Sharif Digital Repository

Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion.... 

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... 

Improving efficiency of heat exchangers has always been an important concern for the industry. Pulsating heat pipes are novel and efficient technology in the field of heat transfer. Pulsating heat pipes are widely used in solar water heaters, solar desalination systems, air conditioning systems, cooling of electronical boards, etc. these applications explain the necessity of performing this study in our country. In this research, thermal performance of open loop pulsating heat pipes using two operating fluids (ferrofluid with surfactant and aluminum microfluid) is experimentally investigated. Start-up and steady thermal performance of pulsating heat pipes charged with these two operating... 

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... 

Design, simulation, optimization and manufacturing of an enzyme-based microfluidic biosensor has been carried out during this research to measure histamine concentration in a sample. The designed biosensor is composed of a micro-bioreactor to degrade histamine and yield hydrogen peroxide, and a chemical reactor to measure the amount of hydrogen peroxide, using chemiluminescence methods. The geometry of the bioreactor and chemical reactor is developed through comparison and optimization of several different geometries. In theory, the designed sensor can determine histamine concentration in a range of 10M to 1mM under one minute, with a maximum error of 5%. Designed biosensor is built using... 

Continuous separation processes in microfluidic devices experienced a steep rise in attention during the last two decades. Among the different separation processes, liquid-liquid extraction especially benefits from the short molecular diffusion distance and large specific interfacial area, as these are advantageous for effective mass transport. In the present study, glass-based microfluidic devices have been fabricated utilizing laser ablation and wet chemical etching methods then experiments and numerical simulation were carried out to investigate hydrodynamic behavior of fluid flow in Y-junction microfluidic. In order to achieve phase separation at the end of the microchannel, a phase... 

The advent of microfluidics as suitable environments for culturing cells is associated with some challenges such as shear stresses applied on the cells. In fact, hepatocytes lose their function as exposed to high shear stresses similar to other cell types. Moreover, among all factors needed for cell viability, feeding hepatocytes with adequate oxygen is of great importance due to their high demand for oxygen compared the other cells. In this thesis, different types of cultures including 2D and 3D has been used in order that shear stresses would be in allowed range and provision of hepatocytes with sufficient oxygen concentrations has been ensured as well. In addition to supplying hepatocytes... 

Diabetes is one of the most catastrophic diseases in the world. There will be an end to patients’ problems if scientists can invent the artificial pancreas, but there is no implantable sensing core available. All of the sensors used for measuring blood glucose level were based on an electrochemical sensor which will generate a glucose level dependent electric current. The chemical structure of that sensor will deny its usability for in vivo applications. By exploring several biological and electrical literatures we introduced a fully electrical method for sensing the blood glucose level by impedance measurement. In this thesis we introduced a new method for sensing the blood glucose... 

Separating cells from a mixed sample is a required task in biotechnology and modern medicine, for example to isolate CTC’s that are of interest for doing therapy and diagnosing or doing research. A minute percentage of target cells must be separated from a large amount of unwanted cells. These target cells like CTC’s could be as rare as 1 target cell per millions of unwanted background cells. Hence Microfluidic cell sorting schemes based upon fluorescent labelling, electrophoresis, dielectrophoresis and magnetophoresis have been devised. Microfluidic magnetically-activated cell sorting (MACS) does not need any optical instrument or current source and electrode. By using an electromagnet or... 

A Lab-On-a-Chip (LOC) is a device which can integrate one or many laboratory functions on a small chip with millimeters to few square centimeters in size. LOC is a subset of MEMS devices and known as “Micro Total Analysis Systems” (µTAS) as well. LOC technology is closely related to microfluidics which primarily describes the physics, manipulation and study of minute amount of fluids.In this research we tried to simulate the performance of a microfluidic device for counting blood cells to find main factors of it for design and manufacturing. This research has two main sections, hydrodynamics of fluid inside the microchannels and finding electrical performance of designed Coulter counter for... 

Circulating tumor cells (CTCs) are cancer cells which shed from the primary tumor, enter circulation and spread cancer all over the body. CTCs give valuable information about cancer and can help diagnosis and prognosis. Hence separating and isolating CTCs from blood is a necessity for cancer therapeutics. CTCs are separated from blood cells by their different physical or biochemical properties. Many groups have attempted different methods for separation of CTCs. Inertial microfluidics is one of the newest approaches in CTC separation technologies which separates CTCs based on their size. Current inertial microfluidic systems containing straight, spiral, serpentine and contraction expansion... 

The first attempt of this study was theoretical and experimental investigations of bioelectrochemical processes in microfluidic systems. Besides, novel applications of this technology as a powerful platform for maximum usage of bioenergy were introduced. The feasibility of a microfluidic microbial fuel cell (MFC) as an efficient power generator for production of bioelectricity for implantable medical devices (IMDs) and fabrication of microfluidic microbial electrolysis cell (MEC) for hydrogen medicine were investigated. For the glucose-fed microfluidic MFC, the maximum power density of 5.2 µW cm-2 obtained in this study is 13 fold greater than the power density reported previously for... 

All the biological diagnostic devices that are introduced to the consumers, must meet WHO criteria. Some of these criteria include being affordable, sensitive and deliverable to the user. In the last twenty years, there have been lots of efforts to use microfluidic devices for biological assay. Due to their expensive price and requirement of complex equipment for their fabrication, polymer-based microfluidic devices have not been able to be used in developing countries. It is to be hoped that introduction of paper for fabrication of microfluidic devices could make microfluidic devices meet WHO criteria. μPADs are divided into well-based and channel-based devices. In the present work, both... 

Microfluidic is a science and technology in which they study the behavior of fluids, control them and design devices or systems with dimensions of tens to hundreds of micrometers. The technology has the ability to design and manufacture macro-scale and micro-scale equipment, such as micro-pumps, micro-valves, micro-filters, micro-mixers, micro-reactors, and other equipment. The benefits of this technology include the use of low sample size, low waste of energy, low power consumption, short response time, high system performance, portability and performance of several operating phases in a compressed piece such as production, isolation and analysis. Also, the very low amount of chemicals and... 

In this project, two centrifugal microfluidic platforms with the goal of separation and genetical study of circulating tumor cells have been designed, simulated and fabricated. Circulating tumor cells are the ones that are detached from the cancer tumors, entered the blood and disseminated the danger of cancer through other parts of the body. Both passive and active methods of separation are investigated in this study. The passive method is based on the inertial effects of the fluid and the active method is based on the magnetophoretic force exerted from an external magnetic field. In order to use the active method, the magnetic nanoparticles are attached to the breast cancer cells by the... 

Diabetes mellitus is a global endemic that is rapidly increasing prevalence in both developing and developed countries. Recently, the American Diabetes Association has recommended the hemoglobin A1c as a possible substitute to fasting blood glucose for diagnosis of diabetes because it is an indicator of long-term glycemic control. Also, centrifugal microfluidics systems have a good potential to be used in the point of care testing systems. In this study, two centrifugal microfluidic discs were designed and manufactured in order to separately measure the hemoglobin and hemoglobin A1c in the whole blood. In the first part of the study, the hemoglobin measurement disc consists of two chambers... 

Renal diseases and consequently kidney failure is one of the important death factors around the world in recent years. It causes hundreds of thousands die every year and is in progress. Researchers believe that increasing chemical and nonchemical materials density in the blood which is the air pollution, use of tobacco and other parameters cause renal cells misfunction in urine filtration and regulation of blood pressure. The goal of this work is design and fabrication of a microfluidic device which provides different cell types to be cultured and imposed pressure. To do this, a high throughput microfluidic device is needed to mimic kidney biologically. Having such a device helps to analyze... 

Cell lysis, as the first procedure of cell pretreatment, is a process that breaks cell membranes open thereby facilitating access to intracellular substances, such as DNA, proteins, and other components for further analysis to diagnose and treat diseases at early stages. Currently, there are several methods for cell lysis at macroscales. However, the time-consuming and expensive procedures as well as the large scal of the system are the main disadvantages of the systems. Recently, microfluidic systems have attracted considerable attention due to advantages associated with automation, integration and miniaturization of biomedical test protocols. Centrifugal microfluidics (Lab-on-a-Disc) is a... 

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... 

Due to the increasing need of use of drugs and insufficient efficiency of conventional methods, drug delivery systems has gathered a lot of interests. There are different systems existing for controlled drug delivery, among which is implementation of hydrogel microparticles (microgels) as carriers with high potential. The most important factor in these systems is size distribution of drug-carrying microgels and a narrow size distribution leads to a controlled and suitable release. Due to unique characteristics of microfluidic systems, significant focus has been placed on them nowadays for production of microgels with suitable morphology and narrow size distribution. Therefore, in this study...