Microfluidic Flow

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].

A novel 24-channel HPLC by Nanostream called Veloce was introduced at PITTCON 04. The column cassette contains 24 parallel microbore columns. The eluted samples are detected by a 24-channel UV filter photometer. The advantage of such a system is that it allows one to work with multiple samples simultaneously. Other interesting systems for parallel HPLC were those introduced by Eksigent, based on microfluidic flow control, and Sepiatec GmbH, which allows the processing of 75 multiple-well plates. 

For a microfluid flowing through N tanks in series Eq. 6.8 gives... 

Wang, H.-Y., Bhunia, A. K., and Lu, C. (2006). A microfluidic flow-through device for high throughput electrical lysis of bacterial cells based on continuous DC voltage. Biosens. Bioelectron. 22,582-588. 

J.S. Rossier, P. Morier and F. Reymond, Patent Microfluidic Flow Monitoring Device, 2003, WO 2003/004160 A004161. 

The liquid pumping in the microfluidic chip is mostly achieved by using electro-osmotic flow (EOF) [324]. Other liquid pumping methods have also been employed for microfluidic flow. Flow has been employed for fraction collection and generation of concentration gradient. Laminar flow in the microfluidic channel allows liquid-liquid extraction and microfabrication to occur within the channels. Moreover, valving and mixing are needed in order to achieve a better flow control. All these microfluidic flow operations are further described in subsequent sections. 

Various Mathematical Modeling and Stimulation Methods to Study Microfluidic Flow... 

The book is divided into several chapters which include micromachining methods, microfluidic operations (microfluidic flow, sample introduction, sample preconcentration), chemical separations, detection technology, and various chemical and biochemical analysis (applications on cellular analysis, nucleic acid analysis, and protein analysis). Emphasis will be placed on analytical applications although the basic principles about micromachining and fluid flow and control will also be covered only to the extent that their understanding will assist the exploitation of the microfluidic technology on analytical applications. 

Garstecki, P., Gitlin, I., DiLuzio, W., Whitesides, G.M., Kumacheva, E. and Stone, H.A. (2004). Formation of monodisperse bubbles in a microfluidic flow-focusing device. Appl Phys. Lett. 85,2649-2651. 

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