Figure 2.

Spatial positioning of biological specimens in microfluidic systems. a) A densely packed single-cell trapping array fabricated in PDMS. A microphotograph shows an overview of the device with multiple cell trap modules, which can be chemically stimulated at different concentrations. Inset shows individual fluorescently labeled cells trapped within a portion of one cell trap module²⁰. Reprinted with permission. Copyright 2011 American Chemical Society. b) A droplet-based platform for single cell screening. The platform integrates five modules for performing common droplet functions including droplet generation (A), droplet merging (B), mixing (C), incubation and storage (D) and detection (E) ²⁸. Reprinted with permission from the National Academy of Sciences. (c) Microfluidic device for rapid immobilization, imaging and sorting of C. elegans ³⁸. Movement of worms in the flow layer of the PDMS device (red) are controlled by the state of the pressure activated valves in the control layer (green). Flow of chilled liquid through the cooling channel in the control layer (blue) facilitates rapid immobilization of the worm in the imaging region. Reprinted with permission from Nature Publishing Group. d) A PDMS-based device for the trapping and orientation of individual Drosophila melanogaster embryos by passive hydrodynamics. The positioning of the embryos in a typically physically unstable and difficult to achieve orientation (long anterior-posterior axis perpendicular to coverslip) single-plane imaging of patterning events along the dorsoventral axis³⁶. Reprinted with permission from Nature Publishing Group.