FIG. 4.

Characterizations of microparticle dimensions and oxygen inhibition layers. (a) Schematic illustrations depicting an experimental set-up immediately after UV exposure to measure the diameter (d_{microparticle}) of photocrosslinked PEGDA microparticles (top) and 5–10 s after UV exposure to measure the height (h_{microparticle}) of the microparticles (bottom). Light and dark red represent a PEGDA pre-polymer solution and photocrosslinked microparticles, respectively. The dotted red rectangle in the bottom panel is the original position of the microparticle shown in the top panel. (b) Optical micrographs showing photocrosslinked microparticles in thermally (Sylgard 184; left) and UV (X-34-4184; right)-cured PDMS chips. The scale bar is 50 μm. (c) Bar graphs displaying d_{microparticle} and h_{microparticle} of the microparticles shown in (b). (d) Bar graph displaying the sum of two oxygen inhibition layers (2${\delta }_{O_2\hspace{0.17em}inhibition}$) in contact with top and bottom of PDMS. ns and **** denote the statistical insignificance with p > 0.5 and significance with p < 0.0001, respectively.