Fabrication of microfluidic chip using micro‐hot embossing with micro electrical discharge machining mold

This study develops an improved method for generating aluminum mold inserts used in the replication of polymer‐based microfluidic chip. Since molding masters that are suitable for microfluidic chip replication must have features whose dimensions are of the order of tens to hundreds of microns, micro electrical discharge machining is employed herein to fabricate an aluminum mold insert of a microfluidic chip. The width and depth of the aluminum mold insert for the microfluidic chip are 61.50 and 49.61 µm, respectively. The surface roughness values of the microchannel and the sample reservoir in aluminum mold insert for the microfluidic chip are 53.9 and 34.3 nm, respectively. PMMA material is adopted as the molded microfluidic chip that is produced by micro‐hot embossing molding. The PMMA material can replicate the microchannel and sample reservoir very well when the aluminum mold insert is used in micro‐hot embossing molding. The results indicate that the most important parameter in the replication of molded microfluidic chip is the embossing pressure, which is also the most important parameter in determining the surface roughness of the molded microfluidic chip. Copyright © 2010 John Wiley & Sons, Ltd.     

蛋白质DNA混合微点阵和微流控芯片的整合

在活化的石英片上制作蛋白质和DNA微点阵, 并可逆地将其与含有通道的多聚二甲基硅氧烷弹性橡胶封接在一起, 使蛋白质和DNA微点阵组装在微通道列阵内; 实现在微通道列阵内同时检测和分析蛋白质与DNA的功能. 为了降低多聚二甲基硅氧烷弹性橡胶的疏水性, 增强其生物相容性, 实验通过多聚赖氨酸对多聚二甲基硅氧烷弹性橡胶的修饰, 提高了它的亲水性, 使溶液能够在微通道内顺畅地流通. 实验表明, 这种混合芯片能够提高检测速度和增加检测的信息量.     

Prototypical Nonelectrochemical Method for Surface Regeneration of an Integrated Electrode in a PDMS Microfluidic Chip

Abstract

A prototypical method for surface regeneration of an integrated electrode in a microfluidic chip is demonstrated. A platinum wire as working electrode was mounted in a polydimethylsiloxane chip vertical to the chip through the channel. The regeneration of the electrode was easily achieved by drawing the platinum wire out for 5 mm, because the area exposed to the channel or the stream would be altered. With continuous motion, the wire electrode can maintain a fresh surface just like a dropping mercury electrode. The current–time curve and open circuit potential (OCP) of dopamine solution show the performance of this prototypical system.     

Micro fabrication of microlens arrays by micro dispensing

In this study, master of the microlens arrays is fabricated using micro dispensing technology, and then electroforming technology is employed to replicate the Ni mold insert of the microlens arrays. Finally, micro hot embossing is performed to replicate the molded microlens arrays from the Ni mold insert. The resin material is used as the dispensing material, which is dropped on a glass substrate. The resin is exposed to a 380 W halogen light. It becomes convex under surface tension on the glass substrate. A master for the microlens arrays is then obtained. A 150‐nm‐thick copper layer is sputtered on the master as an electrically conducting layer. The electroforming method replicates the Ni mold insert from the master of the microlens arrays. Finally, micro hot embossing is adopted to replicate the molded microlens arrays. The micro hot embossing experiment employs optical films of polymethylmethacrylate (PMMA) and polycarbonate (PC). The processing parameters of micro hot embossing are processing temperature, embossing pressure, embossing time, and de‐molding temperature. Taguchi's method is applied to optimize the processing parameters of micro hot embossing for molded microlens arrays. An optical microscope and a surface profiler are utilized to measure the surface profile of the master, the Ni mold insert and the molded microlens arrays. AFM is employed to measure the surface roughness of the master, the Ni mold insert and the molded microlens arrays. The sag height and focal length are determined to elucidate the optical characteristics of the molded microlens arrays. Copyright © 2009 John & Sons, Ltd.     

Microfluidic chip accomplishing self-fluid replacement using only capillary force and its bioanalytical application

A polymer microfluidic chip accomplishing automated sample flow and replacement without external controls and an application of the chip for bioanalytical reaction were described. All the fluidic operations in the chip were achieved by only natural capillary flow in a time-planned sequence. For the control of the capillary flow, the geometry of the channels and chambers in the chip was designed based on theoretical considerations and numerical simulations. The microfluidic chip was made by using polymer replication techniques, which were suitable for fast and cheap fabrication. The test for a biochemical analysis, employing an enzyme (HRP)-catalyzed precipitation reaction, exhibited a good performance using the developed chip. The presented microfluidic method would be applicable to biochemical lab-on-a-chips with integrated fluid replacement steps, such as affinity elution and solution exchange during biosensor signaling.     

基于毛细管电泳及微流控芯片的药物提取分离技术

近年来,在提取分离方面出现了许多新技术和新方法.其中毛细管电泳和微流控芯片技术以其微量、高效、快速等特点,在药物提取分离中已渐显优势.该文对基于毛细管电泳和微流控芯片的两相电泳技术、微流控液液萃取技术、微流控固液萃取技术、微流控过滤式分离技术、微流控膜分离技术在药物分离提取中的应用进行了综述.     

微流控SERS芯片的设计制备及其在细菌检测中的应用

微流控芯片分析平台与表面增强拉曼散射(Surface enhanced Raman scattering,SERS)光谱分析方法结合,充分利用了SERS法所具备的样品前处理简便、检测无损、成分辨识度高以及适宜水环境检测等优点,在生化分析检测领域备受关注。微流控SERS芯片设计及芯片上SERS增强基质的制备是构建微流控SERS芯片分析方法和系统的关键,也是提高检测灵敏度和可重复性的核心问题。该文在介绍微流控SERS芯片的基本构型和功能的基础上,重点综述了微流控SERS芯片上SERS基质的制备方法及其测试效果。基于微电子机械系统(Micro-Electro-mechanical-System,MEMS)加工技术制备的SERS基质,具有纳米粒径有序可控、便于集成制备但增强基质材料种类有限的特点;基于化学沉积和自组装等理化方法制备的SERS基质具有基质种类易拓展、成本低、与微流控通道结合方法灵活等特点。在这些基础上构建的微流控SERS芯片及其分析测试方法和系统,在细菌等许多生化检测领域显示出强大的发展潜力。     

微流控纸芯片的加工及其分析应用的实验设计*

设计了一个使用喷墨打印法加工微流控纸芯片的实验,在经烷基烯酮二聚体(AKD)的正己烷溶液浸泡过的滤纸上,以三乙醇胺溶液为打印墨水,用喷墨打印机打印出设计好的芯片图案。滤纸加热后,打印区域呈现亲水性,非打印区域为疏水性,从而制备出纸芯片,用该纸芯片通过数字比色法实现了亚硝酸根离子的定量测定。该实验不使用昂贵仪器设备,易普及。通过实验,促使学生了解微流控芯片这一前沿科学技术,锻炼学生细致、灵巧的动手能力,激发学生科技创新活力。     

玻璃微流控芯片廉价快速制作方法的研究

研究了一种玻璃微流控芯片的快速、低成本制作工艺和方法. 该方法采用商品化的显微载玻片(soda-lime玻璃)作为芯片基质材料, 利用AZ 4620光刻胶代替传统工艺中的溅射金属层或多晶硅/氮化硅层作为玻璃刻蚀的掩膜层, 同时利用一种紫外光学胶键合方法代替传统熔融键合方法实现芯片的键合, 整个工艺对玻璃基质材料要求低, 普通微流控芯片(深度小于50 μm)制作流程仅需约3.5 h, 可降低制作成本, 缩短制作周期. 还系统地研究了光刻胶厚度、光刻胶硬烘时间和玻璃腐蚀液配比对玻璃微流控芯片制作的影响, 获得了优化的工艺参数.     

微流控芯片实验室在基因分析研究中的应用

对微流控芯片实验室在基因分析中应用研究的最新进展予以综述,特别注意到了这种新技术平台在不同类型的基因多态性检测和脱氧核糖核酸(DNA)测序中的贡献,在一定程度上反映了这种贡献在临床诊断、法医学鉴定等领域已经产生的影响。     

微流控芯片简易安培检测器的制作及对烟酰胺片中烟酰胺的测定

搭建了微流控芯片简易安培检测器,并用于市售药品烟酰胺片中烟酰胺含量的测定。由碳纳米管微圆盘电极和钛管组成集成双电极,中间的碳纳米管微圆盘电极作为安培检测的工作电极,外套的钛管既作为安培检测的对极,又充当分离高压电源的地极,使其结构更加简化和微型化。优化了缓冲溶液种类、浓度,分离电压及进样时间等实验条件。结果表明,在10 mmol·L-1磷酸盐缓冲液(pH 7.8)中,进样10 s,在2.0kV电压下分离,烟酰胺在2 min内可实现较好的分离和检测,其线性范围为10~600μmol·L-1,检出限(S/N=3)为5.0μmol·L-1,相对标准偏差(RSD)为3.0%,平均加标回收率为99.1%。该装置实现了微型化和集成化,并具有检测灵敏度较高、选择性好、成本低等特点,可用于药品的质量控制。     

基于纳米金催化的血清尿酸纸芯片的构建及应用

建立了一种以纸芯片为平台,利用纳米金(Au NPs)的过氧化物模拟酶特性对血清中尿酸(UA)含量进行快速检测的方法.在改装的中性笔中灌注疏水性材料溶液,直接在滤纸上绘制所需要的图案,经干燥后形成纸芯片.将纳米金、四甲基联苯胺(TMB)和H_2O_2的混合液依次滴加于纸芯片检测区域,无色的TMB被氧化成蓝色,然后将待测样品滴加于蓝色区域,氧化态TMB被还原为无色,根据手机相机记录的检测区域灰度值计算试样中尿酸的浓度.实验优化了纳米金在纸芯片上的用量、反应时间和反应温度等参数,在最优实验条件下,检测尿酸的线性范围为10.6~125 mg/L,检出限为4.64 mg/L,加样回收率为94.8%~108.5%.该方法选择性良好,可用于测定血清样品中尿酸的含量.     

纳米技术在毛细管电泳和微流控芯片电泳生物大分子分离中的应用*

在分离领域,纳米技术主要以两种形式改善分离效果,一种是利用金、二氧化硅、聚合物、金属氧化物和碳纳米管等纳米材料,二是通过微机电加工、化学方法或者自组装技术构筑纳米障碍物和纳通道等纳米结构。本文对两种不同形式的纳米技术在毛细管电泳和微流控芯片电泳生物分离中的应用进行了综述。并对该领域未来的发展进行了展望。     

Interfacial bonding mechanism and bonding strength of AlTiCrN coating by cathodic arc ion plating

AlTiCrN coating was prepared on the surface of YT14 tungsten carbide cutting tools by cathodic arc ion plating with Ti, Al and Cr as targets. The surface morphologies, interface energy spectrum, phase and elements' binding energy of the coatings were observed with SEM, EDS, XRD and XPS, respectively, and bonding strength of the coating interface was measured with scratch tester. The results show that the phases of AlTiCrN coating are mainly composed of AlN, CrN and TiN, the crystal plane of (111) has a strong preferred orientation. The concentrations of Al, Ti, Cr, N in the coating are higher than those in the substrate, showing the gradient diffusion distribution at the bonding interface, while C atoms of the substrate have diffused into the lattices of TiN, AlN and CrN to form an obvious interdiffusion layer, and the average bonding strength of coating interface is 57.65 N. Copyright © 2014 John Wiley & Sons, Ltd.     

DC dielectrophoresis separation of marine algae and particles in a microfluidic chip

This paper reports a microfluidic method of continuous separation of marine algae and particles by DC dielectrophoresis. The locally non-uniform electric field is generated by an insulating PDMS triangle hurdle fabricated within a PDMS microchannel. Both the particles and algae are subject to negative DEP forces at the hurdle where the gradient of local electric-field strength is the strongest. The DEP force acting on the particle or the algae depends on particles’ or algae’s volume, shape and dielectric properties. Thus the moving particles and algae will be repelled to different streamlines when passing the hurdle. In this way, combined with the electroosmotic flow, continuous separation of algae of two different sizes, and continuous separation of polystyrene particles and algae with similar volume but different shape were achieved. This first demonstration of DC DEP separation of polystyrene particles and algae with similar sizes illustrates the great influence of dielectric properties on particle separation and potentials for sample pretreatment.     

Hot embossing and thermal bonding of poly(methyl methacrylate) microfluidic chips using positive temperature coefficient ceramic heater

As a self-regulating heating device, positive temperature coefficient ceramic heater was employed for hot embossing and thermal bonding of poly(methyl methacrylate) microfluidic chip because it supplied constant-temperature heating without electrical control circuits. To emboss a channel plate, a piece of poly(methyl methacrylate) plate was sandwiched between a template and a microscopic glass slide on a positive temperature coefficient ceramic heater. All the assembled components were pressed between two elastic press heads of a spring-driven press while a voltage was applied to the heater for 10 min. Subsequently, the embossed poly(methyl methacrylate) plate bearing negative relief of channel networks was bonded with a piece of poly(methyl methacrylate) cover sheet to obtain a complete microchip using a positive temperature coefficient ceramic heater and a spring-driven press. High quality microfluidic chips fabricated by using the novel embossing/bonding device were successfully applied in the electrophoretic separation of three cations. Positive temperature coefficient ceramic heater indicates great promise for the low-cost production of poly(methyl methacrylate) microchips and should find wide applications in the fabrication of other thermoplastic polymer microfluidic devices.     

Interface features of ultrasonic flip chip bonding and reflow soldering in microelectronic packaging

Ultrasonic features in the bonding area are of interest for researchers in the field of microelectronic packaging. In this study, the interface characteristics of bonding were examined using an XD7100 X‐ray instrument and a transmission electron microscope (TEM). It was seen that bubbles were usually detected at the interfaces of the reflow‐soldered flip chip (FC), but they were not found at the interfaces of ultrasonically formed FC, and so ultrasonic FC bonding is more reliable than reflow soldering. The strong mechanical effect of ultrasonic vibration activates the dislocations in the crystalline metal lattice. Dislocation diffusion is more prominent than crystal diffusion when the temperature is relatively low during ultrasonic bonding, and therefore the processes of ultrasonic bonding enhance by several orders of magnitude. This indicates that the mechanism of ultrasonic bonding is different from the melting mechanism of reflow soldering. Copyright © 2007 John Wiley & Sons, Ltd.     

Microfluidic fabrication of polysiloxane/dimethyl methylphosphonate flame‐retardant microcapsule and its application in silicone foams

A novel and versatile route for fabricating flame‐retardant microcapsules via microfluidics technology is reported. The flame‐retardant microcapsules were prepared with a dimethyl methylphosphonate (DMMP) core and an ultraviolet‐curable (UV‐curable) polysiloxane shell. Furthermore, a UV‐curable polysiloxane was synthesized. The synthesis mechanism of UV‐curable polysiloxane and the curing mechanism of flame‐retardant microcapsules were analyzed. To verify that DMMP was encapsulated in the microcapsules, X‐ray fluorescence was used before and after microencapsulation. The resulting microcapsules were well monodispersed and exhibited a good spherical shape with a smooth surface. In addition, the size of the microcapsules decreased dramatically with an increasing flow‐rate ratio of the middle‐/inner‐phase or outer‐phase flow rate. The thermal stability of the microcapsules was worse than shell materials but superior to DMMP. Silicone foams (SiFs) with microcapsules prepared using a dehydrogenation method achieved a relatively higher limiting oxygen‐index value than the pure SiF, which indicated that the microcapsules could enhance the flame retardation of SiFs effectively. Because of the polysiloxane shell, the microcapsules had good compatibility with SiFs, and the influence of microcapsules on the mechanical properties of SiFs was unremarkable.     

水凝胶微流控芯片的快速加工及在细胞培养检测中的应用

采用具有紫外光聚合性能的聚乙二醇(PEG)基水凝胶材料, 通过紫外光聚合作用快速加工双层水凝胶微流控芯片, 并验证了其对肿瘤细胞代谢液进行检测的可行性. 与传统微流控芯片材料相比, 该水凝胶芯片材料具有更好的生物相容性及可操控性, 可直接加工成形, 在生物学领域特别是细胞培养过程控制方面具有良好的应用前景. 实验结果表明, 该水凝胶微流控芯片可在微尺度空间有效模拟细胞生长环境, 并实现对细胞连续捕获后的原位培养. 将该芯片与卟啉可视阵列传感器系统结合, 经代谢特征分析可有效区分不同种类肿瘤细胞, 实现芯片细胞培养平台上的细胞代谢指纹快速可视化传感检测.     

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.