低成本聚合物微流控芯片加工技术综述

针对传统微流控芯片加工方法成本高昂、耗时长的问题,近年来出现了多种低成本的微流控芯片加工方法,在聚合物、纸等材料上加工、完成了能够满足其应用需求的微流控芯片。对当前各类基于聚合材料的低成本微流控芯片加工技术进行了梳理和总结,并对未来低成本微流控芯片的发展进行了展望。     

Fast fabrication of microfluidic devices using a low-cost prototyping method

Conventional ways to produce microfluidic devices cost a lot due to the requirements for cleanroom environments and expensive equipment, which prevents the wider applications of microfluidics in academia and in industry. In this paper, a dry film photoresist was utilized in a simple way to reduce the fabrication cost of microfluidic masters. Thus, a fast prototyping and fabrication of microstructures in polydimethylsiloxane microchips through a replica molding technology was achieved in a low-cost setting within 2.5 h. Subsequently, major manufacturing conditions were optimized to acquire well-resolved microfluidic molds, and the replicated microchips were validated to be of good performance. A T-junction channel microchip was fabricated by using a dry film master to generate water droplets of uniform target size. Meanwhile, a gated injection of fluorescein sodium and a contactless conductivity detection of Na⁺ were both performed in a crosslink channel microchip via capillary electrophoresis, in other words, this fast prototyping and fabrication method would be an efficient, economical way to embody structural design into microfluidic chips for various applications.     

Simulation and verification of polydimethylsiloxane (PDMS) channels on acoustic microfluidic devices

Microsystem Technologies - Polydimethylsiloxane (PDMS) is widely used as a channel material in microfluidic applications. Due to its highly elastomeric characteristics, PDMS absorbs the acoustic...     

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。     

Fabrication of PDMS microfluidic chips used in rapid diagnosis by micro jetting

Multimedia Tools and Applications - In this paper, a simple method was demonstrated to fabricate polydimethylsiloxane (PDMS) microfluidic chips used in rapid diagnosis based on printing the liquid...     

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。     

Design and fabrication of a novel microfluidic nanoprobe

The design and fabrication of a novel microfluidic nanoprobe system are presented. The nanoprobe consists of cantilevered ultrasharp volcano-like tips, with microfluidic capabilities consisting of microchannels connected to an on-chip reservoir. The chip possesses additional connection capabilities to a remote reservoir. The fabrication uses standard surface micromachining techniques and materials. Bulk micromachining is employed for chip release. The microchannels are fabricated in silicon nitride by a new methodology, based on edge underetching of a sacrificial layer, bird's beak oxidation for mechanically closing the edges, and deposition of a sealing layer. The design and integration of various elements of the system and their fabrication are discussed. The system is conceived mainly to work as a "nanofountain pen", i.e., a continuously writing upgrade of the dip-pen nanolithography approach. Moreover, the new chip shows a much larger applicability area in fields such as electrochemical nanoprobes, nanoprobe-based etching, build-up tools for nanofabrication, or a probe for materials interactive analysis. Preliminary tests for writing and imaging with the new device were performed. These tests illustrate the capabilities of the new device and demonstrate possible directions for improvement.     

A novel approach to CNC machining center processing parameters optimization considering energy-saving and low-cost

NC machining is currently a machining method widely used in mechanical manufacturing systems. Reasonable selection of process parameters can significantly reduce the processing cost and energy consumption. In order to realize the energy-saving and low-cost of CNC machining, the cutting parameters are optimized from the aspects of energy-saving and low-cost, and a process parameter optimization method of CNC machining center that takes into account both energy-saving and low -cost is proposed. The energy flow characteristics of the machining center processing system are analyzed, considering the actual constraints of machine tool performance and tool life in the machining process, a multi-objective optimization model with milling speed, feed per tooth and spindle speed as optimization variables is established, and a weight coefficient is introduced to facilitate the solution to convert it into a single objective optimization model. In order to ensure the accuracy of the model solution, a combinatorial optimization algorithm based on particle swarm optimization and NSGA-II is proposed to solve the model. Finally, take plane milling as an example to verify the feasibility of this method. The experimental results show that the multi-objective optimization model is feasible and effective, and it can effectively help operators to balance the energy consumption and processing cost at the same time, so as to achieve the goal of energy conservation and low-cost. In addition, the combinatorial optimization algorithm is compared with the NSGA-II, the results show that the combinatorial optimization algorithm has better performance in solving speed and optimization accuracy.     

基于PDMS的微流量计的研制

通过检测透皮抽取出的人体细胞间液中葡萄糖浓度来预测血糖浓度是一种重要的微创血糖检测技术。但由于抽取出的细胞间液量很少,需要进行稀释以便输送和收集,然后根据稀释后的体积来计算稀释前的细胞间液浓度。设计和加工了一种微流量计用以测量稀释后细胞间液的体积,并搭建了性能测试实验平台,测试了流量计测量结果的重复性和线性相关性。实验表明:流量计测量范围为4～16μL;对15μL的样品10次测量的变异系数为6.2%;13个不同体积样品的测量结果相关系数为0.988。微流量计能够满足测量要求。     

Droplet coalescence by geometrically mediated flow in microfluidic channels

Microfluidic flow is geometrically mediated at a trifurcating junction allowing periodically formed, equally spaced out emulsion droplets to redistribute and fuse consistently. This is achieved by controlling the ratio between the droplet transport time across the trifurcating junction and the drainage time of the fluid volume separating the droplets t _r/t _d. Three different microfluidic trifurcation geometries have been designed and compared for their droplet fusion efficiencies. Fusion of up to six droplets has been observed in these devices. The fusion of two droplets occurs when t _r/t _d is equal to 1.25 and the number of fused droplets increases with t _r/t _d. When the junction length (d) is 216 μm fusion of 2–6 six droplets are possible however when the junction length is increased to 360 μm fusion of only two droplets is observed.     

Hermetic encapsulation of negative-pressure-driven PDMS microfluidic devices using paraffin wax and glass

Microsystem Technologies - This paper presents a new hermetic encapsulation method for negative-pressure-driven polydimethylsiloxane (PDMS) microfluidic devices. The hermetic materials used in this...     

微流控芯片的材料与加工方法研究进展

综述了微流控芯片的制作材料及其加工方法的研究进展.在介绍了传统硅质材料,如硅、玻璃、石英等的基础上,着重描述了高分子聚合物材料在微流控芯片的应用趋势.针对不同材料,详叙了其材料特性、应用范围及加工方法.特别介绍了一些新的加工方法,如激光刻蚀法、软光刻、LIGA方法在该领域的应用.针对微流控芯片的材料与加工做了一个简要而...     

Patterned paper and alternative materials as substrates for low-cost microfluidic diagnostics

In recent years a strong need has been realised for the creation of low-cost diagnostics for use in impoverished regions of the world. The use of paper has been championed for this purpose by many research groups globally over the past 5?years, leading to the formation of a large body of knowledge. This work reviews and summarises the many techniques developed to date for the patterning of paper substrates to create channels for the flow of liquids. The work also explores methods for increasing the functionality of paper-based microfluidics, the detection mechanisms employed so far and some of the interesting applications addressed. The review will also investigate the recent use of some alternative materials—both as primary substrates and in hybrids—which will become progressively more important in the future.     

Enhanced bioreaction efficiency of a microfluidic mixer toward high-throughput and low-cost bioassays

Microscale bioreactors are an important tool in performing bioassays. The speed and efficiency of these devices is often limited by the rate of reagent mixing. In spite of the various micromixing approaches, the coupled mixing/reaction process has yet to be clearly understood. This article presents experimental and computational studies on the enhancement of bioreaction rates using a novel cilia reactor. In the experiments, a biotin-avidin assay and a DNA hybridization assay were conducted to show the benefit of a cilia bioreactor compared with a simple diffusion reactor. A cilia reactor showed a shorter reaction time for approaching equilibrium. A numerical computation examined the bioreaction rate of the cilia reactor compared with the diffusion for (1) a biotin-avidin assay, (2) an immunoassay, and (3) a DNA hybridization assay. The reaction rate was characterized for each assay using the Damk?hler number (Da). When Da was greater than 10², the ratio of reaction time for the diffusion to cilia reactors linearly increased with Da, which could also save reagent usage by lowering the concentration of reagent probes. However, when the system had a Da smaller than 10², the reaction time of a cilia reactor could not be shortened because the assay was dominated by reaction rather than fluid mixing. The results offer a general approach for enhancing bioreaction rates by employing microfluidic mixers for a bioassay.     

Design of microfluidic channels separated by an ultra-thin free-standing dielectric membrane

A microfluidic (MF) surface plasmon polariton sensor featuring a gold Mach–Zehnder interferometer on an ultra-thin (20–35 nm) dielectric membrane is described. While the presence of the membrane is required to maintain a near mirror symmetry of the dielectric properties of the medium on either side of the interferometer, it is a source of unique challenges in the MF system design. The pressure required to drive the fluid flow in microchannels causes deflection whose value depends on the membrane’s residual stress in the low pressure range and on its modulus at the higher pressure range. Depending on the empirical membrane strength which would meet the required equipment reliability, narrow fluidic channels may require tight dimensional tolerances to maintain the pressure difference across the membrane below a critical value. With wider channels (≥100 μm) dimensional tolerances are relaxed even with relatively weak membranes.     

A low-cost method of fabricating hybrid micro-nano fluidic chip by double-layer PDMS mold and UV–thermal nanoimprinting

Micro-nano fluidic chips have become important tools in biomedical testing and research, their more frequent and diverse application being hampered mainly by their high cost, reflective of complex and expensive production methods. Our study introduces a simple, cost-effective new procedure whereby a sturdy PDMS mold consisting of two layers of poured PDMS with a photomask film bonded between them is used for replicating a hybrid micro-nano structure on a SU-8 substrate. The bottom surface of the mold receives a pattern of nano-ridges by pouring the first layer of PDMS on a 2D silicon nano-mold obtained by plasma etching after inclined Cu deposition. Using the double-layer PDMS mold, nano-channels can be imprinted with micro-channels cross-linked through the photomask in a single step of UV–thermal imprinting. The advantages of our end product, a chip with 205-μm-wide and 10-μm-deep micro-channels, cross-linked with 158-nm-wide and 90-nm-deep nano-channels, are its high precision and low cost.     

Liquid recirculation in microfluidic channels by the interplay of capillary and centrifugal forces

We demonstrate a technique to recirculate liquids in a microfluidic channel by alternating predominance of centrifugal and capillary forces to rapidly bring the entire volume of a liquid sample to within one diffusion length, δ, of the surface, even for sample volumes hundreds of times the product of δ and the geometric device area. This is accomplished by repetitive, random sampling of an on-disc sample reservoir to form a thin fluid layer of thickness δ in a microchannel, maintaining contact for the diffusion time, then rapidly exchanging the fluid layer for a fresh aliquot by disc rotation and stoppage. With this technique, liquid volumes of microlitres to millilitres can be handled in many sizes of microfluidic channels, provided the channel wall with greatest surface area is hydrophilic. We present a theoretical model describing the balance of centrifugal and capillary forces in the device and validate the model experimentally.     

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。