Sharif Digital Repository

Skin tissue engineering, is considered as a method to heal full-thickness wounds. The basis of this method is fabrication a substrate named scaffold in order to replace the lost skin tissue temporarily. The aim of the present study is the fabrication and characterization of skin scaffolds using two natural polymers, which are Chitosan and Gelatin. This study is divided into three phases: first is the investigation of the influence of two cross-linkers named Glutaraldehyde and a kind of carbodiimide on the properties of scaffolds, second is the characterization of scaffolds fabricated by three different ratios of chitosan/gelatin and third is the evaluation of the effect of Allantoin on... 

The heart is a powerful muscle whose primary function is to pump blood into the body. many cardiac patients reach a stage that can no longer be kept function of their heart to a satisfactory level by using medication thus doctors undergo surgery. The common problem occurs to most patients undergoing cardiac surgery is that after the surgery, the patient's heart during a short period of time is unable to supply blood with the flow rate and pressure required for all organs, especially the end organs of the body. In this conditions, ventricular assist device help the patients. These devices are used parallel with patient’s heart and supply the large portion of blood that patient’s body needs.... 

With the advent of new computer technologies, computational analysis on the human organs has become tremendously popular in the field of medical science. Every year thousands of people suffer irreversible eye damages pertaining to lack of adequate medications. In this regards, enormous amount of money is spent annually but mostly in vain due to the irreversibility and silent nature of eye diseases like glaucoma. Yet more precise studies on the topic are requisite. In this thesis, a validated half 3D finite volume model of human eye considering the fluid flow in collaboration with heat transfer in the steady state utilizing the well known discretized bio-heat transfer equation coupled with... 

Articular cartilage Function is vital to joint tasks and its motion. The main biomechanical tasks of articular cartilage are a) the distribution of loads occurred in joints; b) providing joints with frictionless surface. The particular mechanical properties of articular cartilage make it possible for the Cartilage tissue to do its duty successfully. The biological factor that causes articular cartilage to damage is still unknown. It is believed that mechanical factors are the main reason for the cartilage destruction in osteoarthritis. Factors like age, heavy exercises and impact can begin tissue destructions and result in change in mechanical properties. To study the process of the... 

Micro-Structures, especially cylindrical shells, has been widely used in different high tech industries, that this extreme usage emphasis, analyze of the vibration behavior of these structures. For gain an appropriate characteristics for a known purpose we can stiffen cylindrical shells with some rings that lids to improvement in mechanical properties of them. With advent of new materials, such as Functionally Graded Materials (FGM) and unique properties of these materials investigation of vibration behavior and characteristics of micro cylinders which has been made of FGM can be very important and essential. By using FGM materials many mechanical characteristics of these structures can be... 

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... 

In femoral neck fracture when the non-union happens in the fractured zone, valgus osteotomy is a surgery method to overcome bone non-union. In this method, a wedge osteotomy-with specific depth and angle- at the femoral neck is created. By changing the bone angle at the fracture site and the angle of the wedge osteotomy it is desired to convert the shear stress to the normal stress. Clinically it is believed that this would facilitate bone healing and prevent bone fracture. This surgery method also changes the anatomy of muscles due to changing hip anatomy, joint reaction force , and it’s direction. This procedure while minimizing shear stress it also reduces the blood supply to the area and... 

Metallic implants are often used in the open reduction and internal fixation of fractures. Open reduction and internal fixation are commonly used in cases of trauma when the bone cannot be healed using external methods such as casting. The locking compression plate combines the conventional screw holes, which use non-locking screws, with locking screw holes, which use locking head screws. This allows for more versatility in the application of the plate.
In the present work, the stress (von-mises) and deformation of a locking compression plate fixed across a transverse fracture (2-mm gap) at the midshaft of femur was evaluated by Ansys software. Femur model is divided to two part... 

Researches in last decades have shown that biological cell’s functionality is related to the way of their deformation in response to forces and stresses exerted on the cell. Therefore designing microsensors with easy and economical applicationswhich are capable for determining cell mechanical properties seems to be logical. In this project using an electrostatically actuated microbeam with both clamped ends equipped with an indenter at midpoint to transmit force on the cell, proposed as a technique to apply axial load on the cell. Inthis research by implementation of approximated methods for solving nonlinear algebraic and differential equations, governing on microbeam deflection, it has... 

Most elderly and physically disabled people suffer from lack of functionality and dexterity in their elbow or wrist. These disabilities are due to the damages mostly caused by sport surgery, spinal surgery, or stroke. Therefore, design of an assistive exoskeleton robot for upper limb movements seems necessary. The purpose of this study is to design, fabricate and deliver a control algorithm for an assistive wearable robot. The robot has three degrees of freedom in order to help the flexion/extension of elbow and wrist. Dynamic and kinematic model of elbow, forearm, and wrist is developed to determine the amounts of torques which are required in the joint actuators mounted on the robot.... 

In this project a centrifugal, microfluidic platform to the end of separation and studying circulating tumor cells is designed, modelled and analyzed. Circulating tumor cells (CTCs) are specific types of cancer cells which leave the original tumor and enter the blood stream. For the separation of CTCs, a novel anti-body separation technic has been used which targets the specific MCF7 CTCs using their corresponding Ep-CAM antibody. First the Ep-CAM antibody is coated on magnetic nanoparticles through a chemical bonding process. Afterwards the CTCs are exposed to their antibodies, through which they will bind together and form CTCs with magnetic characteristics. Finally through exerting an... 

Actin is the most abundant protein in most eukaryotic cells. It is highly conserved and participates in more protein-protein interactions than any known protein. Actin plays a crucial role in cell motility, adhesion, morphology and intracellular transport. Its biologically active form is the filament (F-actin), which is assembled from monomeric G-actin. In this thesis, the mechanical properties and characteristics of both G- and F-actin are studied using molecular dynamics simulations. In general, this thesis can be categorized into two individual parts: First, steered molecular dynamics simulation was performed to assess tension of monomeric G-actin molecule, and stress-strain curves were... 

Numerous studies have shown a direct relationship between skeletal muscle active force and intracellular calcium ion concentrations; In fact, no matter how the muscle is stimulated (neurological, electrical, chemical, and mechanical stimuli), the main cause of muscle activation and consequently force generation is calcium ions.According to this scientific finding, the purpose of this study is to present a new chemo-mechanical multiscale model of skeletal muscle based on the fundamental principles of continuum thermodynamics. In this model, unlike other similar studies, muscle active force is not considered as the conventional multiplication of isometric force in a set of corrective... 

Liver is the largest internal organ of the human body which serves many vital functionalities. Recently, liver-on-a-chip systems have been used to model some of the vital liver specific-functions and to investigate its related diseases. The purpose of the present study was simulation of some of these liver specific functionalities on-a-chip and using the obtained results in predicting hepatocellular functionalities i.e. production of some metabolites and modeling some of the liver-related diseases which have been done numerically and experimentally. Numerical simulations have been developed in two-dimensional and three-dimensional forms. In the 2D simulation, the governing equations i.e.... 

Spine is one of the most important musculoskeletal systems of the human body. Any problem which is related to this part of human body causes pain and disability. Spinal compression forces are one of the main reasons of this disability and pain. It is assumed that intra-abdominal pressure causes spinal unloading in lifting. Studies usually don’t consider the role of intra-abdominal pressure and introduce it as an effective parameter which can increases spinal stability and influences spinal mechanics.Generation mechanism of intra-abdominal pressure remain enigmatic, studies that advocate the unloading effect of IAP usually consider a raise in IAP to be primarily due to the activity of... 

One of the most important parts of oil industry is drilling with rotating drillstrings. In a drillstring because of the contact between bit and formation, contact between drillstring and borehole wall, existence of drilling mud, misalignment in drillstring and stick-slip phenomenon; axial, lateral and torsional vibrations is created. These vibrations may lead to fatigue failures and abrasive wear of tubular, damaging the drill bit and borehole wall. In this thesis the drillsting vibrations is studied using finite element method. To this end, cylindrical superslement with C1 continuity is presented. By using the shape functions of this superelement; kinetic and potential energy of drillstring... 

Red Blood Cells (RBCs) are the main cells in human blood with a main role in mechanical properties of blood as a fluid. Several methods are developed to simulate the behavior of RBCs motion and deformation in micro-capillaries. Since in microscopic scales, using discrete models are more preferred than continuum methods, moving particle semi-implicit method (MPS) which is one of the recent innovative particle based methods, can simulate micro-fluidic flows based on Navier-Stocks equations. Although by the recent developments MPS method has turned into a considerable tool for modeling blood flow in micro-scales, but still some problems, such as commitment to use small time steps, restrict the... 

Surgical simulation systems facilitate a safe and efficient training process by providing a virtual environment in which the trainee can repeat the surgical procedure unlimitedly at different situations. The present study attempted to provide a real time simulation for the grasping procedure of a large internal organ during laparoscopic surgery. A mass-spring-damper model was employed to simulate the nonlinear viscoelastic large deformations of spleen tissue interacting with a triple-jaw large organ grasper. A novel collision detection algorithm was designed and implemented to determine the contact points between the tissue and the grasper jaws. The boundary conditions imposed at the contact... 

This research is concerned with the study of the static, dynamic, vibration and instability of an electrostatically actuated microbeam gyroscope considering geometric nonlinearities and electrostatic fringing fields. A vibrating microbeam gyroscope consists of a beam with a rigid (proof) mass attached to it and undergoes coupled flexural-flexural vibrations coupled with base rotation. The primary oscillation is generated in drive direction of the microbeam gyroscope by a pair of DC and AC voltages on the mass. The secondary oscillation occurring in the sense direction is induced by the Coriolis coupling caused by the input angular rate of the beam along its axis. In this case gyroscope acts... 

Nowadays cancer has become one of the main and prevailing worldwide challenges in medical field, and many attempts have been made for treatment of this disease. The common methods for cancer treatment, have had significant side effects and even resulted death. The method of “High Intensity Focused Ultrasound” (HIFU) as a non-invasive method, has been welcomed by engineers and doctors and is using in some tumor based cancers. For predicting the level of temperature increasing in tissue, it’s necessary to model the ultrasound waves propagates from HIFU source precisely. The main object of this thesis is modeling and simulation of the behavior of ultrasound wave propagation and investigating...