声表面波实现微流体垂向输运

提出了声表面波实现微流体垂向输运方法,使得纸基微流器件具有前处理操作功能.在128°旋转Y切割X传播方向的LiNbO3基片上光刻叉指换能器对和反射栅,纸基微流器件通过贴合于压电基片表面的PDMS置放于距压电基片上方2mm处,经功率放大器放大的RF信号加到叉指换能器对上,激发的两相声表面波使得压电基片上待分析微流体垂向运...     

微系统科技的发展及电化学的新应用

本文根据田昭武在中国化学会第一届全国纳米技术与应用会议 (2 0 0 0 .11.2 8,厦门 )特邀大会报告内容整理而成 :1　微系统技术概述 (技术的必要性和前景 )2　发展微系统技术的特殊困难3　电化学在微系统技术中的应用　 3.1　用于复杂 3D 图形微加工的约束刻蚀剂层技术 (CELT)　 3.2　聚焦电泳和微系统在 (生物 )化学中的应用 (μ TAS或芯片上实验室 )　 3.3　芯片实验室中微流体输运网络的合理选择之一 -灵巧 (Smart)电渗泵4　结论     

基于激光加工的聚合物微通道的流动特性研究

对高斯形截面的微通道中的流场进行了数值分析.结果表明,在压力驱动下,对于深宽比<3的通道,存在2个流速极值,此时通道的顶部对流体的输送也具有较大的贡献.对于深宽比>3的通道却只存在一个极值,此时顶部对流体输送几乎不起作用.研究结果对微通道中流体的流动特性研究具有指导意义.     

具有串/并联复合离子输运特性的仿生纳米通道的构筑与整流性能

人工构筑了基于分枝氧化铝纳米通道的串/并联复合的纳流体二极管体系, 其具有可调的离子整流性能. 在这种两级分枝结构的1-2-2, 1-2-3, 1-3-2和1-3-3型氧化铝纳米通道中, 若将每一个分枝节点等效为一个二极管, 那么其一级分枝节点相当于串联的1个二极管, 二级分枝节点相当于并联的多个二极管. 因此1-2-2和1-2-3型纳米通道的电路图可等效为并联的2个二极管与第3个二极管相串联, 1-3-2和1-3-3型纳米通道的电路图可等效为并联的3个二极管与第4个二极管相串联. 但由于1-2-2和1-2-3型以及1-3-2和1-3-3型的二级分枝的结构和数目不同, 可将这4种纳米通道等效为不同的串/并联复合特性的纳流体二极管体系, 并且表现出依次增大的离子整流. 即分枝氧化铝纳米通道内部一级分枝和二级分枝的结构或数目共同调控的表面电荷非对称性可以改变其离子整流性能. 进一步地, 具有代表性的1-2-2型分枝纳米通道的整流率随分枝通道长度的增加而增加, 这表明分枝部分对整个串/并联复合纳流体二极管的整流特性起到决定性的作用. 相比于以前的单个离子二极管体系, 这种具有串/并联复合特性的多级分枝氧化铝纳米通道将为构筑更复杂的仿生纳流体二极管的研究提供有价值的借鉴.     

分子电子学的新进展

分子尺度电子学通过构筑基于微尺度电极和单个分子或者少量分子聚集体的"电极-分子-电极"结，研究跨越分子的电荷输运性质.它将分子本征化学特性与器件构筑相结合，考察分子的理化特性与电荷输运的构效关系，揭示微尺度的量子输运动力学原理，并探索基于分子的功能电子器件.是一个集化学、物理学与微电子学为一体的交叉学科.总结整理了分子电子学近些年在器件制备、输运机理及应用方面部分有代表性的进展.     

微流体芯片动态调控蛋白水溶液pH或Ca~(2+)浓度

模拟蚕和蜘蛛的纺丝系统,以载玻片(75×25mm)为基片,SU-8为阳模材料,聚二甲基硅氧烷(PDMS)为微通道(宽500μm,深100μm)构筑材料,利用光刻及模塑成型等技术设计、制备了微流体芯片,并应用于再生丝素蛋白(RSF)水溶液组成的动态调控。该芯片利用微流体的层流特性使RSF水溶液与pH缓冲液或钙离子缓冲液在微通道内平行流动而不发生混合。在水溶液中RSF质量分数不变的前提下,通过离子扩散实现了流动场下RSF水溶液pH值或钙离子浓度的动态调控。     

CO2激光直写加工聚合物微流体芯片的建模研究

在CO2激光直写聚合物(PMMA)微流体芯片加工原理基础上,对激光直写PMMA微流道的数学模型进行了研究.采用能量守恒原理对激光直写PMMA微流道成型进行分析,结果表明,其微流道的形状呈高斯函数型分布,并获得了微流道深度和激光功率、加工速度的函数关系及微流道截面形状的数学模型.实验数据较好地验证了所建模型的正确性,该模型对CO2激光直写聚合物(PMMA)微流体芯片的加工工艺具有很好的指导作用.     

直接甲酸钠/铁氰化钾微流体燃料电池性能研究

微流体燃料电池(MFC)利用两股流体在微通道内呈平行层流的特性, 无需传统燃料电池中的质子交换膜, 自动将燃料与氧化剂隔开. 本工作构建了阴阳极均为碱性介质且阴极无催化剂即可反应的直接甲酸钠/铁氰化钾MFC, 考察了反应物流速、氧化剂浓度、燃料浓度对该电池产电性能的影响. 实验结果表明, 在反应物流速为200 μL•min^-1, 铁氰化钾氧化剂浓度为1 mol•L^-1, 甲酸钠燃料浓度为1.5 mol•L^-1时, 该微流体燃料电池性能达到最优, 其最高功率密度为123.93 mW•cm^-2, 极限电流密度为220.93 mA•cm^-2. 为了获得该电池的稳定运行性能, 对电池进行了恒电压放电实验. 结果表明, 该电池在2.25 h内可以持续较稳定地放电. 此外, 对该电池在开路状态下进行了电化学阻抗谱测试, 获得该电池内阻为18.4 Ω.     

多靶标生物标志物检测的微流体磁敏生物传感器研制

将磁敏传感器与微流体测试卡集成,研制了可快速检测多靶标生物标志物的微流体免疫磁敏传感器。以3种消化系统肿瘤标志物(甲胎蛋白、癌胚抗原、糖链抗原)为模型靶标,对免疫反应各步反应的液体流速、免疫反应时间以及反应后的冲洗速度进行了优化,评价了多靶标同时检测的系统性能。在微流体磁敏生物传感器系统中,建立了血清样本中3种靶标同时检测的标准工作曲线,AFP、CEA和CA19-9的检出限分别达到0.1μg/L、0.1μg/L和30 U/mL,线性范围跨越4个数量级。微流体磁敏生物传感器可在30 min内完成多靶标生物标志物检测,临床血清样本的测试结果与ELISA法一致,具有检测时间短、灵敏度高的优点。     

玻璃微-纳流控芯片的制备及在蛋白质电动富集中的应用

发展了一种以"二次刻蚀"技术制备玻璃微-纳流控芯片的新方法. 首先, 采用紫外光刻和化学湿法刻蚀技术在玻璃基片上加工微米深度的微通道; 去除剩余的光胶后, 在刻有微通道的基片上旋涂一层新的光胶; 再通过二次紫外光刻和湿法刻蚀在该基片上加工深度小于100 nm的纳通道; 最后, 采用室温键合技术, 将带有微纳结构的基片与盖片封合制成玻璃微-纳流控复合芯片. 利用本方法可以在普通化学实验室以简易的设备制得具有微-纳米复合结构的玻璃芯片. 将此玻璃微-纳流控复合芯片成功地应用于以电动离子捕集技术富集荧光素钠异硫氰酸酯(FITC)标记的人血清蛋白(HSA). 结果表明, 对于0.5 mg/mL的FITC-HSA, 30 s内富集倍率可达到200倍以上.     

Biofunctionalization of electrowetting-on-dielectric digital microfluidic chips for miniaturized cell-based applications

In this paper we report on the controlled biofunctionalization of the hydrophobic layer of electrowetting-on-dielectric (EWOD) based microfluidic chips with the aim to execute (adherent) cell-based assays. The biofunctionalization technique involves a dry lift-off method with an easy to remove Parylene-C mask and allows the creation of spatially controlled micropatches of biomolecules in the Teflon-AF(?) layer of the chip. Compared to conventional methods, this method (i) is fully biocompatible; and (ii) leaves the hydrophobicity of the chip surface unaffected by the fabrication process, which is a crucial feature for digital microfluidic chips. In addition, full control of the geometry and the dimensions of the micropatches is achieved, allowing cells to be arrayed as cell clusters or as single cells on the digital microfluidic chip surface. The dry Parylene-C lift-off technique proves to have great potential for precise biofunctionalization of digital microfluidic chips, and can enhance their use for heterogeneous bio-assays that are of interest in various biomedical applications.     

A decade of microfluidic analysis coupled with electrospray mass spectrometry: an overview

This review presents a thorough overview covering the period 1997-2006 of microfluidic chips coupled to mass spectrometry through an electrospray interface. The different types of fabrication processes and materials used to fabricate these chips throughout this period are discussed. Three 'eras' of interfaces are clearly distinguished. The earliest approach involves spraying from the edge of a chip, while later devices either incorporate a standard fused-silica emitter inserted into the device or fully integrated emitters formed during chip fabrication. A summary of microfluidic-electrospray devices for performing separations and sample pretreatment steps before sample introduction into the mass spectrometer is also presented.     

Initial study of two-phase laminar flow extraction chip for sample preparation for gas chromatography

A sample preparation method for gas chromatography using a two-phase, laminar flow extraction PDMS/glass chip has been developed. A stable two-phase laminar interface was obtained by surface modification, and the organic extraction phase and the aqueous sample phase were separated effectively when the two-phase laminar flows exit the chip. Experiments were conducted on the chip to extract ephedrine from aqueous solution. Good reproducibility was obtained over the entire range of ephedrine concentration using the extraction chips (CV range 2.7%-4.5%). Effects of salt and solvent on extraction efficiency were studied.     

Accurate dispensing of volatile reagents on demand for chemical reactions in EWOD chips

Digital microfluidic chips provide a new platform for manipulating chemicals for multi-step chemical synthesis or assays at the microscale. The organic solvents and reagents needed for these applications are often volatile, sensitive to contamination, and wetting, i.e. have contact angles of <90° even on the highly hydrophobic surfaces (e.g., Teflon? or Cytop?) typically used on digital microfluidic chips. Furthermore, often the applications dictate that the processes are performed in a gas environment, not allowing the use of a filler liquid (e.g., oil). These properties pose challenges for delivering controlled volumes of liquid to the chip. An automated, simple, accurate and reliable method of delivering reagents from sealed, off-chip reservoirs is presented here. This platform overcomes the issues of evaporative losses of volatile solvents, cross-contamination, and flooding of the chip by combining a syringe pump, a simple on-chip liquid detector and a robust interface design. The impedance-based liquid detection requires only minimal added hardware to provide a feedback signal to ensure accurate volumes of volatile solvents are introduced to the chip, independent of time delays between dispensing operations. On-demand dispensing of multiple droplets of acetonitrile, a frequently used but difficult to handle solvent due to its wetting properties and volatility, was demonstrated and used to synthesize the positron emission tomography (PET) probe [(18)F]FDG reliably.     

A high-pressure interconnect for chemical microsystem applications

A PEEK interface for use in microfluidic applications is designed, fabricated and tested. The interface allows for the facile, non-permanent coupling of standard capillary tubing to silicon/glass micromixer chips. Importantly, the interface provides for a secure connection between capillary lines and chip reservoirs without the need for any adhesive materials. Furthermore, when used in conjunction with silicon/glass micromixer chips fluidic transport is stable over a wide range of volumetric flow rates (1-1500 microL min(-1)), and the entire construct can be rapidly assembled and disassembled at any time during the course of experimentation.     

A micro surface tension pump (MISPU) in a glass microchip

A non-membrane micro surface tension pump (MISPU) was fabricated on a glass microchip by one-step glass etching. It needs no material other than glass and is driven by digital gas pressure. The MISPU can be seen working like a piston pump inside the glass microchip under a microscope. The design of the valves (MISVA) and pistons (MISTON) was based on the surface tension theory of the micro surface tension alveolus (MISTA). The digital gas pressure controls the moving gas-liquid interface to open or close the input and output MISVAs to refill or drive the MISTON for pumping a liquid. Without any moving parts, a MISPU is a kind of long-lasting micro pump for micro chips that does not lose its water pumping efficiency over a 20-day period. The volumetric pump output varied from 0 to 10 nl s(-1) when the pump cycle time decreased from 5 min to 15 s. The pump head pressure was 1 kPa.     

CE chips fabricated by injection molding and polyethylene/thermoplastic elastomer film packaging methods

This study presents a new packaging method using a polyethylene/thermoplastic elastomer (PE/TPE) film to seal an injection-molded CE chip made of either poly(methyl methacrylate) (PMMA) or polycarbonate (PC) materials. The packaging is performed at atmospheric pressure and at room temperature, which is a fast, easy, and reliable bonding method to form a sealed CE chip for chemical analysis and biomedical applications. The fabrication of PMMA and PC microfluidic channels is accomplished by using an injection-molding process, which could be mass-produced for commercial applications. In addition to microfluidic CE channels, 3-D reservoirs for storing biosamples, and CE buffers are also formed during this injection-molding process. With this approach, a commercial CE chip can be of low cost and disposable. Finally, the functionality of the mass-produced CE chip is demonstrated through its successful separation of phiX174 DNA/HaeIII markers. Experimental data show that the S/N for the CE chips using the PE/TPE film has a value of 5.34, when utilizing DNA markers with a concentration of 2 ng/microL and a CE buffer of 2% hydroxypropyl-methylcellulose (HPMC) in Tris-borate-EDTA (TBE) with 1% YO-PRO-1 fluorescent dye. Thus, the detection limit of the developed chips is improved. Lastly, the developed CE chips are used for the separation and detection of PCR products. A mixture of an amplified antibiotic gene for Streptococcus pneumoniae and phiX174 DNA/HaeIII markers was successfully separated and detected by using the proposed CE chips. Experimental data show that these DNA samples were separated within 2 min. The study proposed a promising method for the development of mass-produced CE chips.     

Analytical and numerical study of Joule heating effects on electrokinetically pumped continuous flow PCR chips

Joule heating is an inevitable phenomenon for microfluidic chips involving electrokinetic pumping, and it becomes a more important issue when chips are made of polymeric materials because of their low thermal conductivities. Therefore, it is very important to develop methods for evaluating Joule heating effects in microfluidic chips in a relatively easy manner. To this end, two analytical models have been established and solved using the Green's function for evaluating Joule heating effects on the temperature distribution in a microfluidic-based PCR chip. The first simplified model focuses on the understanding of Joule heating effects by ignoring the influences of the boundary conditions. The second model aims to consider practical experimental conditions. The analytical solutions to the two models are particularly useful in providing guidance for microfluidic chip design and operation prior to expensive chip fabrication and characterization. To validate the analytical solutions, a 3-D numerical model has also been developed and the simultaneous solution to this model allows the temperature distribution in a microfluidic PCR chip to be obtained, which is used to compare with the analytical results. The developed numerical model has been applied for parametric studies of Joule heating effects on the temperature control of microfluidic chips.     

Building addressable libraries: spatially isolated, chip-based reductive amination reactions

A Pd(II) reagent has been generated at preselected sites on an electrochemically addressable chip and used to effect the oxidation of the neighboring alcohols on the polymer coating the chip's surface. The resulting carbonyls were then used to accomplish site-selective reductive amination reactions on the chips. The work demonstrates that the confinement strategy developed for spatially isolated Wacker oxidations to specific sites on the chips is general and can be used for other Pd(II)-based reactions.     

Development of high-frequency true-linear generator for electrochemical purposes

A new design for a true-linear generator suitable for electrochemical measures is presented. The main component of generation system is an MAX038 chip, a high-frequency relaxation-type oscillator. The design is completed with a digital interface for computer control and an output stage to make signal suitable for cyclic voltammetry experiments. A digital circuit is also included to obtain single sweep signals by isolating one period or a half-period from continuous original output. Performance of presented generator is tested up to 1 MV s(-1) obtaining good stability and linearity.