FIG. 3.

Stop flow lithography (SFL) in UV-cured PDMS microfluidic chips. (a) Schematic illustration depicting the synthesis of 3 color-coded microparticles by cyclically (1) exposing UV through a photomask to a laminar co-flow of blue, red, and green PEGDA solutions in a microchannel and (2) applying inlet pressure to purge photocrosslinked microparticles. (b) and (c) Schematic top-down views of the microchannel shown in (a). Orange (left panel in (b)) and co-flow of blue, red, and green (left panel in (c)) PEGDA solutions were exposed to UV through photomasks (black circles and round-rimmed rectangles). Optical micrographs showing synthesized cylindrical (middle panel in (b)) and bar (middle panel in (c)) microparticles. Scale bars in (b) and (c) are 100 and 50 μm, respectively. Fluorescence micrographs displaying the microparticles shown in the middle panels, conjugated with rhodamine-acrylate (orange; right panel in (b)) or blue-, red-, and green-quantum dots (QDs; right panel in (c)).