞进行富集实验研究,得出高效富集参数。当施加电压为5Vp-p,频率为700k Hz的正弦交流信号时,白血病细胞富集效率高达96.43%。在此基础上,结合介电电泳受力原理,利用有限元分析软件对介电电泳芯片模型进行电场仿真分析,得出富集现象为白血病细胞受负向介电电泳力下的高效富集。     

硅基电泳芯片非接触电导检测器

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二电极非接触电导检测器.讨论了影响电导检测响应灵敏度的相关因素;采用MEMS分析软件及等效电路模拟仿真,确定了检测器的相关参数,电极长度为550μm,宽度为15μm,间距为80μm,绝缘层厚度为1μm,电导检测工作频率为300 kHz.在加工技术中,选用SOI(sili-con on insulator)基片制作十字形微沟道及集成电导检测电极,采用深刻蚀和隔离技术使检测电极被完全隔离成孤岛,利用硼掺杂技术在分离沟道末端侧壁形成立体电极,获得了集成非接触电导检测电极的硅基电泳芯片.在外加Vpp为10 V、工作频率为300 kHz的正弦波激励下,进行了Na+无机阳离子浓度梯度实验以及Na+和Li+混合无机阳离子的电泳分离检测.结果表明,Na+浓度在1×10-9～1×10-4 mol/L范围内,电导响应信号随着离子浓度的增加而增大,检出限达到1×10-9 mol/L;Na+和Li+混合无机阳离子的分离度达到2.0,实现基线分离.     

大面积VHF-PECVD反应室喷淋式平板电极间电场和流场数值模拟

以大面积喷淋式平板电极甚高频等离子体增强化学气相沉积(VHF-PECVD)反应室为研究对象,利用FlexPDE和CFD-ACE+商业软件,对反应室电极间的电场和流场分布进行了数值模拟。根据数值模拟结果可知:对于大面积喷淋式平板电极VHF-PECVD反应室,电极间气体流速分布呈现管流特征,而气压分布和电场分布具有类似的分布规律,即在大面积电极中央区域电场较强气压较高,而电极边缘区域电场较弱气压较低;另外,反应室采用喷淋式平板电极进行反应气体馈入,气体总流量、工作气压和电极间距是调节电极间气压分布均匀性的重要参量,采用大电极间距、高工作气压,以及小的气体总流量有助于获得均匀的气压分布。     

电流密度对微/纳结构电铸成型模芯质量的影响

利用多物理场耦合分析软件COMSOL Multiphysics,模拟微/纳结构电铸过程中阴极表面的电场分布,研究不同电流密度下微/纳结构表面的电场分布及电铸层生长前沿情况。仿真结果表明:采用较低的初始电流密度,可有效改善微/纳结构生长前沿铸层厚度的均匀性。选用纳米光阑和纳米柱阵列2种微/纳结构母板进行电铸实验,将初始电流密度从4A/dm2调至1A/dm2,纳米光阑母板成型最大误差60nm降至±20nm之内。通过合理设置初始电流密度、增强阴极表面溶液流动强度等措施,纳米柱阵列模芯特征直径尺寸误差由6.27%下降至2.49%,有效提高电铸模芯的复制质量。     

表面贴附微透镜阵列的OLED诱导荧光检测系统

为进一步减小光源的体积、简化光路系统结构，消除毛细管电泳芯片诱导荧光检测系统中激发光源的反射光和杂散光的干扰，设计并建立了垂直层叠结构的有机发光二极管诱导荧光检测系统。针对有机发光二极管器件发光强度较低的问题，采用在器件的玻璃基底表面贴附微透镜阵列薄膜的方法，提高了入射光的强度。在对CCD积分时间、PDMS微透镜直径及两偏振片间的偏振角度等参数进行优化之后，利用检测系统实现了罗丹明B样品溶液的毛细管电泳分离。     

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.     

电泳芯片的低电压分离模型及讨论

电泳芯片是一种重要的微型分析仪器。针对目前电泳芯片分离电压高、不利于一体化集成等问题,利用在分离通道上分段、交替、循环施加电压的方法,提出电泳芯片的一种低电压分离模型,以降低电泳芯片的分离电压。同时,对影响电压降低的相关因素进行了详细的讨论,为这种低电压电泳芯片的设计提供了一定的理论基础。     

Numeric simulation of heat transfer and electrokinetic flow in an electroosmosis-based continuous flow PCR chip

Precise design and operational control of the polymerase chain reaction process is key to the performance of on-chip DNA analysis. This research is dedicated to understanding the fluid flow and heat transfer mechanisms occurring in continuous flow PCR chips from the engineering point of view. In this work, a 3-dimensional model was developed to simulate the electrical potential field, the flow field, and the temperature field in an electroosmosis-based continuous flow PCR chip. On the basis of the simultaneous solution to this model, the effects of the channel/chip size, the chip material, and the applied voltage difference on the temperature distribution and control are discussed in detail. The importance of each heat transfer mechanism for different situations is also discussed. It was found that if a larger chip thickness or a material with a lower heat conductivity was used, the temperature in the microfluidic PCR chip would decrease dramatically. The effects of the applied electrical field strength and flow velocity on the temperature distribution, however, are negligible for microchannels with a small cross-sectional area. With bigger channels, the flow direction will affect the temperature distribution in the channel because heat convection will dominate heat transfer.     

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.     

Electroosmotically induced hydraulic pumping with integrated electrodes on microfluidic devices

Electroosmotic manipulation of fluids was demonstrated using thin metal electrodes integrated within microfluidic channels at the substrate and cover plate interface. Devices were fabricated by photolithographically patterning electrodes on glass cover plates that were then bonded to polymeric substrates into which the channels were cast. Polymeric substrates were used to provide a permeable membrane for the transport and removal of gaseous electrolysis products generated at the electrodes. Electroosmotic flow between interdigitated electrodes was demonstrated and provided electric field-free pumping of fluids in sections of the channel outside of the electrode pairs. The resultant pumping velocities were shown to be dependent on the applied voltage, not on the applied field strength, and independent of the length of the electroosmotically pumped region.     

Isoelectric focusing in a microfluidically defined electrophoresis channel

A new form of microchip isoelectric focusing that allows efficient coupling with pretreatment processes is reported. The sample is conveyed in a carrier ampholyte solution to the separation channel that is connected at both ends by two V-shaped lead channels, which supply electrode solutions to the connection point and complete the electrical connection to off-chip electrodes. The relatively high electric conductivity of the electrode solutions compared with that of the pH gradient enables focusing with a 2% loss of applied voltage at the electrodes using the lead channels. A glass microchip was constructed specifically for this configuration. The channel wall was coated with polydimethylacrylamide, and the IEF chip was operated in a chip holder equipped with on-chip connector valves. A plug of fluorescence-labeled peptide p I markers with p I values ranging from 3.64 to 9.56 with carrier ampholyte solution (pH 3-10) was introduced into the separation channel. When the plug reached the channel segment (24 mm in length) between the connection points with the electrolyte lead channels, isoelectric focusing was started after filling the lead channels with electrolyte solutions. The peptide markers were observed using scanning fluorescence detection. The entire range of the pH gradient was established in the segment after approximately 2 min. Isoelectric focusing of three consecutively injected sample plugs containing different p I markers was demonstrated.     

High-throughput microfabricated CE/ESI-MS: automated sampling from a microwell plate

A new design for high-throughput microfabricated capillary electrophoresis/electrospray mass spectrometry (CE/ ESI-MS) with automated sampling from a microwell plate is presented. The approach combines a sample-loading port, a separation channel, and a liquid junction, the latter for coupling the device to the MS with a miniaturized subatmospheric electrospray interface. The microdevice was attached to a polycarbonate manifold with external electrode reservoirs equipped for electrokinetic and pressure-fluid control. A computer-activated electropneumatic distributor was used for both sample loading from the microwell plate and washing of channels after each run. Removal of the electrodes and sample reservoirs from the microdevice structure significantly simplified the chip design and eliminated the need both for drilling access holes and for sample/buffer reservoirs. The external manifold also allowed the use of relatively large reservoirs that are necessary for extended time operation of the system. Initial results using this microfabricated system for the automated CE/ESI-MS analysis of peptides and protein digests are presented.     

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.     

On-chip high-speed sorting of micron-sized particles for high-throughput analysis

A new design of particle sorting chip is presented. The device employs a dielectrophoretic gate that deflects particles into one of two microfluidic channels at high speed. The device operates by focussing particles into the central streamline of the main flow channel using dielectrophoretic focussing. At the sorting junction (T- or Y-junction) two sets of electrodes produce a small dielectrophoretic force that pushes the particle into one or other of the outlet channels, where they are carried under the pressure-driven fluid flow to the outlet. For a 40 microm wide and high channel, it is shown that 6 microm diameter particles can be deflected at a rate of 300/s. The principle of a fully automated sorting device is demonstrated by separating fluorescent from non-fluorescent latex beads.     

Using channel depth to isolate and control flow in a micro free-flow electrophoresis device

A multiple-depth micro free-flow electrophoresis chip (mu-FFE) has been fabricated with a 20-microm-deep separation channel and 78-microm-deep electrode channels. Due to the difference in channel heights, the linear velocity of buffer in the electrode channels is approximately 15 times that of the buffer in the separation channel. Previous mu-FFE devices have been limited by electrolysis product formation at the electrodes. These electrolysis products, manifested as bubbles, decreased the electric field and disrupted the buffer flow profile, limiting performance and preventing continuous operation. Using channel depth to control buffer flow over the electrodes and in the separation channel effectively removes electrolysis products, allowing continuous operation. The linear velocities in the channels were confirmed using particle velocimetry and compared well with values predicted using lubrication theory. A separation potential of 645 V could be applied before significant Joule heating was observed. This corresponded to an electric field of 586 V/cm in the separation channel, a 4-fold increase over our previous design. A separation of fluorescent standards was demonstrated using the new mu-FFE device. Resolution increased by a factor of 1.3 over our previous design, even when operated under similar conditions, suggesting that effective removal of electrolysis products is more important than originally thought.