Microfluidic channel

ON-LINE MONITORING OF HYDRODYNAMIC FLOW PROFILES IN MICROFLUIDIC CHANNELS BASED UPON MICROELECTROCHEMISTRY... 

Miniaturisation of various devices and systems has become a popular trend in many areas of modern nanotechnology such as microelectronics, optics, etc. In particular, this is very important in creating chemical or electrochemical sensors where the amount of sample required for the analysis is a critical parameter and must be minimized. In this work we will focus on a micrometric channel flow system. We will call such miniaturised flow cells microfluidic systems , i.e. cells with one or more dimensions being of the order of a few microns. Such microfluidic channels have kinetic and analytical properties which can be finely tuned as a function of the hydrodynamic flow. However, presently, there is no simple and direct method to monitor the corresponding flows in. situ. 

OPTIMISATION OF MICROBAND ELECTRODE SIZES AND LOCATIONS WITHIN A RECTANGULAR MICROFLUIDIC CHANNEL FOR ELECTROCHEMICAL MONITORING OF HYDRODYNAMIC FLOW PROFILES... 

Abott et al. demonstrated that the flow in a microfluidic channel can be controlled by using the wetting gradient generated by electrochemical reactions ofthe surfactant... 

There are more important and useful relations that can be used in design and analysis of flow in microfluidic channel network with changing sections. Since... 

A knowledge of v can give an indication of the transit time of a plug of chemical or an ensemble of cells through a microfluidic channel network and thus to assess whether there is enough time for complete mixing or chemical reaction. Both Eq. (11) and Eq. (12) are strictly only valid under idealized conditions (i.e. incompressible and non-viscous fluids and steady flow), but can still be helpful for overall estimation and assessment. 

K. Macounova, C.R. Cabrera, and P. Yager, Concentration and separation of proteins in microfluidic channels on the basis of transverse IEF. Anal. Chem. 73, 1627—1633 (2001). 

E. Eteshola and D. Leckband, Development and characterization of an ELISA assay in PDMS microfluidic channels. Sens. Actuators B. 72, 129—133 (2001). 

In this method, NWs can be aligned by passing a suspension of NWs through microfluidic channel structures, for example, formed between a poly(dimethylsiloxane) (PDMS) mold 49 and a flat substrate (Fig. 11.3a). Images of NWs assembled on substrate surfaces (Fig. 11.3b) within micro-fluidic flows demonstrate that virtually all NWs are aligned along the flow direction. This alignment readily extends over hundreds of micrometers, and... 

In addition to absolute pressure measurements, pressure sensors can be used to determine flow rates when combined with a well-defined pressure drop over a microfluidic channel. Integration of optical waveguide structures provides opportunities for monitoring of segmented gas-liquid or liquid-liquid flows in multichannel microreactors for multiphase reactions, including channels inside the device not accessible by conventional microscopy imaging (Fig. 2c) (de Mas et al. 2005). Temperature sensors are readily incorporated in the form of thin film resistors or simply by attaching thin thermocouples (Losey et al. 2001). 

While the ring length can be increased simply by increasing the ring radius, this again leads to large structures that have a poor cross-section with the microfluidic channels. As in the case of the MZI-based devices, incorporating a folded... 

Fig. 13.9 (a) The MNF sensor with microfluidic channel, (b) Measured optical transmission versus refractive index of the liquid in the channel for two sensors with different MNF diameter at the waist curve 1 1.6 pm curve 2 700 nm. Circles are measurement data points. The arrow... 

Polynkin, P. Polynkin, A. Peyghambarian, N. Mansuripur, M., Evanescent field based optical fiber sensing device for measuring the refractive index of liquids in microfluidic channels, Opt. Lett. 2005, 30, 1273 1275... 

Atsuta, K. Suzuki, H. Takeuchi, S., A parylene lift off process with microfluidic channels for selective protein patterning, J. Micromech. Microeng. 2007, 17, 496 500... 

B. Zheng, J.D. Tice, and R.F. Ismagilov Formation of Droplets of Alternating Composition in Microfluidic Channels and Applications to Indexing of Concentrations in Droplets-Based Assays. Anal. Chem. 76, 4977 (2004). 

SIP-driven polymer brush library fabrication leverages the fact that the polymerization initiation species are permanently bound to the substrate. Since the initiators are tethered, controlled delivery of monomer solution to different areas of the substrate results in a grafted polymer library. In NIST work, initiators bound via chlorosilane SAMs to silicon substrates were suitable for conducting controlled atom transfer radical polymerization (ATRP) [53] and traditional UV free radical polymerization [54, 55]. Suitable monomers are delivered in solution to the surface via microfluidic channels, which enables control over both the monomer solution composition and the time in which the solution is in contact with the initiating groups. After the polymerization is complete, the microchannel is removed from the substrate (or vice versa). This fabrication scheme, termed microchannel confined SIP ([t-SIP), is shown in Fig. 10. In these illustrations, and in the examples discussed below, the microchannels above the substrate are approximately 1 cm wide, 5 cm long, and 300-500 [tm high. 

Recently Allbritton and Li coated polydimethylsiloxane (PDMS) microfluidic channels with BP [36]. Upon irradiation in the presence of a monomer solution, they were able to graft poly(acrylic acid) and poly(ethylene glycol) monomethoxyl acrylate to the interior walls of the channels. This is a significant achievement since the device did not require disassembly in order to modify the channel walls. The electrophoretic separation of the modified channels was different from the native channels. This technique holds particular promise for the microfluidic separations commimity. 

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