Microfluidic networks

S.K.W. Dertinger, D.T. Chiu, N.L. Jeon, and G.M. Whitesides, Generation of gradients having complex shapes using microfluidic networks. Anal. Chem. 73, 1240-1246 (2001). 

One crucial and hence central step in the design, fabrication and operation of DNA chips, DNA microarrays, genosensors and further DNA-based systems described here (e.g. nanometer-sized DNA crafted beads in microfluidic networks) is the immobilization of DNA on different soHd supports. Therefore, the main focus of these two volumes is on the immobilization chemistry, considering the various aspects of the immobihzation process itself, since different types of nucleic acids, support materials, surface activation chemistries and patterning tools are of key concern. 

Delamarche, A. Bernard, H. Schmid, B. Michel, and H. Biebuych, Patterned delivery of immunoglobulins to surfaces using microfluidic networks, Science 276, 779—781 (1997). 

Figure 1.70 (a) Schematic of a 3-inlet/9-outlet microfluidic network, (b) Linear and (c, d) parabolic gradients of fluorescein in solution. The inlet concentrations are indicated by I,. The plots show the fluorescence intensity profile across the broad outlet channel. The theoretically calculated concentration profiles and the contributions of the individual inlets are marked [117] (by courtesy of ACS). 

Figure 1.71 (a) Schematic of a 2-inlet/8-outlet microfluidic network in parallel. 

M 34] [P 32] Linear and parabolic gradients can be generated at the outlet of the microfluidic network. In all cases, calculated concentrations [see Figure 1.70 ( )] are in a good agreement with the experimentally observed concentration profiles. 

Figure 1.191 (a) Construction of the microfluidic chip and (b) schematic of the microfluidic network for feeding analyte and buffer solutions [164] (by courtesy of RSC). 

Figure 1.192 (a) Fluorescence micrograph in the main channel of the microfluidic network, (b) Discontinuous, step-like concentration profiles generated in this way [164] (by courtesy of RSQ. 

MHD) directed flow in microfluidic networks. Micro Total Analysis Systems, Proceedings 5th a7i45 Symposium, Monterey, CA, Oct. 21-25, 2001, 577-578. 

Li, Y., Buch, J.S., Rosenberger, F., DeVoe, D.L., Lee, C.S., Integration of isoelectric focusing with parallel sodium dodecyl sulfate gel electrophoresis for multidimensional protein separations in a plastic microfluidic network. Anal. Chem. 2004, 76, 742-748. 

Sniadecki, N.J., Chang, R., Beamesderfer, M., Lee, C.S., DeVoe, D.L., Field effect flow control in a polymer T-Intersection microfluidic network. Micro Total Analysis Systems 2003, Proceedings 7th liTAS Symposium, Squaw Valley, CA, Oct. 5-9, 2003, 899-902. 

Similarly, substrates can be patterned with biomolecules by means of a microfluidic network (pFN).119 Bernard et al.87 presented patterns of antigen made by flow of solution in a microfluidic network. After a blocking step with BSA, the solution with... 

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. 

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