FIG. 5.

Stronger interfacial bonding and enhanced productivity in UV-cured PDMS chips. (a) Schematic illustration depicting an experimental set-up designed to measure the interfacial burst pressure: moderate (left) and excessive (right) inlet pressures into PDMS microfluidic chips. The red droplet represents the interfacial leakage due to burst. (b) Bar graph displaying the measured burst pressure of thermally cured PDMS (Sylgard 184) chips at 70 °C (left) and room temperature (middle) and that of UV-cured PDMS (X-34-4184) chips (right). ** and **** denote the statistical significance with p < 0.01 and p < 0.0001, respectively. (c) and (d) Stop flow lithography (SFL) in thermally (Sylgard 184 (c)) and UV (X-34-4184 (d))-cured PDMS chips with a flow time of 40 ms and inlet pressures of 20 (c) and 400 (d) kPa, respectively. Optical micrographs in left panels show PEGDA microparticles immediately after UV exposure (top) and those after 1 cycle of SFL (i.e., stop-UV exposure-hold-flow; bottom). Yellow dotted arcs represent the field of view of a 20× objective lens (1.25 mm in diameter) through which photomasked UV is propagated. Optical micrograph in the right panel shows an undesired block of PEGDA (c) and intact microparticles (d) photocrosslinked along the microchannel after 25 cycles of SFL, respectively. Scale bars in the left and right panels are 200 and 50 μm.