Microfluidic channel network

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. 

Inside microfluidic channels the flow is laminar. Due to the absence of turbulences different media do not mix or mix only spontaneously and very slowly. Automatic elements can only operate correct in the presence of sufficient process medium. Otherwise, in the absence of stimulation, the control functionality can not be performed. Therefore, inside microfluidic channel networks the realisation of a recirculation is recommended which can provide an independency from the state (open or closed) of the active hydrogel components. 

J.-L. (2005) Using microfluidic channel networks to generate gradients for studying cell migration. In Guan J.-L. (ed.). Cell Migration Developmental Methods and Protocols. Humana, Totowa, NJ, pp. 347-356... 

Whitesides and coworkers combined microfluidic networks with a PDMS platform to create patterned gradients of biomolecules on a surface.121 This method involves a two-step process (1) formation of a gradient of avidin within well-defined patterns by use of microfluidic channels and (2) specific interaction between the avidin gradient pattern and biotin. Such patterns with a density gradient of immobilized biomolecules may find application in studies on cell development and function. 

The basic unit operation on the pressure driven laminar flow platform is the contacting of at least two liquid streams at a microfluidic channel junction (see Fig. 7). This leads to controlled difflisional mixing at the phase interface, e g. for initiation of a (bio-) chemical reaction [105]. It can also be applied for the lateral focusing of micro-objects like particles or cells in the channel [95]. The required flow focusing channel network consists of one central and two S5munetric side channels, connected at a junction to form a common outlet channel. By varying the ratio of the flow rates, the lateral width of the central streamline within the common outlet channel can be adjusted very accurately. Consequently, micro-objects suspended in the liquid flowing... 

Unfortunately, even though control of relative flow resistances within channel networks is straightforward, it appears to be somewhat overlooked by much of the microfluidic research community. Through more judicious design constraints, researchers could benefit greatly from this simple method. Harrison and coworkers utilized relative flow resistances to reproducibly sample small... 

Fig. 6 Examples of vessel-on-a-chip platform. (A) Schematic of two PDMS chamber connected by a membrane and (B) the image of fabricated device (Adapted from [63]). (C) Long microfluidic channel with a consecutive flow and (D) repeatedly stretched and relaxed elastic membrane (Adapted from [64]). (E) Three-dimensional perfusable tubular capillary network in a microfluidic platform (Adapted from [65]). (F) Microvasculare network on a chip filled with fibrin gel inside the main channel (Adapted from [66]).

Conceptual drawing of microflow stmctures within a microfluidic network for the particle crossover within microfluidic channels. It is possible to achieve the particle crossover from one to another fluid streams without losing particles into multiple parallel channels, (b) Schematic sketch of a representative example of continuous biosensing using the particle crossover mechanism. The concentration of biotinylated FITC molecules can be determined by measuring the fluorescence intensity of the biotinylated FITC bound streptavidin-coated 8-pm-diameter particle at the detection window using an epifluorescence microscope [5]... 

Most centrifugal microfluidic systems are networks of vessels and interconnecting channels performing assays, chemical synthesis, or preparative protocols at the downstream end. To provide quantitative results, a metering of the volumes is required. However, an accurate and precise metering is not only essential for the chemistry, but it is also of key relevance for the centrifugal flow control via the radial coordinates r <, r > and r of the volume within the channel network (see for instance Eqs. 7, 9,11, and 13). 

Fluid manipulation and transport of samples and reagents are often implemented in a network of microfluidic channels that intercoimect the various components on a common substrate. These microchannels have dimensions ranging from tens of run to hundreds of pm - comparable to, or in many cases much smaller than, a human... 

Immunoassay Microfluidic networks have high resolution and contrast capabilities for simultaneously patterning lines of proteins onto a surface. This has been utilized, for example, by Bernard et al. [13], to create a miniaturized mosaic of inununoassays by patterning lines of antigens on PDMS surfaces by a microfluidic network and delivering the analytes by another set of microfluidic channels at right angles to the direction of the first set. Microfluidic separations have also been combined with... 

Research in laser micromachining wiU continue to new methods for the fabrication of microfluidic devices, particularly from polymers and glass. The development of 3D channel networks is important for numerous fluidic applications which wiU fuel the future demand for more research in this area. As these methods are refined, the processes wiU be tailored to processing of many different types of polymers. Future work will continue to seek methods to decrease the roughness of microchannels. 

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