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Optofluidic planar reactors for photocatalytic water treatment using solar energy
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) Schematic and (b) cross-sectional view of the photocatalytic microfluidic reactor. The device is constructed by two -coated glasses separated by a thin layer of microstructured UV-cured NOA81. Tree-branch shaped microchannels are used to ensure that the solution uniformly fills the whole reaction chamber and have maximum contact with the films. The length and width of the reaction chamber are and , respectively. The films have the same surface area as the reaction chamber. The heights of the microchannels and the reaction chamber are and , respectively.

Image of FIG. 2.
FIG. 2.

Scanning electron micrographs showing the porous structure of the fabricated film. (a) Top view of the film: the submicron porous structures are beneficial as they increase the contact area between the reagents and and thus improve the photocatalytic efficiency. The inset shows the good homogeneity of the film. (b) Cross-sectional view of the film: the film is about thick and shows a good homogeneity in the depth direction.

Image of FIG. 3.
FIG. 3.

Process flow of the device fabrication and integration. Microstructured PDMS slab is replicated from the SU-8 mold in advance. (a) The microstructured slab is attached to a planar PDMS slab. (b) Liquid NOA81 is applied to fill the space between the two PDMS slabs by capillary force. (c) The NOA81 is partially cured by the UV light. (d) The microstructured PDMS slab is peeled off and the NOA81 layer is bonded to a -coated glass slide. (e) The other glass slide is bonded by UV exposure. (f) Two syringe needles are connected to the inlet and outlet using adhesive.

Image of FIG. 4.
FIG. 4.

Photograph of the fabricated planar microfluidic photocatalytic reactor.

Image of FIG. 5.
FIG. 5.

(a) Comparison of the photocatalytic reaction efficiencies. The microreactor shows much higher reaction efficiency than the container. For further comparison, the microreactor without is also tested and its reaction is found negligible. (b) The reaction rate constant of the microreactor is more than 100 times higher than that of the bulk container and presents to increase with the flow rate of the solution.

Image of FIG. 6.
FIG. 6.

(a) Transmission spectra (in the UV region) of the porous films with different thicknesses under the irradiation of solar simulator. The inset shows the relationship between the thickness of the obtained porous film and the concentration of the aqueous solution using the sol-gel method. (b) Degradation percentage as a function of the film thicknesses using the bulk container. (c) Degradation percentage as a function of the film thicknesses on the top glass using the microreactor. The film thickness on the bottom glass is kept at .

Image of FIG. 7.
FIG. 7.

Degradation percentage and reaction rate with respect to different effective residence times of the methylene blue solution in the reaction chamber. The degradation percentage increases with the effective residence time, whereas the reaction rate decreases. The inset shows that the reaction rate constant increases with the flow rate.


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Scitation: Optofluidic planar reactors for photocatalytic water treatment using solar energy