Fig. 17.

Chemical patterning with 2D microfluidic devices. (a) A schematic of the microfluidic network and fluorescence micrographs of a periodic overlapping sawtooth gradient of fluorescein and TMRE in ethanol. The plot below the micrograph shows the numerically calculated fluorescence intensity profile across the broad channel. (Reprinted with permission from ref. 204. Copyright (2001) by The American Chemical Society). (b) Experimental set-up for differential manipulation of regions of a single bovine capillary endothelial cell using multiple laminar flows. Lower panel shows a close-up of the point at which the inlet channels combine into one main channel. (Reprinted with permission from ref. 205. Copyright (200) by The Nature Publishing Group). (c) Fluorescence images of a single cell after treatment of its right pole with Mitotracker Green FM and its left pole with Mitotracker Red CM-H2XRos. The entire cell is treated with the DNA-binding dye Hoechst 33342. (Reprinted with permission from ref. 205. Copyright (2001) by The Nature Publishing Group). (d, e) Overlapping diffusive gradients. Color dyes were introduced through different access ports and their concentration was maintained with a constant flow rate. For each dye an independent gradient formed with 120° angular displacement. Overlapping the three gradients results into a blend of dye concentrations where each spatial location has different combinations of dye concentrations. Scale bar 500 μm. (Reprinted from ref. 209 with permission from The Royal Society of Chemistry). (f) A microfluidic chemotaxis device design: details of a three channel unit. Motile cells are injected into the center channel. Dual chemical gradients (schematically illustrated with gradient-colored triangles) are generated in the center channel by pumping media containing different concentrations of chemoattractants through the two side channels. (Relevant reference: 210).