Sharif Digital Repository

Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors... 

In recent years, there have been huge advancements in fabrication of micron-sized devices such that they enabled engineers to create a wide range of miniaturized systems, each of which is utilized in mechanical, electrical, and thermal applications. Micromixers are one of these devices with the role of mixing various micro flows. These devices are broadly used for chemical, biological, and biomedical assays. Among variety of micromixers, one that employs electrokinetic transport phenomenon is of great popularity. For instance, mixing under electroosmotic flow enables accurate process control and eliminates the need for moving components inside micromixer. The very complex nature of electric... 

Nowadays, microfluidic flow appears in many applications, such as medical, biological, and chemical industries. Where as, micromixing, which deals with mixing of microfluidic flow in micro channels, appears to be an important issue to many researchers. In such systems, molecular diffusion plays an important role. On the other hand, lattice Boltzmann method is a relatively new simulation technique for complex fluid systems and has become interesting to many researchers in computational physics. In this study, computational simulation of such mixing process, using LBM is the main objective. Different obstacle layouts inside a microchannel have been investigated. Chaotic advection and jet... 

Numerous applications of Lab on a Chips (LOCs) in chemical/biochemical analyses as well as the emergence of advanced methods for their manufacture attracts many researchers’ attention to these micro instruments. Low sample volume consumption and their high controllability are accounted as the main advantage of LOC systems. Micromixers are among the main components of any LOC in which mixing and/or reaction among two components occur. Micromixers have many potential applications in biological and medical sciences, and so they are repeatedly charged by biofluids. Due to sensibility of biofluids, to avoid disintegration, applying electroosmotic flow instead of pressure-induced flow has priority... 

Recent advances in micro-technology are finding important applications especially in chemical and biological processes. In these applications, mixing has a profound importance. Due to the inherent low Reynold’s number flow in micro systems, diffusion mixing is the dominant mixing mechanism at these scales. This is in contrary to the high Reynold’s number ordinary applications where turbulent mixing plays the major role. There are two major classes of micro-mixers: passive and active. Passive micro-mixers rely on geometric features to enhance mixing. Active micro-mixers on the other hand, use external excitation to promote and control the rate of mixing. In this work, using numerical tools,... 

The “Lab-on-a-Chip” is a micro-scale device which uses fluids as working medium and can handle number of functions such as sample preparation and transfer, separation, bio-sensing and detection. One of the important parts of these devices is micro-mixer, that should blend two fluid species in a short time with desirable mixing quality. Micro-mixers are classified as passive and active. By considering the micro-scale of mixers, turbulence phenomena cannot occur due to dominance of viscous forces, therefore the mixing only depends on molecular diffusion. This thesis consists of two main parts, in the first part algebraic multigrid has been studied and implemented in Rayan (in-house CFD code).... 

The purpose of this study is to study heterogeneous nanocatalysts for the production of biofuels by the method of exchange of styrene using oil and methanol as a fossil fuel alternative. Preparation of nanocatalysts, performing characteristic tests and investigating the reaction in different operating conditions in the batch reactor has already been studied. Therefore, in this study, the production of biodiesel fuel using the trans-esterification of canola oil with nanocatalysts in the micro-reactor reactor will be discussed. Previously, a heterogeneous catalyst (lithium based on calcium-lanthanum) was constructed using a co-incineration method and a wet inoculum, and as active and stable... 

Lab-on-a-chip devices have gained a lot of attention in chemical and biomedical analyses during the past two decades. These devices employ microfluidics basics and fundamentals to combine multifold laboratory processes in one single portable chip. The electric field has been often used in most microfluidics applications for the ease of sample control as well as become easily integrated to other chip components. Instabilities in microflows would occur when two fluids of different electric properties are exposed to an adequately strong electric field. Studying these electrokinetic instabilities is not only important for the fundamental studies but also for practical applications in micromixers... 

Cancer is a major cause of mortality worldwide, with a disease burden estimated to grow over the coming decades. Circulating tumor cells (CTCs) are rare cancer cells released from the primary or metastatic tumors and transported though the peripheral circulatory system to their specific secondary locations. The presence of CTCs in a cancer patient’s blood has been used as a prognostic biomarker, with lower CTC count correlating with greater overall survival. In spite of its clinical potential, the isolation and detection of CTCs has been a challenging task due to its rare presence amongst other blood cells (as low as 1–10 CTCs per billions of blood cells) and variability in terms of both... 

Nowadays, intracellular studies have been widely developed in biological applications. Intracellular analysis requires direct experiments on cells such as cell separation, purification, lysis and DNA extraction. The process of cell lysis and the resulting DNA purification is a crucial step in diagnostic processes. Since, the basis of many genetic studies is the information existed in double-stranded DNA structures.In this project, a microfluidic system is presented which performs integrated chemical cell lysis and DNA extraction. The cell used in this study is L-929. In order to increase cell lysis, the serpentine micromixer in combination with internal and external barriers at the beginning... 

Nowadays, the use of microreactors is receiving a great deal of attention due to the unique characteristics of such systems, such as high surface-to-volume ratio, low material loss, greater safety, and minimizing mass and heat transfer limitations. In this study, the optimization of the continuous-flow synthesis of Plavix by Cu-MOF heterogeneous catalyst utilizing a glass microreactor was investigated. Structural characteristics of the catalyst were investigated using X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and BET surface area studies to describe the structure and morphology of the catalyst. In order to build... 

In the past decades, the production of various active pharmaceutical ingredients in batch processes was common. But today, the approach of pharmaceutical companies has changed and the use of the equipment and continuous processes such as microreactors has become common for reasons of safety, better mass and heat transfer, reduction of operators, and ease of scale-up. Unlike many top-selling drugs such as Ibuprofen and Artemisinin, Clopidogrel, the world's third best-selling drug needed by cardiac patients, has been manufactured only in batch processes. Due to the increase in the average age of the population, the urgent need for the use of Plavix (clopidogrel) has increased in recent years.... 

Clopidogrel, as an antiplatelet medicine, is currently one of the most widely used medicines to reduce the risk of stroke and prevent the formation of blood clots for heart patients all over the world. This medicine is still produced using the conventional approach of drug production, i.e. batch method. On the other hand, due to the many advantages of flow chemistry, such as increasing the rate of mass and heat transfer, increasing safety, performance, etc., the production of medicines using the flow approach has been highly regarded by large pharmaceutical companies in recent years. In this research, the production of clopidogrel was done using a continuous flow approach and different... 

In order to fabricate batch and continuous systems to synthesize Pirfenidone (PFD), Solidwork and COMSOL software were used. Effects of parameters on reaction yield including; microreactors, micromixer, solvents, temperature, reaction time, and catalysts were understudied. Moreover, FTIR, NMR and HPLC analyses used to evaluate the prepared PFD. Its yield in microfluidic (30.5 %) was higher than that of batch (17.1 %) reactor. Besides, reaction yield in the presence of DMSO was higher than DMF in both reactors. It was shown that, adding a micromixer enhanced reaction time. leading to a higher PFD yield. Nonetheless, the yield was reduced by enhancing the temperature when DMF was utilized....