Microfluidic Photocatalytic Device Utilizing Anodized Titania Nanotube Arrays: Application and Simulation Validation

Microfluidic photocatalytic reactors have advantages over conventional bulk reactors such as large surface-area-to-volume ratio and high control of fluid flow. Although titania nanotubular arrays (TNA) have shown enhanced photocatalytic degradation compared to nanoparticle films in a batch reactor configuration, their application in a microfluidic format has yet to be fully explored. The photocatalytic performance of a microfluidic reactor with TNA catalyst was compared with the performance of microfluidic format with TiO2 nanoparticulate (commercial P25) catalyst. The microfluidic device was fabricated using non-cleanroom based soft lithography, making it suitable for economical large-scale manufacturing. The photocatalytic performance was evaluated at different flow rates ranging from 25 to 200 μL/min. The TNA microfluidic system demonstrated enhanced photocatalytic performance over microfluidic TiO2 nanoparticulate layers, especially at higher flow rates (50-200 μL/min).

A computational model of the microfluidic format was developed to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. The improved performance of the TNA photocatalyst over the nanoparticle film can be attributed to higher generation of, and improved diffusion of oxidizing species. The model and microfluidic platform developed can easily be modified to suit other channel geometries and pollutants. A comparison of similar microfluidic photocatalytic platforms was made on the basis of dimensionless Peclet number. The system described in this study demonstrates high advective flow compared to otherwise similar microfluidic photocatalytic systems.