稳定微环境微流控细胞培养芯片的设计与制备

为了解决细胞体外培养微环境不稳定的问题,利用微流控技术设计并成功制备出了具有稳定微环境的细胞培养芯片.该芯片在主流道中设置了四边形培养腔结构,细胞培养腔周围设计了狭缝宽度小于细胞尺寸的微柱阵列.细胞培养腔周围的狭缝形成了多个输运通道,微流体以对流扩散的方式通过微柱阵列之间的多个通道同时进出培养腔,为细胞及时地供给营养物质和移除废液.利用COMSOL Multiphysics软件对该结构和传统单通道结构模型培养腔内微流体的速度场和压力场进行了仿真分析,并采用粒子图像测速法测量了该结构培养腔内微流体的平均速度.结果表明:该芯片培养腔内微流体的速度稳定且分布均匀,并能有效抵抗外部扰动.     

基于低温直接键合的血细胞计数芯片结构制备

研究了一种新颖的微流管道血细胞计数器的结构及其工作原理,采用流体动力学对其液体分层流动特性进行了仿真分析,结合图形制备和低温直接键合工艺制作了硅基微流体管道血细胞计数器结构,并采用红外透射方法对微流体管道结构进行了检测.对封闭管道的流通性及结构的键合强度也进行了测量.研究分析表明,采用上述工艺制备的微流体芯片结构与电子器件兼容性好,具有良好的化学惰性和热稳定性,而且管道结构规则,精度高,键合界面层薄,具有较好的应用前景.     

热电冷却微流体芯片的温度响应特性优化研究

精确的温度调控是微流体技术在生化分析和医学诊断等方面发展应用的重要保障。为实现微流体芯片目标区域的温度控制,本文设计了基于异型结构热电制冷器的微流体芯片温度控制系统,通过数值模拟和实验测试分析了该温控系统的传热特性及及温度响应特性。研究结果表明：采用的热电制冷器可将微流体芯片样品池的温度降至-24 ℃,但样品池的降温速率远小于热电制冷器的冷端降温速率,存在温度响应迟滞问题。为此,进一步提出了带有聚冷结构的系统优化,结果表明：聚冷结构的引入虽然会带来少量的冷量损失,但可以显著提升该温控系统的温度响应速率,有效减少响应时间。对于T型聚冷结构,当下底直径为14 mm和10 mm时,可分别将温度响应时间减少30%和40.7%。     

新型网状通道微流控细胞培养芯片设计与制作

微流控芯片能为细胞的体外培养提供良好的生长微环境.设计制作了一系列具有网状微通道网络的细胞培养微流控芯片,为细胞体外培养提供了稳定的流体环境.该芯片由网状微通道网络和处于网状通道节点处的培养腔室组成.芯片整体结构呈对称分布,外部流体在驱动力的作用下进入微通道网络,经过多条微通道进入培养池.培养池周围微通道具有"多入多出"的特点,在很大程度上提高了培养池内流场的稳定性.同时研究了芯片微通道网络的网状程度、培养腔数量对培养池内流场的影响.结果表明:处于网状微通道网络上的培养池内流场均一稳定,能为细胞体外培养提供近体微环境.     

微间隙结构的温度场测量与分析

随着高功率、高性能集成电路的快速发展,芯片的散热面临着巨大挑战。微间隙结构具有长度和宽度尺寸较大、高度尺寸微小的特点,容易在芯片散热面构造,有利于实现高热导率的微流体散热。本文提出了微间隙结构温度场的测量方法,采用3×3阵列的9个0603型贴片式温度传感器,测量在两相流通过被热源加热的微间隙结构时的温度场。微间隙的四个角的温度最高,中间区域温度较低。微间隙的温度场分布为两个区域:有效散热区和热点区,呈"十"字型分布。研究了微间隙结构在气液两相流的散热技术下的散热性能及特点,并得出气液两相流在微间隙中的散热效果优于单相流。     

粗糙度对微流道内流体连续自搬运的影响

微流控芯片中各功能单元间样品的运输依赖于流体在微通道中的流动,尺度效应加剧表面作用效果,使得微流道内流体无需外部动力即可实现连续铺展搬运。为了深入研究微流道内流体的流动机制和动力学特性,分析影响微流道内流体自搬运效率的因素,基于近似Derjaguin法的同时充分考虑表面能和Casimir效应,利用数值计算和实验相结合的方法分析了微流道内壁粗糙度对流体流动特性和自搬运效率的影响,明确了微流道内流体的本构方程和流动控制方程,并设计搭建实验台验证所得结果的有效性和可靠性。结果表明：内壁粗糙度是影响微流道内流体流动特性和连续自搬运效率的重要因素;当粗糙度等效齿数、等效齿高和等效齿倾角变化时,微流道内近壁面齿隙间的主漩涡和伴生涡都相应改变,导致流体自搬运效率发生相应变化。研究结果对解决微流控润滑和微流控芯片减阻防粘等设计和使用问题具有重要理论指导意义,对微电子机械系统的小型化和集成化设计具有一定的参考价值。     

分析芯片微通道制作技术进展

微通道制作是微分析芯片制作中的关键技术之一。就选取材料的原则，模板复制中的模具制造技术及微通道直接加工方法做了比较，提出了微流体芯片产业化的可行性方案。     

应用微流体混合器芯片于食品中甲醛含量快速检测

本研究利用微流体芯片配合雷射激发荧光侦测法,侦测食品中不当添加物一甲醛,实验中以4-amino-3-penten-2-one(Fluoral-P)和甲醛作用,并于微流体混合器中进行反应及荧光衍生化以快速侦测.在微流体芯片中过高浓度甲醛荧光衍生物,因荧光分子基团讯号集中,易干扰全波长与荧光的侦测,因此在微流体芯片的检测以100 ppm以下为主.而在微流体混合器方面,本研究利用1:7型式不对称管道之微流体混合器,甲醛于此芯片中行荧光侦测法测定,随着甲醛浓度的降低,荧光讯号愈平缓,易出现噪声,侦测极限可达0.4 ppm且其线性度为R2=0.9954,而浓度低于1 ppm时,其S/N比表现度随之降低,此系统可提供较短分析时间、低试剂与成本消耗.     

仿生蜘蛛丝微纳米复合材料的集水性能

水是自然界大多数生物生存的必要条件,而动植物界存在着诸多奇妙的浸润现象。仿生微纳米复合材料浸润性相关研究是近年来国内外发展迅速的前沿热点,涉及跨领域、交叉领域。本文对仿生工程领域拥有集水性能的类蜘蛛丝微纳米复合材料的研究进展进行了评述,简要分析了材料的微纳米复合结构及其控制浸润性/液滴行为的机制,总结了类蜘蛛丝微纳米复合材料及集成蜘蛛网的制备技术发展(包括提拉法、静电纺丝法、微流体技术、三维编织技术、3D打印技术等),展示了不同微纳米复合材料及相应集水性能。本文重点分析并对比了仿生蜘蛛丝微纳米复合材料的仿生结构设计、材料制备技术、集水性能等,并展望了拥有集水性能的微纳米复合材料在微流体芯片、天气预报、海水淡化、药物缓释、微反应器、能量储运与转换等多领域的进一步新兴、多功能化应用。     

芯片水冷式微通道散热器的优化设计

随着电子芯片的高度集成化,散热问题日益凸显,芯片微通道水冷技术以其优越的散热性能被广泛应用。然而由于水冷散热器体积小,流体在散热器内流动形式复杂,使得散热器的设计加工和性能测试在常规条件下存在一定的局限性。本文对影响散热器性能的2个主要因素——冷却水进出口方式和微通道的结构参数进行分析,运用ANSYS软件进行模拟与设计优化,得到散热器的最优结构参数,为微通道水冷散热器的优化设计提供理论依据。     

Lensfree sensing on a microfluidic chip using plasmonic nanoapertures

We demonstrate lensfree on-chip sensing within a microfluidic channel using plasmonic nanoapertures that are illuminated by a partially coherent quasimonochromatic source. In this approach, lensfree diffraction patterns of metallic nanoapertures located at the bottom of a microfluidic channel are recorded using an optoelectronic sensor-array. These lensfree diffraction patterns can then be rapidly processed, using phase recovery techniques, to back propagate the optical fields to an arbitrary depth, creating digitally focused complex transmission patterns. Cross correlation of these patterns enables lensfree on-chip sensing of the local refractive index surrounding the near-field of the plasmonic nanoapertures. Based on this principle, we experimentally demonstrate lensfree sensing of refractive index changes as small as ～2×10(-3). This on-chip sensing approach could be quite useful for development of label-free microarray technologies by multiplexing thousands of plasmonic structures on the same microfluidic chip, which can significantly increase the throughput of sensing.     

Self-assembled colloidal arrays as three-dimensional nanofluidic sieves for separation of biomolecules on microchips

We report on a biomolecular sieving system based on the use of ordered colloidal arrays to define the sieve structure within a microfluidic device. A facile microfluidic colloidal self-assembly strategy has been developed to create ordered, robust, three-dimensional nanofluidic sieves within microfluidic devices, with which fast separation of DNA and proteins of a wide size range was achieved. Compared to conventional colloidal deposition procedures, such as vertical deposition, this approach features much faster assembling speed, the absence of drying-caused cracks that may jeopardize the separation performance, and better flexibility to couple with current microfabrication techniques. The flexibility of pore size enabled by this methodology provides separation of biomolecules with a wide size distribution, ranging from proteins (20-200 kDa) to dsDNA (0.05-50 kbp). Under moderate electric fields, complete separation can be finished in minutes, with separation efficiency comparable to gel/polymer-filled or micro-/nanofabricated microsystems. To our knowledge, this is the first demonstration of size separation of biomolecules within self-assembled ordered colloidal lattices embedded within a microfluidic system.     

High-efficiency single-cell entrapment and fluorescence in situ hybridization analysis using a poly(dimethylsiloxane) microfluidic device integrated with a black poly(ethylene terephthalate) micromesh

Here, we report a high-efficiency single-cell entrapment system with a poly(dimethylsiloxane) (PDMS) microfluidic device integrated with a micromesh, and its application to single-cell fluorescence in situ hybridization (FISH) analysis. A micromesh comprising of 10 x 10 microcavities was fabricated on a black poly(ethylene terephthalate) (PET) substrate by laser ablation. The cavity was approximately 2 microm in diameter. Mammalian cells were driven and trapped onto the microcavities by applying negative pressure. Trapped cells were uniformly arrayed on the micromesh, enabling high-throughput microscopic analysis. Furthermore, we developed a method of PDMS surface modification by using air plasma and the copolymer Pluronic F-127 to prevent nonspecific adsorption on the PDMS microchannel. This method decreased the nonspecific adsorption of cells onto the microchannel to less than 1%. When cells were introduced into the microfluidic device integrated with the black PET micromesh, approximately 70-80% of the introduced cells were successfully trapped. Moreover, for mRNA expression analysis, on-chip fluorescence in situ hybridization (e.g., membrane permeabilization, hybridization, washing) can be performed in a microfluidic assay on an integrated device. This microfluidic device has been employed for the detection of beta-actin mRNA expression in individual Raji cells. Differences in the levels of beta-actin mRNA expression were observed in serum-supplied or serum-starved cell populations.     

Microfluidic devices connected to fused-silica capillaries with minimal dead volume

Fused-silica capillaries have been connected to microfluidic devices for capillary electrophoresis by drilling into the edge of the device using 200-μm tungsten carbide drills. The standard pointed drill bits create a hole with a conical-shaped bottom that leads to a geometric dead volume of 0.7 nL at the junction, and significant band broadening when used with 0.2-nL sample plugs. The plate numbers obtained on the fused-silica capillary connected to the chip were about 16-25% of the predicted numbers. The conical area was removed with a flat-tipped drill bit and the band broadening was substantially eliminated (on average 98% of the predicted plate numbers were observed). All measurements were made while the device was operating with an electrospray from the end of the capillary. The effective dead volume of the flat-bottom connection is minimal and allows microfluidic devices to be connected to a wide variety of external detectors.     

基于局部溶解性激活的聚合物微流控芯片超声波键合

利用低于临界振幅下的超声波作用在聚合物上仅产生表面热的特点,结合PMMA在异丙醇(IPA)中的温变溶解特性,提出了一种基于局部溶解性激活的超声波聚合物微流控芯片键合方法.理论分析表明当超声振幅小于临界振幅时,只有器件接触表面产生局部表面热,而且在70℃附近IPA对PMMA的溶解性才具有良好的激活作用.在试验研究中,利用精密加工法和热压法制作了带面接触式导能筋结构和80μm×80μm微通道的PMMA微流控芯片基片.在超声振幅为13μm、键合时间8 s、键合压力300 N的条件下进行了键合试验.结果表明,芯片拉伸强度达2.25 MPa,微通道的承压能力超过800 kPa,键合后导能筋无熔融,微沟道变形率小于2%,键合时间仅为8s.该方法的键合强度和键合效率明显高于传统的键合方法,而微结构的变形率却较小,故可作为一种具有产业化前景的聚合物MEMS器件快速封接方法.     

微流体衍射相位显微成像及其在寄生虫测量中的应用

本文提出了一种将衍射相位显微技术与微流体芯片相结合的方法对水源性寄生虫进行定量测量。结合干涉技术与光学显微镜搭建了衍射相位显微成像系统,实现对寄生虫的高灵敏度实时测量。基于光刻工艺,设计和制作了U型捕获结构双层微流体芯片,实现高通量的单个寄生虫捕获。将与聚二甲基硅氧烷(PDMS)折射率相同的聚蔗糖水溶液通入微腔,消除U型捕获结构边缘衍射在相位成像时产生的显著干扰噪声。利用不同直径的标准聚苯乙烯微球验证了该系统的准确性,最大相位值误差不超过3%。采用上述系统测量了100个贾第鞭毛虫包囊和100个隐孢子虫卵囊,然后从干涉图中重构出两虫的相位图。通过对定量相位图的分析得出两虫的形态学参数与定量的光体积差分布,定量的数据为了解其生理特性提供了依据。微流体衍射相位显微成像系统结构简单,稳定性好,测量精度高,在对单个微生物进行实时监测和无标记定量研究方面具有巨大的潜力。     

Electroporation of mammalian cells in a microfluidic channel with geometric variation

Electroporation has been widely used to load impermeant exogenous molecules into cells. Rapid electrical lysis based on electroporation has also been applied to analyze intracellular materials at single-cell level. There has been increasing demand to implement electroporation in a microfluidic format as a basic tool for applications ranging from screening of drugs and genes to studies of intracellular dynamics. In this report, we have developed a simple technique to electroporate mammalian cells with high throughput on a microfluidic platform. In our design, electroporation only happened in a defined section of a microfluidic channel due to the local field amplification by geometric variation. The time of exposure of the cells to this high field was determined by the velocity of the cells and the length of the section. The change in the cell morphology during electroporation was observed in real time. We determined that electroporation of Chinese hamster ovary cells occurred when the local field strength was increased to approximately 400 V/cm. The internalization of membrane-impermeant molecules (SYTOX green) with cell viability preserved was also carried out to demonstrate transient electropermeabilization. The influence of the operational parameters of the device on cell viability was determined. A large percentage of cells remained viable after electroporation when the parameters were tuned. We also studied rapid cell lysis when the field intensity was in the range of 600-1200 V/cm. The rupture of cell membrane happened within 30 ms when the field strength was 1200 V/cm. Given the simplicity, high throughput, and high compatibility with other devices, this microfluidic electroporation technique may increase the application of microfluidic systems in screening of drugs and biomolecules and chemical cytometry.     

Multiple open-channel electroosmotic pumping system for microfluidic sample handling

The development of a novel, fully integrated, miniaturized pumping system for generation of pressure-driven flow in microfluidic platforms is described. The micropump, based on electroosmotic pumping principles, has a multiple open-channel configuration consisting of hundreds of parallel, small-diameter microchannels. Specifically, pumps with microchannels of 1-6 microm in depth, 4-50 mm in length, and an overall area of a few square millimeters, were constructed. Flow rates of 10-400 nL/min were generated in electric-field-free regions in a stable, reproducible and controllable manner. In addition, eluent gradients were created by simultaneously using two pumps. Pressures up to 80 psi were produced with the present pump configurations. The pump can be easily interfaced with other operational elements of a micrototal analysis system (micro-TAS) device with multiplexing capabilities. A new microfluidic valving system was also briefly evaluated in conjunction with these pumps. The micropump was utilized to deliver peptide samples for electrospray ionization-mass spectrometric (ESI-MS) detection.     

Transport, location, and quantal release monitoring of single cells on a microfluidic device

A novel microfluidic device has been developed for on-chip transport, location, and quantal release monitoring of single cells. The microfluidic device consists of a plate of PDMS containing channels for introducing cells and stimulants and a glass substrate into which a cell micro-chamber was etched. The two tightly reversibly sealed plates can be separated for respective cleaning, which significantly extends the lifetime of the microchip that is frequently clogged in cell analysis experiments. Using hydraulic pressure, single cells were transported and located on the microfluidic chip. After location of a single PC12 cell on the microfluidic chip, the cell was stimulated by nicotine that was also introduced through the micro-channels, and the quantum release of dopamine from the cell was amperometricly detected with our designed carbon fiber microelectrode. The results have demonstrated the convenience and efficiency of using the microfluidic chip for monitoring of quantal release from single cells and have offered a facile method for the analysis of single cells on microfluidic devices.     

Microfluidic approach to genotyping human platelet antigens

Centralised laboratories routinely determine blood types by serological and molecular methods. Current practices have limitations in terms of cost, time and accessibility. Miniaturised microfluidic platforms offer an alternative to conventional genotyping methods, since they consume fewer reagents, provide faster analysis and allow for complete integration and automation. As these 'lab-on-a-chip' devices have been used for bacterial and viral detection, the authors investigated blood group genotyping as a novel application of microfluidic technology. To demonstrate the feasibility of microfluidic chip-based genotyping, the authors compared human platelet antigen 1 (HPA-1) genotype results from conventional and chip-based analysis for 19 blood donor specimens. DNA purification was performed with ChargeSwitch? magnetic beads, DNA amplification (PCR), restriction length polymorphism (RFLP) and capillary electrophoresis (CE) for identification of the DNA on microfluidic chips. It was found that nine donors were HPA-1a/1a and ten were HPA-1a/1b. Concordance between the conventional and on-chip methods was achieved for all but one sample. All the steps were demonstrated for complete blood group genotyping analysis of patient whole blood specimens on separate microfluidic chips. Future work will focus on integration of all the genotyping protocols on a single microfluidic chip.