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Literature Review

The project is about microfluidics, our main focus is designing a microreactor for the purpose of dye degradation. First step was literature review. We searched about the importance of microfluidics, fabrication techniques, and materials. We made a short brief to report the findings of our research and the nature and challenges of the project, it was basically answers to a set of questions. I prepared it with my colleagues Batool Sayed Majeed and Mahmood Ashoor.

Title: Fabrication of a microreactor for dye degradation Abstract: This project aims to fabricate a microreactor to be used for dye degradation through the employment of Fenton reaction. Different fabrication materials and techniques are studied to choose the best technique among them. Additionally, the effect of different parameters on the reaction kinetics is examined. Background: Dye is one of the pollutants present in wastewater. It is important to find an efficient degradation method for dyes to be able to provide for the great demand of freshwater nowadays. Advanced oxidation processes (AOPs) are employed for that purpose, specifically Fenton reaction in our case. Dye degradation was investigated in different type of reactors, including but not limited to batch reactors. However, many issues were encountered. The use of a microreactor can resolve some of those issues due to its smaller molecular diffusion length. It eliminates the mass transfer limitation, consequently increasing the efficiency of degradation. The performance of the microreactor is dependent on different parameters, like the material of construction, fabrication method, and the dimensions of the microchip. Changing one of the aforementioned parameters can lead to a completely different outcome. Thus, it is critical to find the right optimization of those parameters, to reach the desired outcome, which is efficient dye degradation. The common materials that were investigated in literature for this specific application are polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA). There are many advantages to using those materials, including their low cost of fabrication, variety of fabrication techniques, and availability. Some of the fabrication methods examined for those materials are computer numerical control (CNC) machining, CO2 laser technique, photolithography, etching, and inject molding. CO2 laser technique can have an edge over the CNC machining, as the CO2 laser technique have some considerable advantages that the CNC lacks. Firstly, the CO2 laser is considered a non- contact process, where the beam is not physically touching the material but it is melting and vaporizing the material by the heat supplied from the beam. Secondly, due the prior statement as well, the CO2 laser has a lower chance of instrument damage leading to failure when compared to the CNC, as the CNC has a drilling bit which has a high probability of breakage if not treated well under the specified constrains as we are dealing with microsystems which elevate this probability due to the usage of very small drilling bit (rotations speed, feed speed and drilling speed (depth)). In addition, the CO2 laser is considerably safer as it is performed in a confined area and there is no direct contact like the CNC. Both methods precision could be considerably equal but the CNC might ensure some errors caused by a defect in the drilling bit (physical defect). However, we need to ensure several aspects to keep the privilege of the CO2 laser over the CNC, as we need to ensure that the melting and vaporizing of the materials is not causing blockage of the channels due to the residuals of the material caused by the heat supplied. And the vaporized materials should not effect the lenses used in the instrument so we need to make sure that the vaporized materials are not defecting the lenses which might lead to inaccuracies. Finally, there should be further investigation with regards to the shape of the channel as the most common channels are rectangular, which need to be incorporated with the utilized fabrication method. Question: We aim to find the most efficient material along with its fabrication method for dye degradation. We want to find a method for fabrication that can be mimicked and duplicated accurately, hence can be used for mass production. Method: First, getting familiarized with the different aspects of microfluidics, fabrication techniques and materials, by reading research papers and journals. Then, exploring the fabrication machines available in Fab Lab, specifically CNC machine, and CO2 laser technique. Why is it significant? The reaction kinetics are highly affected by the material, fabrication method, and the dimensions of the microreactor. Therefore, it is critical to optimize those parameters to achieve the best results.

References: S. Das and V. C. Srivastava, Photochem. Photobiol. Sci., 2016, DOI: 10.1039/C5PP00469A Ap Lazer

Last update: August 23, 2021