Microfluidic chips

Electroosmotic flow (EOE) is thus the mechanism by which liquids are moved from one end of the sepai ation capillai y to the other, obviating the need for mechanical pumps and valves. This makes this technique very amenable to miniaturization, as it is fai simpler to make an electrical contact to a chip via a wire immersed in a reservoir than to make a robust connection to a pump. More important, however, is that all the basic fluidic manipulations that a chemist requires for microchip electrophoresis, or any other liquid handling for that matter, have been adapted to electrokinetic microfluidic chips. 

In this work we discuss some bioanalytes such as amino acids assay by electrokinetic microfluidic chip with ECE detection. 

Fig. 2.6.5 Hardware for high field NMR remote probe in (c) contains a relatively large saddle-detection. Photographs (a) and (b) show la- coil and is used for (flow) imaging. The detec-boratory-built remote detection probes with tor probe in (d) contains a microsolenoid coil both rf coils built into the same body (c), (d) for optimized mass sensitivity, which is parti-and (e) are detector-only remote probes that cularly useful for microfluidic NMR applica-can be inserted from the top or bottom into the tions. The same probe is shown in (e) with a NMR imaging assembly, so that the well mounted holder for a microfluidic chip that is...

Miniaturized fluid handling devices have recently attracted considerable interest and gained importance in many areas of analytical chemistry and the biological sciences [50], Such microfluidic chips perform a variety of functions, ranging from analysis of biological macromolecules [51, 52] to catalysis of reactions and sensing in the gas phase [53, 54], They commonly consist of channels, valves and reaction... 

Fig. 2.6.11 Flow dispersion profiles obtained with (a) a capillary, (b) with a model microfluidic chip device containing a channel enlargement, directly connected to a capillary and (c) with the same microfluidic chip connected to a capillary via a small mixing volume. A sketch of the model microfluidic device is placed at the right side of each image, drawn to...

Fang, Q., Wang, F.-R., Wang, S.-L., Liu, S.-S., Xu, S.-K., and Fang, Z.-L., Sequential injection sample introduction microfluidic-chip based capillary electrophoresis system, Anal. Chim. Acta, 390, 27, 1999. 

The microfluidic chip system for preparing a miniaturized PMBV/PVA hydrogel consists of a two-chamber chip, an aluminum custom-made chip holder, Teflon capillaries, microtubes, and syringes equipped with a microsyringe pump (Fig. 15). The two-chamber chip was fabricated by a photolithographic wet etching technique. Whereas both channels and chambers (200 pm in depth) were fabricated on the top plate, only chambers (200 pm in depth) were fabricated on the bottom plate. 

Fig. 16 Fluorescence images of LIVE/DEAD assays of the L929 cells encapsulated for 4 days (a) in the miniaturized PMBV/PVA hydrogel formed in the microfluidic chip, and (b) in the bulk PMBV/PVA hydrogel formed in the 96-well microplate. Green fluorescence indicates live cells and red fluorescence indicates dead cells. Scale bar 100 pm...

Fig. 17 Viability of L929 cells after 4 and 8 days of encapsulation in miniaturized PMBV/PVA formed in a microfluidic chip and in bulk PMBV/PVA hydrogel formed in a 96-well microplate...

In this chapter we first discuss the fundamentals and the design aspects of an integrated optical YI sensor (Sect. 10.2), followed by a description of the experimental setup (Sect. 10.3). In the result section (Sect. 10.4) both protein and vims detection experiments are discussed. Section 10.5 demonstrates the use of microfluidic chips for efficient sample handling in combination with the YI sensor. This chapter concludes with a discussion on the prospects of the sensor for point-of-care diagnostics. 

However, current forms of LOAC devices have many components external to the microfluidic chip such as valves, pumps, power supplies, electronic circuitry, and reagent/waste storage units. While these devices are a major advance on pre-existing autonomous instruments and could be deployed on a reasonable scale, they are typically too large, consume too much power and are too expensive for high-density deployment. 

Wang, C., Oleschuk, R., Ouchen, R, Fi, J., Thibault, P., and Harrison, D. J. (2000). Integration of immobilized trypsin bead beds for protein digestion within a microfluidic chip incorporating capillary electrophoresis separations and an electrospray mass spectrometry interface. Rapid Commun. Mass Spectrom. 14, 1377—1383. 

As expected, the lower flow rates and injection volumes resulted in broader peaks when using the microfluidic system. At an injection volume of 0.1 pL, 85% of the band broadening can be contributed to the microfluidic chip, independent of the flow rate. The reason is that the connections and channels of the chip... 

The band broadening and the analyte dilution resulting from extracolumn band broadening were compared between the microfluidic chip system and the conventional macro-scale system. For a proper comparison, we calculated the analyte concentration at the peak maximum of the bioactive peaks (Cmax) from E-64 injections in both systems. It turned out that the dilution factor when comparing the concentration at peak maximum with the injected concentration was only 10% higher for the microfluidic chip system in comparison to the conventional macro-scale system. 

B. Zheng, L.S. Roach, and R.F. Ismagilov Screening of Protein Crystallization Conditions on a Microfluidic Chip Using Nanoliter-Size Droplets. J. Am. Chem. Soc. 125, 11170 (2003). 

X Continuous-Flow pI-Based Sorting of Proteins and Peptides in a Microfluidic Chip Using Diffusion Potential (from Song, Y.-A., et ah, 2006)... 

The sequence includes several synthetic steps over polymer-supported catalysts in directly coupled commercially available Omnifit glass reaction columns [41] using a Syrris Africa microreactor system [14], Thales H-Cube flow hydrogenator [32] and a microfluidic chip. The process affords the alkaloid in 90% purity after solvent evaporation, but in a moderate 40% yield. After a closer investigation it was concluded that this is due to the poor yield of 50% in the phenolic oxidation step. On condition that this is resolved with the use of a more effective supported agent, the route would provide satisfactory yields and purities of the product. 

A microfluidic chip has been developed for rapid screening of protein crystallization conditions (Hansen et al., 2002) using the free interface diffusion method. The chip is comprised of a multilayer, silicon elastomer and has 480 valves operated by pressure. The valves are formed at the intersection of two channels separated by a thin membrane. When pressure is applied to the top channel it collapses... 

Fig. 22 Images and data representing development and application of DLS on a chip a one iteration in the design of a microfluidic DLS fabricated from aluminum with the surface anodized black to reduce surface reflections b image of a microfluidic chip that integrates polymer synthesis with DLS. The machined channels have been covered by a Kapton sheet fixed with adhesive c data for temperature depended micelle formation of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic P85) at 2% by volume in water. (Derived from [106] with permission)...

Fig. 23 a Image of a microfluidic chip used for IFT measurements filled with liquid dye to illuminate channels. To perform the measurement, drops are injected (fluid la and b) are injected into an immiscible stream (2). Additional immiscible matrix is added (3a and 3b) conveying the drops into channel 4 for analysis and measurement. Constrictions in channel 4 accelerate/stretch the drops. Multiple constrictions enable measurement at different interface age. The channel geometry is shown schematically in the inset (from [108]). b Interfacial tension (ct) of water/ethylene glycol mixtures (binary drops) in PDMS oil, as a function of composition ((j)). (Reproduced with permission from [109])... 

Jia, Z-J., Q. Fang, and Z-L. Fang. Bonding of glass microfluidic chips at room temperatures. Anal. Chem. 16, 5597-5602 (2004). 

Yin, H., Killeen, K., Brennen, R., Sobek, D., Werlich, M., and van de Goor, T., Microfluidic chip for peptide analysis with an integrated HRLC column, sample enrichment column, and nanoelectrospray tip, Analytical Chemistry 11(2), 527-533, 2005. 

Chapter 11, Fig. 19. Schematic view of perfluorocarbon-implemented microfluidics for chemists. Capillary cartridges preloaded with plugs of reagents separated by gas bubbles within a perfluorocarbon carrier fluid are fitted onto a microfluidic chip where the substrate stream merges with the reagent plugs. From Ref. [102], with permission. 

FIGURE D.3 CaUper s microfluidics chip fabricated in glass. 

M. G. Roper, C. J. Easley, and J. P. Landers, Advances in Polymerase Chain Reaction on Microfluidic Chips, Anal. Chem. 2005, 77, 3887 K. D. Dorfman, M. Chabert, J.-H. Codarbox, G. Rousseau, P. de Cremoux, and J.-L. Vtovy, Contamination-Free Continuous Flow Microfluidic Polymerase Chain Reaction for Quantitative and Clinical Applications, Anal. Chem 2005,... 

Although most photoresists are generally considered to be sacrificial materials, liquid-type negative photoresists, such as SU-8, can be used to create microchannels within microfluidic chips [20]. The photoresist then becomes a structural material, in such a way that its thickness determines the depth of the microchannel. A negative dry photoresist... 

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