中国微米纳米-微纳结构对电容式柔性压力传感器性能影响的研究

设计制备出三明治结构的电容式柔性压力传感器,并对其性能进行研究.该传感器以银纳米线为电极材料,聚二甲基硅氧烷(PDMS)为柔性衬底,同时采用毛面玻璃和光面玻璃分别作为柔性衬底的制备模板,制备出微纳结构和平面结构的PDMS薄膜.然后采用喷涂法制备AgNWs/PDMS复合电极,以另外一层PDMS为介电层,将两电极面对面封装,得到电容式柔性压力传感器,最后系统研究了传感器的电极微纳结构对器件性能的影响.本文研究表明,具有微纳结构的AgNWs/PDMS复合薄膜传感器的灵敏度为1.0 kPa-1,而平面结构的AgNWs/PDMS复合薄膜传感器的灵敏度为0.6 kPa-1,由此可知具有微纳结构的柔性衬底能够显著提高器件的灵敏度.     

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。     

玻璃-PDMS薄膜-玻璃夹心微流控芯片制作

聚二甲基硅氧烷(PDMS)是目前微流控芯片中应用的最广泛的基质材料,但基于PDMS材料的微流控芯片在应用中存在溶剂易挥发、难以进行较长时间检测分析的问题.针对这些问题,发展了一种简便高效的“玻璃-PDMS薄膜-玻璃”(G-P-G)夹心式微流控芯片的制作方法.该方法巧妙利用聚酯(PET)胶片作为载体转移处理脆弱的结构化PDMS膜,然后通过等离子体处理将结构化PDMS膜夹在两个玻璃基板的中间,形成“玻璃-PDMS薄膜-玻璃”夹心结构芯片,由于玻璃材料的低通透性,使得芯片具有低溶剂挥发特性.该夹心式芯片的低溶剂挥发特性通过蛋白质结晶实验得到了验证.     

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。     

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.     

复合式微流控脱水芯片的研制

报道了一种复合式微流控脱水芯片。采用玻璃、聚二甲氧基硅氧烷(PDMS)和聚碳酸酯(PC)三种材质,采用不可逆封接方法分别制得玻璃—PDMS液路半芯片、PC—PDMS气路半芯片,中间夹一层聚四氟乙烯(PTFE)多孔滤膜,将两个半芯片可逆封接形成玻璃—PDMS…PDMS—PC结构的全芯片。该制备方法简单可靠,其液路半芯片和气路半芯片可以单独更换,使得使用成本降低。实验表明:该芯片脱水性能良好,可用于有机合成步骤中含水试剂的高效除水。     

PDMS用加窗方式快速复制微结构

提出了一种微流控芯片中的制作方法,此方法可以复制现有芯片的任意结构,可用于实验室原有芯片的修复和整合.用窗口的方法提取结构,可排除芯片上相邻结构的干扰,得到表面光滑整齐的新芯片.特别适用于复制目前软光刻工艺尚未达到的特微结构和三维结构芯片.实验制作出的聚二甲基硅氧烷(PDMS)芯片沟道长30μm,宽5μm,深5μm,显微镜下观察芯片表面光滑,窗口内沟道性质复制良好,窗口边缘与表面之间具有明显的陡变.     

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。     

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。     

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.     

Nickel stamp fabrication and hot embossing for mass-production of micro/nano combined structures using anodic aluminum oxide

Recently, “micro/nano combined structure” has attracted many researchers’ attentions due to its high potential in various research fields and applications such as biomimetics, tissue engineering, micro systems for biochemical analysis and so forth. The present paper proposes a simple and promising method for mass-production of the micro/nano combined structure, in particular, nano dimple array with micro structures with cost-effective procedures. Three major procedures of (a) master template fabrication; (b) nickel electroforming onto the master template; (c) replication by hot embossing process, are employed: the master template is fabricated by utilizing an anodic aluminium oxide (AAO) process and UV lithography technique; nickel stamp is then obtained by means of electroforming onto the master template; finally, micro/nano combined structures are moulded on a polymethyl methacrylate (PMMA) substrate using the nickel stamp via hot embossing. So replicated micro/nano combined structures turns out to be quite successful according to experimental observation via scanning electron microscope (SEM) and atomic force microscope (AFM).     

A highly reliable integrated PDMS interconnector with a long cast flange for microfluidic systems

This paper presents a highly reliable macro to micro domain interconnection technology for microfluidic applications using Polydimethylsiloxane (PDMS) casting techniques. Characteristic to the interconnectors are long flanges fabricated in the PDMS film; therefore the contact area between PDMS and tubes is considerably increased compared to other interconnection technologies. Thus, both glass capillaries and Polytetrafluoroethylene (PTFE) tubes can be held in position very reliably and rigidly. To test the reliability of the interconnectors, PTFE tubes were successfully connected to microfluidic chips without the aid of any liquid adhesives. Both leakage and pull-out tests demonstrated the functionality and reliability of the PDMS interconnectors; no leakage was detected under a working pressure up to 400?kPa. A pull-out test yielded a pull-out force of 22.45?N. Furthermore, once a casting mould is fabricated, it can be re-used as a template repeatedly achieving a low cost technology and making it suitable for batch production.     

Design and modeling of electromagnetic actuator in mems-based valveless impedance pump

This study models and optimizes the electromagnetic actuator in an MEMS-based valveless impedance pump. The actuator comprises an electroplated permanent magnet mounted on a flexible PDMS diaphragm and electroplated Cu coils located on a glass substrate. In optimizing the design of the actuator, the objective is to maximize the output flow rate of the micropump while maintaining the mechanical integrity of its constituent parts. The study commences by developing optimized theoretical models for each of the components within the actuator, namely the diaphragm, the magnet, and the micro-coils. The theoretical models are then verified numerically using FEA software. The magnitude of the magnetic force acting on the flexible diaphragm is calculated using Ansoft/Maxwell3D FEA software. The simulation results obtained by ANSYS FEA software for the diaphragm deflection are found to be in good agreement with the theoretical predictions. In general, the results show that the desired diaphragm deflection of 15 μm can be obtained by passing a current of 0.6–0.7 A through the micro-coil to produce a compression force of 11 μN. The valveless micro impedance pump proposed in this study is easily fabricated and is readily integrated with existing biomedical chips due to its plane structure. The results of this study provide a valuable contribution to the ongoing development of Lab-on-a Chip systems.     

Development of an ultrafast quantitative heterogeneous immunoassay on pre-functionalized poly(dimethylsiloxane) microfluidic chips for the next-generation immunosensors

Although the reaction time for antigen-antibody binding has been greatly reduced in microchannels, other processes in heterogeneous immunoassays (HEIs), such as blocking and antigen adsorption have not benefited from miniaturization as a reduction in size to micro dimensions does not increase the speed of these processes significantly. The overall assay time of reported microfluidic HEIs has continued to be limited by these processes. In this study, we successfully develop an ultrafast quantitative HEI with pre-functionalized microfluidic poly(dimethylsiloxane) (PDMS) chips. The protein A functionalized PDMS surface is found to be highly effective in reducing the antigen adsorption time in microchannels. The functionalized surfaces can be stable at least for 2.5 months when stored at 4°C in a buffer solution consisting of 10 mM Tris, 0.05% bovine serum albumin, 0.05% Proclin 300, and 5% glycerol. In addition, the immunosorption process, which is substantially accelerated in micro scale, results in a significant reduction in nonspecific binding. The time of blocking step can therefore be reduced to a minimum or can be eliminated. The overall assay for detecting bovine immunoglobulin G is completed in 19 min with a limit of detection of 3.8 nM. The ultrafast analysis time and superior sensitivity demonstrated by this microfluidic HEI is promising for being used to develop the next-generation immunosensors.     

New Architecture of a Hybrid Two-Fingered Micro–Nano Manipulator Hand: Optimization and Design

This paper presents the synthesis and design optimization of a compact and yet economical hybrid two-fingered micro–nano manipulator hand. The proposed manipulator hand consists of two series modules, i.e., an upper and lower modules. Each of them consists of a parallel kinematics chain with a glass pipette (1 mm diameter and 3–10 cm length) tapered to a very sharp end as an end-effector. It is driven by three piezo-electric actuated prismatic joints in each of the three legs of the parallel kinematics chain. Each leg of the kinematics chain has the prismatic–revolute–spherical joint structure. As the length of the glass pipette end-effector is decreased, the resolution and accuracy of the micro–nano manipulator hand is increased. For long lengths of the glass pipette end-effector, this manipulator works as a micro manipulator and for short lengths it works as a nano manipulator. A novel closed-form solution for the problem of inverse kinematics is obtained. Based on this solution, a simulation program has been developed to optimally choose the design parameters of each module so that the manipulator will have a maximum workspace volume. A computer-aided design model based on optimal parameters is built and investigated to check its workspace volume. Experimental work has been carried out for the purpose of calibration. Also, the system hardware setup of the hybrid two-fingered micro–nano manipulator hand and its practical Jacobian inverse matrices are presented.     

Site-directed antibody immobilization on gold substrate for surface plasmon resonance sensors

A simple method for the site-directed immobilization of antibodies on gold substrates has been developed for surface plasmon resonance (SPR) applications. A freshly prepared gold surface on a glass slide was modified with Protein A via homobifunctional cross linker dithiobissuccinimide propionate (DSP) to achieve uniform, stable, and sterically accessible antibody coating. The density of the immobilized antibodies bound to Protein A was examined as a function of the protein concentration, buffer pH, buffer type and reaction time. The suggested scheme was also employed for the modification of gold-coated substrates for quartz crystal microbalance (QCM) applications. The modified gold surface was stable for several weeks and the reproducibility was satisfactory. The current fabrication technique could be applied to construct other immunosensors or biochips.     

Dependence of the quality of adhesion between poly(dimethylsiloxane) and glass surfaces on the composition of the oxidizing plasma

Controlled surface oxidation of polydimethylsiloxane (PDMS) is essential for permanent adhesion between device components composed of this elastomer. The permanent adhesion between such microdevice components results from covalent crosslinking across the interfaces between PDMS and other silica-based materials, such as glass, quartz, and PDMS. Optimal duration and conditions of oxidation, attained via treatments with oxygen-containing plasma, are crucial for microfabrication procedures with quantitative yields. While insufficient PDMS oxidation does not provide high enough surface density of siloxyl groups for cross-interface linking, overoxidation of PDMS yields rough silica surface layers that prevent the adhesion between flat substrates. Ideally, for a set of plasma conditions, the range of treatment durations producing permanent adhesion should be as broad as possible: i.e., the surface oxidation of PDMS sufficient for irreversible binding has to complete significantly before the effects of overoxidation become apparent. Such a requirement assures that relatively small fluctuations in the treatment conditions will not result in over- or under-oxidation and, hence, will not compromise the yields of the fabrication procedures. We examined the dependence of the quality of adhesion (QA) between plasma-treated PDMS and glass substrates on the composition of the oxygen-containing plasma and on the radio frequency (RF) of the plasma generator. We observed that plasma generated at megahertz RF provided superior conditions than kilohertz RF. Concurrently, an increase in the oxygen content of binary gas mixtures, used for the plasma, broadened the treatment durations that afford superior QA.     

Miniaturized plastic micro plates for applications in HTS

This paper is focused on the development of plastic nano titer plates for applications in high throughput screening (HTS). For screening systems with integrated confocal microscopes plastic chips have been fabricated by injection molding and injection compression molding which contain micro wells with volumes of 0.9 μl and 1.4 μl and bottom plates with thicknesses of 120 μm and 200 μm. In addition, plastic chips with through holes have been joined with 160 μm glass plates by an adhesive printing process. First fluorescence correlation spectroscopy (FCS) measurements show that the plastic plates with glass bottoms are qualified as screening grade FCS nano titer plates. Received: 15 May 1999 / Accepted: 19 May 1999     

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.     

Solvent-free surface modification by initiated chemical vapor deposition to render plasma bonding capabilities to surfaces

A versatile solvent-free method for surface modification of various materials including both metals and polymers is described. Strong irreversible bonds were formed when substrates modified by initiated chemical vapor deposition (iCVD) of poly(1,3,5-trivinyltrimethylcyclotrisiloxane) or poly(V3D3) and exposed to an oxygen plasma were brought into contact with plasma-treated poly(dimethylsiloxane) (PDMS). The strength of these bonds was quantified by burst pressure testing microfluidic channels in the PDMS. The burst pressures of PDMS bonded to various coated substrates were in some cases comparable to that of PDMS bonded directly to PDMS. In addition, porous PTFE membrane coated with poly(V3D3) was successfully bonded to a PDMS microfluidic device and withstood pressures of over 300 mmHg. Bond strength was shown to correlate with surface roughness and quality of the bond between the coating and substrate. This work paves a methodology to fabricate microfluidic devices that include a specifically tailored membrane. Furthermore, the bonded devices exhibited hydrolytic stability; no dramatic change was observed even after immersion in water at room temperature over a period of 10 days.