Fig. 18.

Chemical patterning with 3D microfluidic devices. (a) Branched microvascular network embedded in PLA substrates which incorporates a hierarchy of microchannel diameters. An aqueous solution of blue food dye was injected into the interconnected microchannel array for visualization purposes. (Reprinted with permission from ref. 219. Copyright (2009) by John Wiley and Sons). (b) A microfluidic network having the geometry of a basketweave. The channels were filled with an aqueous solution of fluorescein (green) or Cascade Blue (blue) and illuminated with UV light. (Reprinted with permission from ref. 221. Copyright (2003) by The American Chemical Society). (c, d) Cross-sectional views of cell-seeded microfluidic scaffolds. Dispersed cells are shown as double circles. Microchannels are shown as squares. The pink shading represents steady-state 3D distributions of solutes: in (c), reactive solute is delivered via the channels and is consumed by cells as it diffuses into the matrix; in (d), non-reactive solute is delivered via the two channels on the left and extracted by the channels on the right. (Reprinted with permission from ref. 229. Copyright (2007) by The Nature Publishing Group). (e) The gradient-generating region of a microfluidic device features a tapered microchamber to produce a nonlinear gradient. By changing the shape of the gradient-generating region it is possible to change the shape of the chemical gradient. (Reprinted with permission from ref. 231. Copyright (2007) by The American Chemical Society). (f) A self-assembling microfluidic device with PDMS inlets/outlets attached to a Si substrate and with PDMS channels integrated with a differentially crosslinked SU-8 film. Fluorescence images showing the flow of fluorescein (green)/rhodamine B (red) through a dual channel device. (Reprinted with permision from ref. 232. Copyright (2011) by The Nature Publishing Group).