Lab-on-a-chip systems

Manipulation of a droplet on a solid surface is of growing interest because it is a key technology to construct lab-on-a-chip systems. The imbalance of surface tensions is known to cause spontaneous motion of a droplet on the surface, as mentioned above. The wetting gradient causing liquid motion has been prepared by chemical [32], thermal [37], electrochemical [3] and photochemical [38-40] methods. 

Topics covered will include the characterisation, performance and properties of materials and technologies associated with miniaturised lab on a chip systems. The books will also focus on potential applications and future developments of the materials and devices discussed. 

FIGURE 10.6 Schematic drawings of a lab-on-a-chip system. (Top) Multisensor chip consists of pH, p02, and conductivity (impedance) electrodes incorporated in a microfluidic cell. (Bottom) The layout of electrodes on the chip. (Reproduced from [91], with permission from Elsevier.)... 

O. Geschke, H. Klank, and P. Telleman, Microsystem Engineering of Lab-on-a-chip System, Wiley-VCH (2004). 

Figure 5. Photograph of an autonomous lab-on-a-chip system (top) configured for remote field monitoring of phosphorus in natural waters. Bottom is a closeup of the detector area of the system.

S. Ferko, V. A. VanderNoot, J. A. A. West, R. Crocker, B. Wiedenman, D. Yee, and J. A. Fruetel, Hand-Held Microanalytical Instrument for Chip-Based Electrophoretic Separations of Proteins, Anal. Chem. 2005, 77, 435 J. G. E. Gardeniers and A. van den Berg, Lab-on-a-Chip Systems for Biomedical and Environmental Monitoring, Anal. Bioanal. Chem 2004,378, 1700 J. C. McDonald and G. M. Whitesides, Poly(dimethylsiloxane) as a Material for Fabricating Microfluidic Devices, Acc. Chem. Res. 2002,35, 491 Y. Huang,... 

An innovative electrochemical lab on a chip system has been developed by Popovtzer et al. (2006) for the measurement of microbial responses to toxic chemicals. The miniaturized device was designed in two parts to enable multiple measurements a disposable silicon chip containing an array of nano-volume electrochemical cells that house the biological material, and a reusable unit that includes a multiplexer and a potentiostat connected to a pocket PC for sensing and data analysis. 

The wavelength detectors can also be integrated into lab-on-a-chip systems due to their compactness. Applications that are anticipated to benefit from the spectrometers include spectroscopy-on-a-chip applications for reagentless identification of analytes (e.g., biomolecules or chemicals) in fluidic and aerosol samples. 

In addition to the aforementioned capabilities, this lab on a chip system could be easily adapted to different apphcations, including specific identification of chemicals by using binding techniques, i.e., each electrochemical cell in the array can incorporate different biosensors. Thus, large amount of analytes can be detected simnltaneonsly and independently. Similarly, in experiments aiming to analyze physiological reactions, bacteria harboring different types of promoters can be introduced to the chambers, and thus, this lab on a chip can detect a variety of toxicant types simultaneously. 

J. Hoffmann, D. Mark, R. Zengerle, and F. von Stetten, Liquid Reagent Storage and Release for Centrifugally Operated Lab-on-a-Chip Systems Based on a Bnrstable Seal, 15 ed 2009. 

Lab-on-a-chip systems have been previously demonstrated to have significant utility in the field of analytical chemistry.1 Lab-on-a-chip systems miniaturize standard bench-scale operations that are normally carried out in containers of the order of millilitres or litres to chip-scale operations in channels and droplets on the order of nanolitres to microlitres. The majority of lab-on-a-chip devices proposed thus far utilize micrometer-scale sealed channels. These sealed channels can then be used to separate, combine and mix chemical reagents in such a way as to recreate traditional wet chemistry protocols on a much smaller scale. When used in such a manner, these sealed channels are referred to as continuous flow microfluidic channels.2 4... 

Lab on a Chip System Using a TSIL as a Soiubie Support... 

A powerful tool to synthesize easily minute amounts of organic compounds on demand by using both ionic liquids droplets as microreactors and electrowetting as a fluidic motor has been described. These droplets can be moved, divided and combined on an open digital microfluidic lab-on-a-chip system [60]. This has been demonstrated with BTS ILs used as reaction media and supports, properly functionalized to perform the Grieco s multicomponent synthesis of tetrahydroquinolines (Fig. 5.5-3). It is assumed that this original concept should impact many areas, notably combinatorial chemistry, parallel synthesis, optimization of protocols, synthesis of dangerous products and embedded chemistry in a portable device. 

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