新型压电微泵的结构设计与理论分析

微泵在微流控化学分析芯片中有很大的应用前景,日益成为人们研究的热点。从结构设计、理论分析和工艺加工3个方面研究了微阀与微泵,设计出用压电驱动和聚二甲基硅氧烷(PDMS)作为泵膜的集成微阀与微泵,其特点是原理新颖、结构简单、易于加工、操作方便。结构主要是由PDMS泵膜、硅片和压电驱动器组成,其中,PDMS既是泵膜和缓冲单元,也是主动阀片。在直流电压的驱动下,其工作状态是微阀,阻止流体的单向流通,在方波信号的驱动下,其工作状态是微泵,实现流体的吸入与泵出。给出各种几何参数、工作原理和工艺流程。     

基于微流体芯片结构的PDMS二次倒模工艺研究

研究了用于制作微流体芯片结构的聚二甲基硅氧烷(PDMS)与PDMS之间的倒模方法。首先,通过使用同一个微流体芯片模具倒出多个相同的PDMS负模结构;接着分别在各负模结构上溅射不同种类、不同厚度的金属,然后再对溅射过金属的负模上浇铸PDMS并固化以进行二次倒模,最后对二次倒模出的PDMS微流体结构表面粘连、结构完整性、尺寸等进行观测,从而通过比较得到倒模溅射所需的最佳金属和溅射金属薄膜的最优厚度。此方法倒出的PDMS微流体结构完整性好,不仅提出了一种全新的用于PDMS倒模的方法,而且解决了PDMS与PDMS之间直接倒模时所遇到的相互粘连和结构撕裂等难题。     

具有3D微纳结构PDMS阵列免疫传感芯片研制

介绍了一种简便快速加工微阵列免疫传感芯片的新方法。采用化学刻蚀技术加工具有μm级山脉状起伏和nm级表面粗糙度结构(简称为3D微纳表面)的玻璃阳模,以该阳模为模板浇注法制得表面具有3D微纳表面结构的PDMS基片,再借助于物理吸附,将抗体直接固定于该PDMS表面,形成具有3D微纳结构的PDMS微阵列免疫传感器。利用光学显微镜和原子力显微镜对玻璃阳模和PDMS基片表面形貌进行表征,研究了PDMS表面微纳结构化处理对抗体吸附能力的影响。结果表明:3D微纳结构的PDMS由于具有大的比表面积,能显著增强抗体的吸附能力。将研制所得的3D微纳表面结构的PDMS芯片用于微阵列荧光免疫分析,其灵敏度是平板PDMS的5倍。     

基于声表面波实现数字微流体的产生

数字微流体的产生是压电材料为基片的微流控芯片进行微流分析的前提,报道了在压电基片上应用声表面波技术产生数字微流体的方法.在128°旋转Y切割X传播方向的LiNbO3基片上集成PDMS微通道,在微通道出口一侧为经疏水处理的铝薄片,注射泵产生恒定流量的微流体经PDMS微通道到达铝薄片并聚集,当聚集的微流体体积足够大时,微流体克服表面张力作用下滑到达压电基片,并在中心频率为27.7 MHz叉指换能器激发的声表面波作用下输运,实现微流体的数字化.同时,理论分析了微流体在铝薄片表面上受力状况,并以水为实验对象,进行微流体数字化实验.结果表明,声表面波作用下能精确产生微升量级数字微流体,为压电微流控芯片提供了一种新的微流体引入方法.     

热膨胀驱动型微阀的设计与制备

利用IntelliSuite软件对热膨胀驱动微阀进行结构分析设计,讨论了微加热器结构等因素对于微阀的影响。利用SU—8胶成型工艺制备了聚二甲基硅氧烷(PDMS)微阀所需要的模具。热膨胀驱动微阀的制备过程分为:薄膜微加热器的金属淀积、阀腔的制备、弹性薄膜的制备和流体通道的制备四部分,详细阐述了各部分的制备工艺流程和各层之间的改性键合工艺等。通过微加工工艺提高了微阀的性能。利用蠕动泵作为流体驱动源,对微阀的性能进行验证,当阀腔驱动电压达到9 V时,实现了微阀关闭。     

基于微球均匀排布的外泌体检测微流控芯片

基于微机电系统(MEMS)微纳加工工艺和聚二甲基硅氧烷(PDMS)软刻蚀技术设计制造了一种外泌体检测芯片,芯片内部包含排列整齐的微柱阵列,用于实现微球在芯片内的均匀排布。利用该芯片成功实现了对外泌体的定量测定,检测下限可达到10~4个/m L,拟合函数的确定系数R~2为0. 996 5。与现有的芯片相比,芯片结构简单,响应快,可重现性好,避免了对外加场的依赖,有着一定的临床应用前景。     

高聚物微流控芯片上集成化气动微阀的研制

报道了一种新型的聚甲基丙烯酸甲酯(PMMA)/聚二甲基硅氧烷(PDMS)复合芯片。该芯片采用PMMA-PDMS…PDMS-PMMA的四层构型,以在芯片上集成气动微阀。具有液路和控制通道网路的PMMA基片与PDMS弹性膜间采用不可逆封接,分别形成液路半芯片和控制半芯片,而2个半芯片则依靠PDMS膜间的粘性实现可逆封接,组成带有微阀的全芯片。这种制备方法解决了制备PMMA-PDMS-PMMA三层结构芯片的封接难题,封接过程简单可靠。其控制部分和液路部分可以单独更换,可进一步降低使用成本,尤其适合一次性应用场合。初步实验表明:该微阀具有良好的开关性能和耐用性。     

微流体芯片在纤维成型方面的应用研究进展

微流体芯片可在微通道中控制、操作和检测复杂流体,具有尺寸小、效率高、集成度高、响应时间短、样品需量少等优点.除了在生物化学、有机合成、疾病检测等领域有广泛的应用之外,微流体芯片在纤维成型方面也有很大的应用潜力.在简介了微流体技术的基础上,比较了传统纺丝技术和微流体纺丝技术,综述了微流体芯片在即时纺丝、静电纺丝和蛋白质成...     

一种新的纸基微流开关及其活跃方法

提出了一种新的、基于声表面波的纸基微流开关。通过软光刻技术制作内含两个微孔的聚二甲基硅氧烷(PDMS)微架,其上固定经折叠、长度可变的纸通道。PDMS微架贴附于压电基片之上,并在待连接的两微通道之下方,折叠纸通道最低端离压电基片间距为2 mm。压电基片上采用微电子工艺光刻一对叉指换能器和反射栅。当足够强度的电信号加到叉指换能器对时,激发两相向声表面波,使得压电基片上微流体输运到折叠纸通道,改变其长度,连接其上待连通的两纸基微通道,完成开关功能。对可编程微流器件提供了一种新的编程和开关控制方法。     

光纤型微流控电泳芯片的研制

介绍了一种光纤型微流控电泳芯片,该芯片主要由两部分组成:多模光纤,PDMS基片和盖片.利用二次曝光技术制作出芯片的模具;通过浇注的方法制成电泳芯片;实现了在PDMS上制作深度不同的微流控沟道和光纤沟道,使光纤与微流控沟道能够方便地对准;利用异硫氰酸酯荧光素考察了系统的性能,最小检测浓度达到1.3×10-7mol/L,信噪比S/N=5.     

Fabrication of layered polydimethylsiloxane/perfluoropolyether microfluidic devices with solvent compatibility and valve functionality

The development of multilayer soft lithography methodology has seen polydimethysiloxane (PDMS) as the preferred material for the fabrication of microfluidic devices. However, the functionality of these PDMS microfluidic chips is often limited by the poor chemical resistance of PDMS to certain solvents. Here, we propose the use of a photocurable perfluoropolyether (PFPE), specifically FOMBLIN^® MD40 PFPE, as a candidate material to provide a solvent-resistant buffer layer to make the device substantially impervious to chemically induced swelling. We first carried out a systematic study of the solvent resistance properties of FOMBLIN^® MD40 PFPE as compared with PDMS. The comparison presented here demonstrates the superiority of FOMBLIN^® MD40 PFPE over PDMS in this regard; moreover, the results permitted to categorize solvents in four different groups depending on their swelling ratio. We then present a step-by-step recipe for a novel fabrication process that uses multilayer lithography to construct a comprehensive solvent-resistant device with fluid and control channels integrated with a valve structure and also permitting easy establishment of outside connections.     

Influence of tool fabrication process on characteristics of hot embossed polymer microfluidic chips for electrospray

Fabrication techniques for mass manufacture of disposable polymer microfluidic chips are important for electrospray application used in mass spectrometry. Hot embossing offers advantages over traditional MEMS fabrication techniques and is the focus of this research. The aim of the paper is to evaluate hot embossed open channel polymer chips using two different hot embossing tools. One tool was fabricated in nickel using the electroforming process, and the other in high carbon bright steel by laser machining technique using a pulsed Nd:YAG laser that is normally used for conventional applications. Process parameters are determined and measurement of dimensions and surface roughness of tools and chips are presented. Depending on the fabrication method, each tool exhibits its own characteristic profile feature and surface roughness. Polystyrene and polycarbonate substrates embossed with the electroformed tool exhibited lowest surface roughness of 48 nm compared to 450 nm for the laser machined tool. The embossed microfluidic chips were tested for fluid flow and electrospray and showed good performance.     

SU-8 microchannels for live cell dielectrophoresis improvements

In this work a novel highly precise SU-8 fabrication technology is employed to construct microfluidic devices for sensitive dielectrophoretic (DEP) manipulation of budding yeast cells. A benchmark microfluidic live cell sorting system is presented, and the effect of microchannel misalignment above electrode topologies on live cell DEP is discussed in detail. Simplified model of budding Saccharomyces cerevisiae yeast cell is presented and validated experimentally in fabricated microfluidic devices. A novel fabrication process enabling rapid prototyping of microfluidic devices with well-aligned integrated electrodes is presented and the process flow is described. Identical devices were produced with standard soft-lithography processes. In comparison to standard PDMS based soft-lithography, an SU-8 layer was used to construct the microchannel walls sealed by a flat sheet of PDMS to obtain the microfluidic channels. Direct bonding of PDMS to SU-8 surface was achieved by efficient wet chemical silanization combined with oxygen plasma treatment of the contact surface. The presented fabrication process significantly improved the alignment of the microstructures. While, according to the benchmark study, the standard PDMS procedure fell well outside the range required for reasonable cell sorting efficiency. In addition, PDMS delamination above electrode topologies was significantly decreased over standard soft-lithography devices. The fabrication time and costs of the proposed methodology were found to be roughly the same.

     

单泵控制聚焦流形态的微流控芯片的研制

研究一种单动力源、聚焦流形态可控的用于细胞排队的微流控芯片。建立了样品沟道与鞘流沟道不同长度比例、不同夹角的模型并进行了不同负压条件下聚焦流形态仿真,运用SPSS软件进行了回归分析并进行了模型优化。在芯片的微加工过程中,利用印刷电路板(PCB)制作了母板,以聚二甲基硅氧烷(PDMS)为芯片主要材料,制作了PDMS—PDMS,PDMS—玻璃及PCB—PDMS三种芯片。制作的芯片能够在单个动力源条件下控制聚焦流宽度,使不同大小的微粒及细胞呈单个排列流动。研究结果为分析不同尺寸的细胞而选择合适的样品流沟道与鞘流沟道长度、夹角等条件提供了依据,所制作的芯片也达到了廉价且实用的目的。     

聚二甲基硅氧烷微流控芯片的制备

采用印刷电路板技术加工出芯片模具,以聚二甲基硅氧烷(PDMS)为材料制作出微流控芯片。该芯片由基片和盖片组成,微流控沟道位于基片上,深度和宽度分别为75μm和100μm,由盖片对其进行密封。考察了有绝缘漆模具和无绝缘漆模具制作的芯片的电泳分离情况。在该PDMS微流控芯片上对用异硫氰酸酯荧光素标记的氨基酸进行了电泳分离,当信噪比S/N=3时,最小检测浓度达到0.8×10-11mol/L。     

3D-printed peristaltic microfluidic systems fabricated from thermoplastic elastomer

Recent advancements in 3D printing technology have provided a potential low-cost and time-saving alternative to conventional PDMS (polydimethylsiloxane)-based microfabrication for microfluidic systems. In addition to reducing the complexity of the fabrication procedure by eliminating such intermediate steps as molding and bonding, 3D printing also offers more flexibility in terms of structural design than the PDMS micromolding process. At present, 3D-printed microfluidic systems typically utilize a relatively ‘stiff’ printing material such as ABS (acrylonitrile butadiene styrene copolymers), which limits the implementation of large mechanical actuation for active pumping and mixing as routinely carried out in a PDMS system. In this paper, we report the development of an active 3D-printed microfluidic system with moving parts fabricated from a flexible thermoplastic elastomer (TPE). The 3D-printed microfluidic system consists of two pneumatically actuated micropumps and one micromixer. The completed system was successfully applied to the detection of low-level insulin concentration using a chemiluminescence immunoassay, and the test result compares favorably with a similarly designed PDMS microfluidic system. Prior to system fabrication and testing, the material properties of TPE were extensively evaluated. The result indicated that TPE is compatible with biological materials and its 3D-printed surface is hydrophilic as opposed to hydrophobic for a molded PDMS surface. The Young’s modulus of TPE is measured to be 16 MPa, which is approximately eight times higher than that of PDMS, but over one hundred times lower than that of ABS.     

Enhancement of the surface free energy of PDMS for reversible and leakage-free bonding of PDMS–PS microfluidic cell-culture systems

Polydimethylsiloxane (PDMS) has become one of the most widely used materials in the fabrication of microfluidic systems bonded onto glass substrates, especially for cell biology applications. However, PDMS is often unsuitable for building microfluidic systems onto polystyrene (PS) which is the preferred substrate in most cell-culture protocols. In particular, PS is required for culturing many stem cell and primary cell types. Here, we propose a novel approach to building PDMS–PS microfluidic cell-culture systems, specifically realizing a strong and reversible bonding of PDMS on PS without using chemical agents which can have negative effects on cell viability. Our strategy to strengthen the bonding of PDMS to PS surfaces is to increase the surface free energy (SFE) by adjusting the mixing ratio of PDMS base to curing agent and by treating the surfaces of PDMS and PS with O₂ plasma and annealing. Our results show that using this method for PDMS–PS bonding, we are able to produce reliable reversible and leakage-free PDMS–PS microfluidic cell-culture systems.     

In-situ fabrication of an out-of-plane microlens with pre-definable focal length

Out-of-plane microlenses are an important component for integrated optics. Unlike their in-plane counterparts, the fabrication of out-of-plane microlenses is more complicated, which limits their applications. In this paper, a new technique that is capable of fabricating out-of-plane microlenses is described. The resulting lenses have pre-definable focal length and can focus light beams not only in the horizontal plane, but also in the vertical plane. The fabrication process is completely compatible with the soft lithography technique. The lens chamber with two thin polydimethylsiloxane (PDMS) membranes was designed and fabricated together with microfluidic or other components using the same UV lithography mask. The lens was then formed in an in-situ fashion. Curable polymers were injected into the lens chamber and cured while pneumatic pressure was applied to keep the PDMS membranes deformed in a quasi-spherical profile. Pneumatic pressure and membrane thickness can be adjusted to control the resulting lens focal length. With a group of lens chambers with different membrane thickness, a single pressure line can be used to fabricate microlenses with different focal lengths. Since cured polymer was used as the lens filling material, the resulting lens can be used without a pressure source. Different polymers can be selected for desirable optical properties. The simulation and experimental results have proved the feasibility of this technique and resulting lens showed good focusing ability for a divergent light beam from an on-chip multi-mode optical fiber. The small design footprint, total compatibility with soft lithography and technical versatility of this technique make it particularly useful for intergrating out-of-plane microlens into microfluidic chips, which may open new possibilities for the development of on-chip optical detection system.     

Printing 3D microfluidic chips with a 3D sugar printer

This study demonstrated how to quickly and effectively print two-dimensional (2D) and three-dimensional (3D) microfluidic chips with a low-cost 3D sugar printer. The sugar printer was modified from a desktop 3D printer by redesigning the extruder, so the melting sugar could be extruded with pneumatic driving. Sacrificial sugar lines were first printed on a base layer followed by casting polydimethylsiloxane (PDMS) onto the layer and repeating. Microchannels were then printed in the PDMS solvent, microfluidic chips dropped into hot water to dissolve the sugar lines after the PDMS was solidified, and the microfluidic chips did not need further sealing. Different types of sugar utilized for printing material were studied with results indicating that maltitol exhibited a stable flow property compared with other sugars such as caramel or sucrose. Low cost is a significant advantage of this type of sugar printer as the machine may be purchased for only approximately $800. Additionally, as demonstrated in this study, the printed 3D microfluidic chip is a useful tool utilized for cell culture, thus proving the 3D printer is a powerful tool for medical/biological research.