Sharif Digital Repository

Nowadays Lab-on-a-chip systems are being widely used in medical applications, especially in analyzing minute volumes of blood for diagnosis and treatment of some crucial diaseses like diabetic. A Lab-on-a-chip is comprised of a variety of components such as micromixer, microdispenser, detection and separation units and so on. In this thesis, however, we have analyzed and numerically simulated a microdispenser which is electrokinetically driven. In other words, electrical potentials are applied to electrodes in order to conduct two fluids within a cross microchannel, and distribution of a sample fluid takes place due to appropriately applied potentials. In order to analyze and simulate the... 

The lab-on-a-chip (LOC) devices utilizing electroosmosis for flow actuation are usually encountered with non-Newtonian behavior of working fluids. Hence, studying the flow of non-Newtonian fluids under an electroosmotic body force is of high importance for accurate design and active control of these devices. In this thesis, mixed electroosmotically and pressure driven flow of salivathrough a rectangular microchannel is examined utilizing two viscoelastic constitutive equations, namely PTT and FENE-P models. Since the hydrodynamic entry length is usually negligible for microflows, a hydrodynamically developed flow is considered in the analysis. The governing equations in dimensionless form... 

Most of the current literature on the simulation of the electro-osmotic flow in micro-channels decompose electric potential to two components; internal and external potentials. They usually approximate the near wall changes in the ion concentration (called double layer) which is physically responsible for electro-osmotic force by a model (like Poisson equilibrium distribution or Debye-Huckel approximation). There are reports in the literature which show that the approximations lose their fidelity for more complex situations. In this thesis we solve the full system of Nernst-Planck and Navier-Stokes equations by resolving electric double layer. The proposed... 

A Lab-On-A-Chip is a micro-scale system whic h utilizes some micro-scale components in order to implement detection tests on samples. One of the most important components of a lab-on-a-chip device is the micro-mixer, which is responsible for appropriately mixing of samples in a short period of time. The biggest problem relevant to mixing in micro scales is that since as the viscous forces are dominant in micro scale and dimensions are small, it is impractical to mix fluids via turbulence, and consequently mixing process is performed by diffusion mechanism. Two major strategies are being used in order to improve the mixing performance and two groups of micro-mixers, passive and active types,... 

Lab-On-A-Chip is a micro-scale system which utilizes specific tools in order to operate detection tests on samples. One of the most important components of these devices is micromixers which is responsible for appropriate mixing of samples in short period of time. The biggest problem associated to the mixing in micro-scale is the regime that the flow takes during the process. Due to the small dimensions of micromixers the induced flow stream resides in the range of laminar flows and consequently the mixing is conducted solely by diffusion mechanism which is either time-taking or requires long micro-channel that causes the high cost of fabrication. In order to improve the mixing process two... 

This is a theoretical study on heat and mass transfer in electrokinetically driven microfluidic devices with particular consideration to the lab-on-a-chip (LOC) applications. Special attention is given to disclose the effects of the fluid rheology and the aspect ratio of the rectangular geometry on the surface reaction kinetics and the temperature rise due to the Joule heating. Along this line, two different viscoelastic constitutive equations namely PTT and FENE-P models along with the power-law viscosity model are being considered. The secondary aims also include exploring the influences of the fluid properties variations throughout the channel cross section on the hydrodynamic and thermal... 

Cancer is one of the most causes of mortality in the world. Leukemia is a type of cancer initiated by the rapid proliferation of blood cells including WBCs, RBCs, and Platelets, that classified into four general types of AML, ALL, CML, and CLL. The main treatment of leukemia is chemotherapy. Because of many problems that patients have with this treatment and not so good results of chemotherapy, we design a microfluidic chip that can perform personalized medicine treatment for leukemia patients.This microchip consists of two main parts, Concentration Gradient Generator (CGG), and cell culture. CGG system is a tree CGG with two inlets and four outlets, which makes a linear concentration of... 

Discovering new medicines and generally medical researches, are time consuming and expensive. But recent achievements in cell culturing methods and micro and nano-engineering techniques have enabled the researchers to investigate new medicines in a lesser time and price. Huh et al. successfully fabricated the lung on chip device. This device is consisted of three chambers. The middle chamber is separated in two equal parts and side chambers were considered in order to apply normal breathing. Periodic deformation was needed to apply the natural condition of cultured cells by expansion and contraction. Numerical simulation was needed to investigate the properties of flow in this kind of... 

In many microfluidic devices, focusing particles into a narrow stream is usually an essential step prior to counting, detecting, and sorting them. By installation of microfluidic laboratory functions on a rotating disk, new devices called Lab-on-a-disks, which have plenty of advantages in comparison to ordinary Lab-on-a-chips, shape. In this study, to the best of our knowledge for the first time, a Lab-on-a-disk device is designed and fabricated in order to focus particles prior to detecting them by a conventional CD-ROM as a strong optical system. Hydrophoresis method, using slanted obstacles to induce transverse pressure gradients, is utilized to focus particles. In this regard, the... 

The recent breakthroughs in the lab-on-a-chip technology will not be directly used as clinical devices unless the specific applications are carefully tested and certified. As there is a growing trend towards microfluidic devices for biomedical research, an active microfluidic device was developed. Common microfabrication methods were used to develop a microchip to separate and concentrate live and dead cells based on the dielectrophoresis phenomenon. Unique capabilities of the dielectrophoresis phenomenon make it a powerful tool for micro particle manipulation in micro scale. In this research, geometry for the mentioned purpose is designed and optimized. Three-dimensional microelectrodes are... 

Nowadays, due to the growing need of the human to further improve the health of the community, research in the field of pharmacology as well as simulation of the cell culture environment is increasing. One of the most important requirements for simulating cell culture is the use of concentration gradient in culture media. The reason for this is the dependence of cellular activity on the presence of a gradient of concentration in the environment. Also, in drug investigations, in order to speed up the examination of different drugs and reduce the amount of drug that will used, different concentrations of the drug should be considered simultaneously in the microchips. Therefore, to make the... 

% of human blood makes up of plasma, that this plasma is a rich source of proteins that can be used as biomarkers for a variety of clinical diseases and laboratory research, therefore, it is necessary that the plasma be separate by a high purity percentage. Using a centrifuge It is a common method used to separate plasma from blood, but because it requires large equipment and a large volume of blood, as well as stress caused by centrifugal force, increases the probability of damage to the biomarkers, so it has been tried today that Use methods that are easy to transport and require a small amount of blood. The idea of using the microfluidic device has been put forward for the purpose of... 

In this research, the ability of artificial intelligence to improve the biosensor performance of a microfluidic system has been investigated. Coulter counter is a microfluidic system that measures the concentration of particles in a fluid using signals obtained from a biosensor. The method of this system is called " Resistive Pulse Sensing (RPS)" method. The pulses in the Coulter counter signals are affected by the number, shape, size and speed of particles passing through the orifice. The pulse of two particles of the same size and different shape in these systems are very similar and this makes it difficult for an operator to distinguish the type of particle. Another disadvantage of...