Microfluidic devices

Polymers have come a long way from parkesine, celluloid and bakelite they have become functional as well as structural materials. Indeed, they have become both at the same time one novel use for polymers depends upon precision micro-embossing of polymers, with precise pressure and temperature control, for replicating electronic chips containing microchannels for capillary electrophoresis and for microfluidics devices or micro-optical components. 

While the previous studies refer to straight channels exceptionally, microfluidic devices often comprise channels with a curvature. It is therefore helpful to know how hydrodynamic dispersion is modified in a curved channel geometry. This aspect was investigated by Daskopoulos and Lenhoff [155] for ducts of circular cross-... 

Mitchell, M. C., Spikmans, V., Bessoth, F., Manz, a., de Mello, A., Towards organic synthesis in microfluidic devices multicomponent reactions for the construction of compound libraries, in van den Berg, A., Olthuis, W., Bergveld,... 

D., Hocker, H., Legewie, F., Poprawe, R., Wehner, M., Wild, M., Laser processing for manufacturing microfluidic devices, in Eheeeld, W. (Ed.), Microreaction Technology 3rd International Conference on Microreaction Technology, Proc. of IMRET 3, pp. 80-89, Springer-Verlag, Berlin (2000). 

In addition to the spreading dynamics, the stacking structure of the self-spreading lipid bilayer is also controllable via the NaCl concentration [54, 55]. Further experimental and theoretical investigations regarding the control of self-spreading are required before we will be able to easily control the self-spreading behavior in microfluidic devices. 

The most intriguing aspect of the self-spreading lipid bilayer is that any molecule in the bilayer can be transported without any external bias. The unique characteristic of the spreading layer offers the chance to manipulate molecules without applying any external biases. This concept leads to a completely non-biased molecular manipulation system in a microfluidic device. For this purpose, the use of nano-space, which occasionally offers the possibility of controlling molecular diffusion dynamics, would be a promising approach. 

The presented results show that the simple asymmetric pattern caused directional deformations and transport of a droplet. This technique is applicable to generation of a flow in microfluidic devices. 

Fig. 2.6.10 Specialized experimental set-up for microfluidic flow dispersion measurements. Fluid is supplied from the top, flows via a capillary through the microfluidic device to be profiled and exits at the bottom. The whole apparatus is inserted into the bore of a superconducting magnet. Spatial information is encoded by MRI techniques, using rf and imaging gradient coils that surround the microfluidic device. They are symbolized by the hollow cylinder in the figure. After the fluid has exited the device, it is led through a capillary to a microcoil, which is used to read the encoded information in a time-resolved manner. The flow rate is controlled by a laboratory-built flow controller at the outlet [59, 60].

The gas flow direction was from the top to bottom of the figure. No divergence is observed in the dispersion curve of the capillary, indicating that under the given conditions the dispersion of flow is small, and that this scheme is thus adequate to study the dispersion within a device of interest. This may appear unexpected, as microfluidic devices are usually assumed to exhibit laminar flow, however it can be explained by the fast lateral diffusion of individual gas molecules, which uniformly sample the whole cross section of the tube in a very short time compared with the travel time. Below each image, its projection is shown together with an independ-... 

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...

Ramsey, J.D., Jacobson, S.C., Culbertson, C.T., Ramsey, J.M. (2003). High efficiency, two-dimensional separations of protein digests on microfluidic devices. Anal. Chem. 75, 3758-3764. 

Pittman, J.L., Terekhov, A.I., Suljak, S.W., Gilman, S.D. (2003). Optically gated vacancy electrophoresis in microfluidic devices. Anal. Chim. Acta 496, 195-204. 

Benninger, R. K. P., Hofmann, O., McGinty, J., Requejo-Isidro, J., Munro, I., Neil, M. A. A. and French, P. M. W. (2005a). Time-resolved fluorescence imaging of solvent interactions in microfluidic devices. Opt. Express 13, 6275-85. 

Erickson D., Li D., Integrated microfluidic devices, Anal. Chim. Acta 2004 507 11 -26. 

Andersson H, van den Berg A (2003) Microfluidic devices for cellomics a review. Sensor Actuat B-Chem 92 315-325... 

J. Khandurina, T.E. McKnight, S.C. Jacobson, L.C. Waters, R.S. Foote, and J.M. Ramsey, Integrated system for rapid PCR-based DNA analysis in microfluidic devices. Anal. Chem. 72, 2995-3000 (2000). 

J. Kruger, K. Singh, A. O Neill, C. Jackson, A. Morrison, and P. O Brien, Development of a microfluidic device for fluorescence activated cell sorting. J. Micromech. Microeng. 12, 486-494 (2002). 

There are more issues and complexity to be considered if various micro-electromechanical (MEMS)-type devices are included in the macroelectronics tool kit. As described previously, the materials and devices required for TFTs and circuits can provide adequate electromagnetic (visible and RF) sensitivity for many image-type applications. These materials may also provide satisfactory performance in pressure and strain sensors. Nanotube/nanowire-based devices look promising for various chem-bio sensors.85 However, there is little that is known about the ability to integrate printed microfluidic devices (and other such devices with moving parts) into a roll-to-roll-type process. 

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