A simple design and low cost miniaturized reactor integrated with interchangeable thin film TiO 2 nanolayer was successfully fabricated for the photocatalytic degradation of azo dyes. The TiO 2 nanofilms were prepared by sol-gel dip-coating method, while the miniaturized reactor was fabricated on poly methyl methacrylate (PMMA) substrates, using a laser cutting machine. The performance of the miniaturized reactor for the photocatalytic degradation process was investigated for the degradation of a commercial dye (Novacron Red C-2BL). About 98% degradation of the commercial dye was achieved after 100 min in a stopped flow system, and 15% in a continuous flow system. The effect of different operating variables such as pH, initial flow rate, light intensity, layers of the nanoparticles, and temperature on the photocatalytic degradation was studied and the optimum operating conditions were determined to be: inlet flow rate of 0.05 ml/s, pH of 7, UV power 82 W and using a multilayer of TiO 2 thin film in the miniaturized reactor. The reaction kinetics was described as pseudo first order kinetics and rationalized using the Langmuir-Hinshelwood model.

Novel microfluidic resistive network designs have been evaluated theoretically and experimentally. Such networks are an important component of microreactor technology and are used in analytical and biomedical applications for precisely controlled and evenly stepped dilution. A detailed model and a simplification algorithm have been devised for these networks. Their combination produces novel simplified network designs that exhibit less hierarchical branching over existing network designs. Rapid prediction and optimization of a layout that meets an arbitrary outlet profile is also possible. High levels of linearity were achieved on three microdevice fluidic networks. Good agreement of the experimental results from tested devices with the model was obtained. In addition, CFD simulation of one of the designs gave good agreement with results from the model presented, a good linear outlet profile being obtained.

This paper presents and fully characterises a novel simplification approach for the development of microsystem based concentration gradient generators with significantly reduced microfluidic networks. Three microreactors are presented; a pair of two-inlet six-outlet (2-6) networks and a two-inlet eleven-outlet (2-11) network design. The mathematical approach has been validated experimentally using a purpose built optical detection system. The experimental results are shown to be in very good agreement with the theoretical predictions from the model. The developed networks are proven to deliver precise linear concentration gradients (R(2) = 0.9973 and 0.9991 for the (2-6) designs) and the simplified networks are shown to provide enhanced performance over conventional designs, overcoming some of the practical issues associated with traditional networks. The optical measurements were precise enough to validate the linearity in each level of the conventional (2-6) networks (R(2) ranged from 0.9999 to 0.9973) compared to R(2) = 1 for the theoretical model. CFD results show that there is an effective upper limit on the operating flow rate. The new simplified (2-11) design was able to maintain a linear outlet profile up to 0.8 microl/s per inlet (R(2) = 0.9992). The proposed approach is widely applicable for the production of linear and arbitrary concentration profiles, with the potential for high throughput applications that span a wide range of chemical and biological studies.

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