Schematic of the working principle of the present continuous-flowing micro reactor. Top: Temperature distribution profile along the microchannel; Middle: Pressure distribution profile along the microchannel; Bottom: Basic design of the present chip.
Hydrodynamic phase chart of the chip design (physical properties were taken at 50 °C). Inset figure shows the effects of the channel depth on the high-temperature reaction time and the operable flow rate.
Layout of the present chip (a) and its fabrication process (b). Inserted figures in (a) showed the detail of the key components of the chip. Inserted SEM photos (from top to bottom) showed the cross section of the final isolation trench, the inlet with 5 μm/20 μm filters, and the pressure regulating microchannel and the outlet. All the scale bars were 300 μm.
Photos of the experimental system and the fabricated chip. (a) Photo of the experimental set-up with a packaged chip as inset figure. (b) Photo of the chips with glass (left) and silicon (right) sides upwards.
Infrared photos of the chips without (a) and with (b) thermal isolation trenches before package. The photos were taken by an infrared thermograph (FLIR SC7300) from the glass side of the chip.
Experimental and numerical pressure variation in the reaction zone with the flow rates at different TP . The dashed circles indicated that the circumscribed line and marker stand for the same group, with lines for the numerical simulation results and markers for the experimental measurements. For the case with TP of 50 °C, only numerical results were included. DI water was used as the working fluid. Error bar stands for three independent trials.
Variation of the absorbance with the total phosphorus concentration at 700 nm. Inset figure showed the comparison of the chip (with different flow rates, i.e., different digestion times) and off-chip thermal digestion performances.
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