Sharif Digital Repository

Since plasma is rich in many biomarkers used in clinical diagnostic experiments, microscale blood plasma separation is a primitive step in most of microfluidic analytical chips. In this paper, a passive microfluidic device for on-chip blood plasma separation based on Zweifach–Fung effect and plasma skimming was designed and fabricated by hot embossing of microchannels on a PMMA substrate and thermal bonding process. Human blood was diluted in various times and injected into the device. The main novelty of the proposed microfluidic device is the design of diffuser-shaped daughter channels. Our results demonstrated that this design exerted a considerable positive influence on the separation... 

In this paper, the problem of content caching in 5G cellular networks relying on social-aware device-to-device (D2D) communications is investigated. Our focus is on how to efficiently select important users (IUs) and how to allocate content files to the storage of these selected IUs to form a distributed caching system. We aim at proposing a novel approach for minimizing the downloading latency and maximizing the social welfare simultaneously. In particular, we first model the problem of maximizing the social welfare as a many-to-one matching game based on the social property of mobile users. We study this game by exploiting users’ social properties to generate the utility functions of the... 

The improvement of the quality of the hole transporting layer (HTL) plays a key role in the fabrication of highly efficient and stable perovskite solar cells (PSCs). Here, we used rubrene as a surface treatment agent on top of a spiro HTL. We found that rubrene can cover the pinholes of the spiro layer and provide an excellent contact layer for planar PSCs. Based on this modification, mobile gold ions from the metal electrode are prevented from diffusing through the HTL hindering the degradation of PSCs. The optimized device shows a maximum power conversion efficiency (PCE) of 19.87% and a 79% fill factor (FF), which are higher than the 17.98% PCE and 72% FF of the reference device. In... 

The emergence of textile-based wearable sensors as light-weight portable devices to monitor desired parameters, has recently gained much interest and has led to the development of flexible electronics on non-rigid substrates. The flexible biosensors may result in improved sports performance, to monitor the desired bodies for injuries, improved clinical diagnostics and monitor biological molecules and ions in biological fluids such as saliva, sweat. In addition, they could help users with different types of disorders such as blindness. In this context, new composite and nanomaterials have been found to be promising candidates to obtain improved performance of the textile based wearable... 

For the first time, we present self-consistent solution of ultrathin body device structures to investigate the device parameters variation on the characteristics of nanoscale MOSFET. Our two dimensional (2-D) device simulator Is based on Nonequlibrium Green's Function (NEGF) forma lism. Starting from a basic structure (DG-MOSFET) with a gate length of 10 nm, variation of gate length, channel thickness, gate oxide parameters was carried out in connection with the numerical calculation of device characteristics. In this work Quantum transport equations are solved in 2-D by NEGF method in active area of the device to obtain the charge density and Poisson's equation is solved in entire domain of... 

Optical code division multiple access (OCDMA) is a promising multiple-access technique for future all optical networks. In this manuscript, the usefulness of exploiting bistable optical elements as threshold devices in coherent OCDMA systems is analytically investigated, in which the bistability effect is modeled by a simple square loop  

This study investigates the role of cell-cell and cell-ligand interactions in cytoskeleton organization of endothelial cells (ECs) and their directional migration within a microfluidic device. The migration of ECs in response to a biochemical factor was studied. Mathematical analysis of the cell migration pathways and cellular cytoskeleton revealed that directional migration, migration persistence length, migration speed, and cytoskeletal stress fiber alignment can be mediated by the level of cell contacts as well as the presence or absence of a biochemical polarizing factor. It was shown that in the presence of a biochemical polarizing factor, higher cell density and more frequent cell... 

This paper proposes a new coil structure for inductive powering to wearable/implantable biomedical devices. This structure is virtually independent from the direction (and alignment) of the receiving coil relative to the transmitting coil. In addition to conducting experimental tests and characterizations, the proposed coil structure (energized by a transmitting coil) has been used to power up a real test system designed for wireless neural recording, operating at 1.2V and drawing 48 mW  

Researchers are faced with huge challenges when undertaking BME research projects in developing countries. Various administrative, technical, economic and even cultural barriers have to be overcome whereas the quality and quantity of the output has to be comparable with the developed world in order to make results publishable. This paper uses a real project context to highlight the major problems and the necessity of a holistic approach which would take into consideration all stakeholders interests. It is only by tackling problems such as relationship between academia-industry and administration efficiency at their root that significant progress can be achieved  

Carbon-based sensors are attractive because of their excellent sensing capability. In this paper, we propose a new approach to analytically model the sensitivity of these devices based on graphene. The model relies on the surface potential and current of the device. For the first time, we included ionization in the modelling and examined the importance of this effect. In order to validate the model, the results are compared with experimental data from a fabricated device  

This paper investigates the dynamical behaviour of the fractional delayed damped Mathieu equation. This system includes three different phenomena (fractional order, time delay, parametric resonance). The method of harmonic balance is employed to achieve approximate expressions for the transition curves in the parameter plane. The n = 0 and n = 1 transition curves (both lower and higher order approximations) are obtained. The dependencies of these curves on the system parameters and fractional orders are determined. Previous results for the transition curves reported for the damped Mathieu equation, delayed second-order oscillator, and fractional Mathieu equation are confirmed as special... 

We proposed a modeling procedure to calculate the impact of temperature on the detection efficiency in photodetectors based on CdTe materials. Temperature increase impacts on the electrical properties of the materials such as carrier mobility and carrier recombination lifetime. This impact which can be effective in some cases has been normally ignored in the modeling approaches presented in the literature. Here we show that increasing the temperature from 190 K to 300 K not reduces the mobility of both electrons and holes but also significantly reduces the carrier lifetime. The result will impact on electric-field within the depletion width of the device, drift and diffusion lengths which... 

Execution speed seriously bothers application developers and users for wearable devices such as Google Glass. Intensive applications like 3D games suffer from significant delays when CPU is busy. Energy is another concern when the devices are in low battery level but users need them for urgency use. To ease such pains, one approach is to expand the computational power by cloud offloading. This paradigm works well when the available Internet access has enough bandwidth. Another way is to leverage nearby devices for computation-offloading, which is known as device-to-device (D2D) offloading. In this paper, we present Dandelion, a unified code offloading system for wearable computing. Dandelion... 

Background & Objective: A sensor network is composed of a large number of sensor nodes that are deployed to perform measurement and/or command and control in a field. Sensor nodes are battery powered devices and replacement or recharging of their batteries may not be feasible. One of the major challenges with sensory wireless networks is excessive energy consumption in nodes. Clustering is one of the methods that has been offered for resolving this issue. In this paper, we pursue evolutionary clustering and propose a new fitness function that har-nesses multiple propagation indices. Methods: In this paper we develop an efficient fitness function by first selecting the best clusters, and then... 

Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a... 

A superhydrophobic extractive phase was prepared and packed in a needle trap microextraction device for extraction of volatile organic compounds, followed by their determination by gas chromatography. The superhydrophobic phase was prepared by surface modification of melamine formaldehyde (MF) sponge embedded by reduced graphene oxide (rGO). The overall properties of the modified MF along with its high sorption capacity and low cost fabrication were indicative of its feasibility to be highly suitable for extraction of organic pollutants. The determined water contact angle (>150o) from the surface of melamine formaldehyde–reduced graphene oxide (MF–rGO) revealed its high affinity toward... 

The design and operation of a simple mechanical drive system, which is able to perform a fine course of angular motion, are reported. The system consists of a lead screw, a drive nut, sine bar legs, and an output shaft that can scan the optical holder mount. With a stepper motor coupled to the lead screw and interfaced to a PC, it is possible to control the scanning operation. When a 800 step/turn motor is used, it is possible to have an angular resolution of about 0.5 mdegree for a dynamic range of about 23°. The reproducibility of the results is about 0.22% for the scan angle and the hysteresis effect of the system is in the range of 1.71%. For a total scan of 51,200 steps, a scan angle of... 

In the investigations presented here, the feasibility of producing magnetic-nonmagnetic bimetals made of 316L/17-4PH and 316L/Fe powders by micro-metal injection moulding process (μ-MIM) was studied. In order to achieve sound replication of small specimens with dimensions less than 1 mm, very fine powders with mean particle sizes in the range of 3-7 μm were used. A wax-polymer binder system specially designed for micro-moulding was used to make up the feedstock. The isothermal and non-isothermal sintering behaviour of the moulded components was evaluated under hydrogen atmosphere. The effect of powder-binder-ratio of the feedstock, master alloy addition, and sintering conditions on the...