自制玻璃微流控芯片及其基本性能考察

20世纪90年代初,自Manz等首次提出微全分析系统的概念以来,各种不同材料和功能的微流控芯片不断问世,其中应用得最多的是玻璃、石英及聚合物3种材料．玻璃和石英芯片因具有优异的电渗、光学和表面性质,其刻蚀加工技术和表面改性的化学方法均比较成熟,且传统毛细管电泳中各种成熟的分离方法可直接应用到玻璃芯片的制作中,因此在微全分析系统研究中具有十分重要的地位．     

A method for UV-bonding in the fabrication of glass electrophoretic microchips.

This paper presents an approach for the development of methodologies amenable to simple and inexpensive microchip fabrication, potentially applicable to dissimilar materials bonding and chip integration. The method involves a UV-curable glue that can be used for glass microchip fabrication bonding at room temperature. This involves nothing more than fabrication of glue "guide channels" into the microchip architecture that upon exposure to the appropriate UV light source, bonds the etched plate and cover plate together. The microchip performance was verified by capillary zone electrophoresis (CZE) of small fluorescent molecules with no microchannel surface modification carried out, as well as with a DNA fragment separation following surface modification. The performance of these UV-bonded electrophoretic microchips indicates that this method may provide an alternative to high temperature bonding.     

Fabrication of SU-8 based microchip electrophoresis with integrated electrochemical detection for neurotransmitters

A new SU-8 based microchip capillary electrophoresis (MCE) device has been developed for the first time with integrated electrochemical detection. Embedded electrophoretic microchannels have been fabricated with a multilayer technology based on bonding and releasing steps of stacked SU-8 films. This technology has allowed the monolithic integration in the device of the electrochemical detection system based on platinum electrodes. The fabrication of the chips presented in this work is totally compatible with reel-to-reel techniques, which guarantee a low cost and high reliability production. The influence of relevant experimental variables, such as the separation voltage and detection potential, has been studied on the SU-8 microchip with an attractive analytical performance. Thus, the effective electrical isolation of the end-channel amperometric detector has been also demonstrated. The good performance of the SU-8 device has been proven for separation and detection of the neurotransmitters, dopamine (DA) and epinephrine (EP). High efficiency (30,000-80,000 N/m), excellent precision, good detection limit (450 nM) and resolution (0.90-1.30) has been achieved on the SU-8 microchip. These SU-8 devices have shown a better performance than commercial Topas (thermoplastic olefin polymer of amorphous structure) microchips. The low cost and versatile SU-8 microchip with integrated platinum film electrochemical detector holds great promise for high-volume production of disposable microfluidic analytical devices.     

Poly(ethylene glycol)-coated microfluidic devices for chip electrophoresis

Herein, we report on a strategy for durable modification of the channel surface in microfluidic glass chips with the neutral hydrophilic-coating material poly(ethylene glycol) PEG-1M-100. Applied in microchip electrophoresis such PEG-coated devices exhibit a suppressed electroosmotic flow and reduced analyte adsorption. The PEG-coated chips were successfully applied in chip electrophoresis of FITC-labelled amines and amino acids and native proteins as well as in chiral separations. The performance of the coated chips was found to be superior compared with uncoated microchips. The coated chips exhibited high stability and the relative standard deviation of migration times in PEG-coated devices was less than 2%.     

一种可逆键合电泳微芯片的制作及在蛋白质分离中的应用

阐述了一种可逆键合电泳微芯片的制作方法, 以及电泳微芯片在蛋白质分离、临床尿蛋白检测方面的应用. 用标准光刻腐蚀技术在石英基片上腐蚀泳道, 清洗腐蚀好的基片和盖片后, 在真空条件下实现键合. 此种方法键合制作的电泳微芯片可重复键合使用, 制得的电泳微芯片成功地用于标准蛋白质分离以及临床尿蛋白分析.     

Effects of peak anomalies with the hydrophilic or hydrophobic properties of reservoirs during serial injection on a capillary electrophoresis microchip

Several anomalies, e.g., in peak shape, migration time, and baseline drift, all due to pressure-driven backflow, were previously reported to occur during serial injection on capillary electrophoresis (CE) chips. Since these anomalies were worse for polydimethylsiloxane (PDMS) microchips than for glass microchips, reproducible data on PDMS microchips were difficult to obtain. In this paper, we found that these problems were affected by the hydrophilic or hydrophobic properties of the reservoirs on the microchip and demonstrated that these anomalies were reduced by converting the hydrophobic properties of the reservoirs on the PDMS microchip into hydrophilic ones. Thus, compared with hydrophobic reservoirs, hydrophilic reservoirs were suitable for the formation of a stable plug. Several chip designs were suggested to reduce these pressure-driven backflows.     

Integration of gene amplification and capillary gel electrophoresis on a polydimethylsiloxane-glass hybrid microchip

We report on the development of a hybrid polydimethylsiloxane (PDMS)-glass microchip for genetic analysis by functional integration of polymerase chain reaction (PCR) and capillary gel electrophoresis (CGE), and on related temperature control systems for PCR on a PDMS-glass hybrid microchip. The microchip was produced by molding PDMS against a microfabricated master with comparatively simple and inexpensive methods. PCR was successfully carried out on the PDMS-glass hybrid microchip with 500 bp target of lambdaDNA and the amplified gene was subsequently analyzed by CGE on the same PDMS-glass microchip. The chip could be considered as an inexpensive single-use apparatus compared to glass or silicon-made microchips for the same purpose.     

Wall coating for capillary electrophoresis on microchips

This review article with 116 references describes recent developments in the preparation of wall coatings for capillary electrophoresis (CE) on a microchip. It deals with both dynamic and permanent coatings and concentrates on the most frequently used microchip materials including glass, poly(methyl methacrylate), poly(dimethyl siloxane), polycarbonate, and poly(ethylene terephthalate glycol). Characterization of the channel surface by measuring electroosmotic mobility and water contact angle of the surface is included as well. The utility of the microchips with coated channels is demonstrated by examples of CE separations on these chips.     

Bulk modification of polymeric microfluidic devices

The surface properties of microfluidic devices play an important role in their flow behavior. We report here on an effective control of the surface chemistry and performance of polymeric microchips through a bulk modification route during the fabrication process. The new protocol is based on modification of the bulk microchip material by tailored copolymerization of monomers during atmospheric-pressure molding. A judicious addition of a modifier to the primary monomer solution thus imparts attractive properties to the plastic microchip substrate, including significant enhancement and/or modulation of the EOF (with flow velocities comparable to those of glass), a strong pH sensitivity and high stability. Carboxy, sulfo, and amino moieties have thus been introduced (through the incorporation of methylacrylic acid, 2-sulfoethyl-methacrylate and 2-aminoethyl-methacrylate monomers, respectively). A strong increase in the electroosmotic pumping compared to the native poly(methylmethacrylate)(PMMA) microchip (ca. electroosmotic mobility increases from 2.12 to 4.30 x 10(-4) cm(2) V(-1) s(-1)) is observed using a 6% methylacrylate (MAA) modified PMMA microchip. A 3% aminoethyl modified PMMA microchip exhibits a reversal of the electroosmotic mobility (for example, -5.6 x 10(-4) cm(2) V(-1) s(-1) at pH 3.0). The effects of the modifier loading and the pH on the EOF have been investigated for the MAA-modified PMMA chips. The bulk-modified devices exhibit reproducible and stable EOF behavior. The one step fabrication/modification protocol should further facilitate the widespread production of high-performance plastic microchip devices.     

Chemical modification of polymeric microchip devices

Analytical polymeric microchips in both fluidic and array formats offer short analysis times, coupling of many sample processing and chemical reaction steps on one platform with minimal sample and reagent consumption, as well as low cost, minimal fabrication times and disposability. However, the invariable bulk properties of most commercial polymers have driven researchers to develop new modification strategies. This article critically reviews the scope and development of chemical modifications of such polymeric chips since 2003. Surface modifications were based on chemical derivatization or activation of surface layers with reagent solutions, reactive gases and irradiation. Bulk modification of polymer chips used newly incorporation of monomers with selective chemical functionalities throughout the bulk polymer material and integrated the chip modification and fabrication into a single step. Such modifications hold a great promise for establishing a true ‘lab-on-chip’ as can be seen from many novel applications for modulating electroosmosis, suppressing protein adsorption in microchip capillary electrophoretic separations, extraction of analytes and for zone-specific binding of enzymes and other biomolecules.     

Microfluidic chips for biological and medical research

Advantages of devices on a microchip platform are discussed in comparison with traditional systems. Stages and processes of creation of microfluidic chips are considered. The basic technologies of formation micro- and nanostructures on a substrate from various materials and techniques for microchip sealing are introduced. Special attention is given to microfluidic chips for separation and analysis of nucleic acids and proteins, as well as to microchips for PCR. Examples of integrated systems on the basis of microfluidic technique are considered. Data on the commercialization of devices based on microfluidic chips are presented.     

Physiochemical properties of various polymer substrates and their effects on microchip electrophoresis performance

A suite of polymers were evaluated for their suitability as viable substrate materials for microchip electrophoresis applications, which were fabricated via replication technology. The relevant physiochemical properties investigated included the glass transition temperature (T(g)), UV-vis absorption properties, autofluorescence levels, electroosmotic flow (EOF) and hydrophobicity/hydrophilicity as determined by sessile water contact angle measurements. These physiochemical properties were used as a guide to select the proper substrate material for the intended microchip electrophoretic application. The T(g) of these polymers provided a guide for optimizing embossing parameters to minimize replication errors (REs), which were evaluated from surface profilometer traces. RE values ranged from 0.4 to 13.6% for the polymers polycarbonate (PC) and low-density polyethylene (LDPE), respectively. The absorption spectra and autofluorescence levels of the polymers were also measured at several different wavelengths. In terms of optical clarity (low absorption losses and small autofluorescence levels), poly(methyl methacrylate), PMMA (clear acrylic), provided ideal characteristics with autofluorescence levels comparable to glass at excitation wavelengths that ranged from 488-780 nm. Contact angle measurements showed a maximum (i.e., high degree of hydrophobicity) for polypropylene (PP), with an average contact angle of 104 degrees +/-3 degrees and a minimum exhibited by gray acrylic, G-PMMA, with an average contact angle of 27 degrees +/-2 degrees. The EOF was also measured for thermally assembled chips both before and after treatment with bovine serum albumin (BSA). The electrophoretic separation of a mixture of dye-labeled proteins including; carbonic anhydrase, phosphorylase B, beta-galactosidase, and myosin, was performed on four different polymer microchips using laser-induced fluorescence (LIF) excitation at 632.8 nm. A maximum average resolution of 5.04 for several peak pairs was found with an efficiency of 6.68 x 10(4) plates for myosin obtained using a BSA-treated PETG microchip.     

Development of monolithic enzymatic reactors in glass microchips for the quantitative determination of enzyme substrates using the example of glucose determination via immobilized glucose oxidase

A one-step procedure for the immobilization of glucose oxidase in fused-silica capillaries and in glass microchips was developed based on enzyme entrapment in a polyacrylamide-based monolithic column. The inner capillary surface was silanized with gamma-methacryloxypropyltrimethoxysilane (gamma-MAPS) to allow covalent binding of the gel to the surface. The composition of the polymer was optimized to prevent the formation of bubbles, allow liquid transportation by electroosmotic flow and to maintain the enzymatic activity. These requirements resulted in the addition of polyethylene glycol and poly(acrylic acid) to the acrylamide mixture. The gel containing the enzyme was formed in situ in the capillaries, respectively, in one channel of the microchip. In the microchip, it was limited to the sample injection channel by accordingly controlled silanization of the inner capillary surface. Glucose was detected via the amperometric determination of hydrogen peroxide. A linear correlation between signals and glucose concentration was observed from 0.05 to 1.1 mM glucose with a correlation coefficient of 0.999. The enzymatic monolithic microreactor showed no loss of activity during 8 h of continuous use and during storage in the running buffer at 4 degrees C for about 2 months. Interferents, such as ascorbic acid, were separated from the analyte electrophoretically, so that glucose could be quantified in diluted juices.     

CE microchips: an opened gate to food analysis

CE microchips are the first generation of micrototal analysis systems (-TAS) emerging in the miniaturization scene of food analysis. CE microchips for food analysis are fabricated in both glass and polymer materials, such as PDMS and poly(methyl methacrylate) (PMMA), and use simple layouts of simple and double T crosses. Nowadays, the detection route preferred is electrochemical in both, amperometry and conductivity modes, using end-channel and contactless configurations, respectively. Food applications using CE microchips are now emerging since food samples present complex matrices, the selectivity being a very important challenge because the total integration of analytical steps into microchip format is very difficult. As a consequence, the first contributions that have recently appeared in the relevant literature are based primarily on fast separations of analytes of high food significance. These protocols are combined with different strategies to achieve selectivity using a suitable nonextensive sample preparation and/or strategically choosing detection routes. Polyphenolic compounds, amino acids, preservatives, and organic and inorganic ions have been studied using CE microchips. Thus, new and exciting future expectations arise in the domain of food analysis. However, several drawbacks could easily be found and assumed within the miniaturization map.     

A rigid poly(dimethylsiloxane) sandwich electrophoresis microchip based on thin-casting method

We present a novel concept of glass/poly(dimethylsiloxane) (PDMS)/glass sandwich microchip and developed a thin-casting method for fabrication. Unlike the previously reported casting method for fabricating PDMS microchip, several drops of PDMS prepolymer were first added on the silanizing SU-8 master, then another glass plate was placed over the prepolymer as a cover plate, and formed a glass plate/PDMS prepolymer/SU-8 master sandwich mode. In order to form a thin PDMS membrane, a weight was placed on the glass plate. After the whole sandwich mode was cured at 80 degrees C for 30 min, the SU-8 master was easily peeled and the master microstructures were completely transferred to the PDMS membrane which was tightly stuck to the glass plate. The microchip was subsequently assembled by reversible sealing with the glass cover plate. We found that this PDMS sandwich microchip using the thin-casting method could withstand internal pressures of >150 kPa, more than 5 times higher than that of the PDMS hybrid microchip with reversible sealing. In addition, it shows an excellent heat-dissipating property and provides a user-friendly rigid interface just like a glass microchip, which facilitates manipulation of the microchip and fix tubing. As an application, PDMS sandwich microchips were tested in the capillary electrophoresis separation of fluorescein isothiocyanate-labeled amino acids.     

Versatile method for electroosmotic flow measurements in microchip electrophoresis

A novel versatile method for the determination of low or high electroosmotic mobility values in microdevices of variable microchannel design is presented. The electroosmotic flow (EOF) calculation is based on the difference between the apparent and effective mobilities of a reference compound. The proposed method uses microchip frontal electrophoresis for the determination of these mobilities. This requires simple monochannel microchip design and demonstrates versatile and time-saving procedure when compared to conventional current monitoring method when measuring low EOF. It has been applied successfully to the characterization of different coating procedure in glass and poly(dimethylsiloxane) microchips.     

Integration of chemical and biochemical analysis systems into a glass microchip.

This review focuses on the integration of chemical and biochemical analysis systems into glass microchips for general use. By combining multiphase laminar flow driven by pressure and micro unit operations, such as mixing, reaction, extraction and separation, continuous-flow chemical processing systems can be realized in the microchip format, while the application of electrophoresis-based chip technology is limited. The performances of several analysis systems were greatly improved by microchip integration because of some characteristics of microspace, i.e., a large specific interface area, a short molecular diffusion time, a small heat capacity and so on. By applying these concepts, several different analysis systems, i.e., wet analysis of cobalt ion, multi-ion sensor, immunoassay, and cellular analysis, were successfully integrated on a microchip. These microchip technologies are promising for meeting the future demands of high-throughput chemical processing.     

Characterization and performance of injection molded poly(methylmethacrylate) microchips for capillary electrophoresis

Injection molded poly(methylmethacrylate) (IM-PMMA), chips were evaluated as potential candidates for capillary electrophoresis disposable chip applications. Mass production and usage of plastic microchips depends on chip-to-chip reproducibility and on analysis accuracy. Several important properties of IM-PMMA chips were considered: fabrication quality evaluated by environmental scanning electron microscope imaging, surface quality measurements, selected thermal/electrical properties as indicated by measurement of the current versus applied voltage (I-V) characteristic and the influence of channel surface treatments. Electroosmotic flow was also evaluated for untreated and O2 reactive ion etching (RIE) treated surface microchips. The performance characteristics of single lane plastic microchip capillary electrophoresis (MCE) separations were evaluated using a mixture of two dyes-fluorescein (FL) and fluorescein isothiocyanate (FITC). To overcome non-wettability of the native IM-PMMA surface, a modifier, polyethylene oxide was added to the buffer as a dynamic coating. Chip performance reproducibility was studied for chips with and without surface modification via the process of RIE with O2 and by varying the hole position for the reservoir in the cover plate or on the pattern side of the chip. Additionally, the importance of reconditioning steps to achieve optimal performance reproducibility was also examined. It was found that more reproducible quantitative results were obtained when normalized values of migration time, peak area and peak height of FL and FITC were used instead of actual measured parameters.     

Recent innovations in protein separation on microchips by electrophoretic methods

Microchips for analytical purposes have attracted great attention over the last 20 years. In the present review, we focus on the most recent development of microchips for electrophoretic separation of proteins. This review starts with a short recalling about the microchips covering the basic microchip layout for CE and the commercial chips and microchip platforms. A short paragraph is dedicated to the surface treatment of microchips, which is of paramount importance in protein analysis. One section is dedicated to on-line sample pretreatment in microchips and summarizes different strategies to pre-concentrate or to purify proteins from complex matrixes. Most of the common modes used for CE of proteins have already been adapted to the chip format, while multidimensional approaches are still in progress. The different routes to achieve detection in microchip are also presented with a special attention to derivatization or labeling of proteins. Finally, several recent applications are mentioned. They highlight the great potential of electrophoretic separations of proteins in numerous fields such as biological, pharmaceutical or agricultural and food analysis. A bibliography with 151 references is provided covering papers published from 2000 to the early 2007.