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lithography
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Design and Implementation of a Scratching Nanolithography System
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor)
Abstract
Today, in order to reach atomic scale resolution, novel nanolithography methods, known as unconventional nanolithography, have been presented, since conventional methods, including photolithography and scanning beam lithography are fundamentally unable to fulfill this need. In this work, a specific type of unconventional lithography, known as scanning probe lithography, is presented. Scanning probe lithography takes advantage of the interactions between a very sharp probe and the sample in nanoscale distances to control this distance, and hence enable the modification of the sample using this sharp probe. In mechanical scanning probe lithography, the probe is used mechanically to change the...
Numerical Simulation and Analysis of Micro Nanoelectrodeposition
,
M.Sc. Thesis
Sharif University of Technology
;
Saeedi, Mohammad Saeed
(Supervisor)
;
Kazemzade Hanani, Siamak
(Supervisor)
Abstract
Nowadays, nanotechnology has emerged in many processes; hence the construction of this scale is also important. By reducing the size of equipment, raw material consumption is reduced and less space is needed for equipment. In addition it is economical. LIGA method has the potential to make parts with small dimensions and accurate tolerances, that it is impossible with other methods (chemical vapor deposition, physical vapor deposition, bulk micromachining, surface Machining). It is possible to assemble the pieces by producing micro-molding in LIGA procedure.In this thesis, numerical simulation of electrodeposition that is one of the main steps in the LIGA procedure has been investigated. One...
Emerging bioengineering strategies for regulating stem cell fate: Scaffold physical and biochemical cues
, Article Tissue Engineering: Current Status and Challenges ; 2022 , Pages 125-156 ; 9780128240649 (ISBN) ; Mashayekhan, S ; Sharif University of Technology
Elsevier
2022
Abstract
Stem cell therapy has been introduced as an emerging approach for injured tissue regeneration. This chapter addresses developing regenerative medicine techniques for controlling stem cell behavior. Recent studies have been reviewed and novel approaches have been divided into four main categories: 3D bioprinting, lithography, microfluidics, and electrospinning. Moreover, the impact of applied biophysical and/or biochemical cues to the designed scaffold on controlling stem cell activity has been discussed. The potential of using stem cells for various soft and hard tissue regenerations has been explored in different bioengineered scaffolds and the applied techniques for controlling stem cell...
Design of a hybrid inertial and magnetophoretic microfluidic device for ctcs separation from blood
, Article Micromachines ; Volume 12, Issue 8 , 2021 ; 2072666X (ISSN) ; Shamloo, A ; Akbari, J ; Sharif University of Technology
MDPI AG
2021
Abstract
Circulating tumor cells (CTCs) isolation from a blood sample plays an important role in cancer diagnosis and treatment. Microfluidics offers a great potential for cancer cell separation from the blood. Among the microfluidic-based methods for CTC separation, the inertial method as a passive method and magnetic method as an active method are two efficient well-established methods. Here, we investigated the combination of these two methods to separate CTCs from a blood sample in a single chip. Firstly, numerical simulations were performed to analyze the fluid flow within the proposed channel, and the particle trajectories within the inertial cell separation unit were investigated to...
The effect of Li on the tensile properties of cast Al-Mg2Si metal matrix composite
, Article Materials Science and Engineering A ; Volume 490, Issue 1-2 , 2008 , Pages 250-257 ; 09215093 (ISSN) ; Emamy, M ; Varahram, N ; Nemati, N ; Sharif University of Technology
2008
Abstract
The effects of both Li modification and cooling rate on the microstructure and tensile properties of an in situ prepared Al-15%Mg2Si composite were investigated. It was found that the addition of 0.3%Li reduces the average size of Mg2Si primary particles from ∼30 to ∼6 μm. The effect of cooling rate was investigated by the use of a mold with different section test bars. The results showed an increase in both UTS and elongation values with reduction in section thicknesses corresponding to increasing cooling rates. Adding Li also raised the tensile strength and elongation values and reduced the number of decohered particles observed in fracture surfaces thereby increasing the alloy's...
Visible Light Saturable Absorber Near-Field Nanolithography
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Ali Reaz (Supervisor)Fabrication of Metallic Nano-Tip Field Emitters and Measurement
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor)
Abstract
The need for integration of electron guns together with thermal considerations of thermionic cathodes has led to design new cold cathode guns based on field emission phenomenon. In first part of this thesis, basic field emission theories, fabrication methods of field emitter arrays, effect of different parameters on the field emission properties of field emitter arrays and applications of these arrays are investigated. After setting up fabrication methods of nano-tip field emitters, in the second part of thesis, Si nano-tips and Si field emitter arrays are fabricated using of thermal oxidation of silicon substrate, lithography, and chemical etching of silicon oxide and silicon substrate. Si...
Particle Focusing on a Lab on a Disk System
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor)
Abstract
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...
Design and Fabrication of Microfluidic System as Concentration Gradient Generator
, M.Sc. Thesis Sharif University of Technology ; Saadatmand, Maryam (Supervisor)
Abstract
According to today’s medicine progress, the need for improving the medical facilities have been increased. Within the human body, the biomolecules concentration gradient is regulating the cell functions. Biological processes such as immune response, wound healing, and cancer metastasis have been affected by the bimolecular concentration gradient. So understanding the cell behavior in the presence of a chemical gradient can improve the understanding from these biological processes, and also would help in medical researches. On the other hand, finding the appropriate dose of the drugs and in some cases finding the most effective drug is a clinical challenge that made a new field of research in...
Analysis of the Interaction of Electron Beam and External Field by Considering Space Charge Effect and its Application in EBL Nanolithography
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bizhan (Supervisor) ; Mehrani, Khashayar (Co-Advisor)
Abstract
Due to tremendous growth in usage of electron beams in different applications like VLSI, welding, chemical processes, Polymer industry and medical applications, precise study of these beams is of great importance. One of the most important parameters in studying electron beams characteristics is the phenomenon and effect of space charge. Although in most methods of analyzing electron optical systems, this effect is neglected, however in high density beams, this effect is bold. Space charge effect is due to interaction and electrostatic repulsion force between each of the electrons in the beam, which results in a change in shape and also divergence of beam. It is worth to mention that in...
Fabrication and Characterization of Patterned Carbon Nanotubes Network on the Silicon Wafer, by Plasma Enhanced Chemical Vapor Deposition
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor)
Abstract
Carbon nanotubes, due to their extraordinary electronic and physical properties, have attracted much attention in the last decade. Some of their potential applications are in CNT-field effect transistor, field emission devices, physical and chemical sensors, micro and Nanoelectromechanical systems and Nano antenna. In this thesis, we have first reviewed some features of carbon nanotubes and the advantages of PECVD method compared with thermal CVD. In the second part the role of some of the materials (such as H2/NH3/C2H4) in CNT growth are studied. We created a square pattern on the silicon wafer by photolithography. Afterwards, titanium and nickel deposition is done on the mentioned pattern....
Design and Fabrication of Tip for a Nanolithography System
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor)
Abstract
Various applications of nanostructures in electronics, optoelectronics, MEMS, photonics and plasmonic make their fabrication an interesting research topic recently. Progress in nanotechnology depends on the capability to fabricate, position and interconnect nanometer-scale structures. The development of fabrication devices with nanoscales is mainly dependent on the existence of a suitable nanolithography approach. Patterning materials with nanoscale features aimed at improving integration and device performance faced several challenges. The limitation of conventional lithography systems including resolution related issues, operational costs and lack of flexibility to pattern organic and...
Theoretical model for visible light saturable absorber nanolithography
, Article Journal of Optics (United Kingdom) ; Volume 14, Issue 12 , 2012 ; 20408978 (ISSN) ; Bahrampour, A. R ; Sharif University of Technology
2012
Abstract
In this paper a saturable absorber medium is employed as an optical limiter to reduce the spot size to the range of several tens of nanometres. The characteristics of a Gaussian beam are theoretically analysed upon propagation through the saturable absorber medium. Based on Maxwell equations a system of coupled nonlinear ordinary differential equations for intensity, beam radius and beam curvature is obtained. Theoretical analyses and numerical results show that the behaviour of a Gaussian beam in a saturable absorber medium strongly depends on the initial characteristics of the laser beam. Numerical results indicate that, depending on the initial conditions and a suitable saturable absorber...
Oxidation effects on transport characteristics of nanoscale MOS capacitors with an embedded layer of silicon nanocrystals obtained by low energy ion implantation
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 124-125, Issue SUPPL , 2005 , Pages 494-498 ; 09215107 (ISSN) ; Shalchian, M ; Benassayag, G ; Coffin, H ; Bonafos, C ; Schamm, S ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we have studied the effect of annealing under slightly oxidizing ambient (N2 + O2) on the structural and electrical characteristics of a limited number of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultra-low energy (1 keV) ion implantation and annealing. Material characterization techniques including transmission electron microscopy (TEM), Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on less than one hundred nanoparticles by...
Investigating Electrochemical Behavior of Biosensor Based on Vertically Aligned Carbon Nanotubes
, Ph.D. Dissertation Sharif University of Technology ; Shahrokhian, Saeed (Supervisor) ; Iraji Zad, Azam (Co-Advisor) ; Mohajerzadeh, Shamsoddin (Co-Advisor) ; Vossoughi, Manoochehr (Co-Advisor)
Abstract
In this research we focus on fabrication, characterization and performance of biosensors based on vertically aligned carbon nanotubes. Carbon nanotubes have been used as high density carbon nanotubes and nanoelectrode array. Carbon nanotubes have been grown using plasma enhanced chemical vapor deposition method. Characterization and performance of biosensors have been studied by cyclic voltammetry and electrochemical impedance spectroscopy methods.
The mediator-less glutamate biosensor is prepared based on covalently attached glutamate dehydrogenase on vertically aligned carbon nanotubes. The biosensor has a low detection limit of 57 nM, two linear range of 0.1-20 µM with sensitivity of...
The mediator-less glutamate biosensor is prepared based on covalently attached glutamate dehydrogenase on vertically aligned carbon nanotubes. The biosensor has a low detection limit of 57 nM, two linear range of 0.1-20 µM with sensitivity of...
Recent advancements in bulk metallic glasses and their applications: A review
, Article Critical Reviews in Solid State and Materials Sciences ; Volume 43, Issue 3 , 2018 , Pages 233-268 ; 10408436 (ISSN) ; Nemati, A ; Rahman, Z.U ; Shah, U. H ; Asgar, H ; Haider, W ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Bulk metallic glasses (BMGs), that display extraordinary properties of high strength, corrosion resistance, polymer-like formability, and excellent magnetic properties, are emerging as modern quintessential engineering materials. BMGs have garnered significant research enthusiasm owing to their tremendous technological and scientific standing. In this article, the recent advancements in the field of BMGs and their applications are put in a nutshell. Novel state-of-the-art production routes and nano/microimprinting strategies with salient features capable of circumventing the processing related complexities as well as accelerating modern developments, are briefly summarized. Heterogeneous BMG...
Control of chaos in atomic force microscopes using delayed feedback based on entropy minimization
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 14, Issue 3 , 2009 , Pages 637-644 ; 10075704 (ISSN) ; Alasty, A ; Sharif University of Technology
2009
Abstract
Active chaos control of a tapping mode atomic force microscope (AFM) model via delayed feedback method is presented. The feedback gain is obtained and adapted according to a minimum entropy (ME) algorithm. In this method, stabilizing an unstable fixed point of the system Poincare map is achieved by minimizing the entropy of points distribution on the Poincare section. Simulation results show the feasibility of the proposed method in applying the delayed feedback technique for chaos control of an AFM system. © 2007 Elsevier B.V. All rights reserved
Storage of Ag nanoparticles in pore-arrays of SU-8 matrix for antibacterial applications
, Article Journal of Physics D: Applied Physics ; Volume 42, Issue 13 , 2009 ; 00223727 (ISSN) ; Abdolahad, M ; Asadi, R ; Sharif University of Technology
2009
Abstract
Silver nanoparticles (NPs) stored in pore-arrays (pa) SU-8 photoresist layer were utilized as an antibacterial nanocomposition against E. coli bacteria. The pa-SU-8 matrix was fabricated by an optical interference lithography method resulting in small pores with a diameter of ∼50 nm and a depth of ∼100 nm. The Ag NPs were deposited on the soft polymeric matrix at different drying temperatures of 50 and 90 °C. X-ray photoelectron spectroscopy showed that the deposited silver NPs were substantially in the metallic state, independent from the drying condition. However, the concentration of the immobilized Ag NPs on the film surface increased (by a factor of 2.5) at the higher drying...
Design and fabrication of a novel microfluidic system for enrichment of circulating tumor cells with the assistance of computer simulations
, Article Avicenna Journal of Medical Biotechnology ; Volume 11, Issue 4 , 2019 , Pages 277-284 ; 20082835 (ISSN) ; Vossoughi, M ; Alemzadeh, I ; Sharif University of Technology
Avicenna Research Institute
2019
Abstract
Background: Cancer is the first cause of death in developed countries. The heterogeneous nature of cancer requires patient-specified treatment plans. One reliable approach is collecting Circulating Tumour Cells (CTCs) and using them for prognosis and drug response assessment purposes. CTCs are rare and their separation from normal cell requires high-accuracy methods. Methods: A microfluidic cell capture device to separate CTCs from peripheral blood is presented in this study. The CTC separation device applies hydrodynamic forces to categorize cells according to their sizes. The proposed device is designed and evaluated by numerical simulations and validated experimentally. The simulation...
Shedding light on pseudocapacitive active edges of single-layer graphene nanoribbons as high-capacitance supercapacitors
, Article ACS Applied Energy Materials ; Volume 2, Issue 5 , 2019 , Pages 3665-3675 ; 25740962 (ISSN) ; Esfandiar, A ; Mehdipour, H ; Chaigneau, M ; Irajizad, A ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2019
Abstract
In the field of energy storage by high-rate supercapacitors, there has been an upper limit for the total interfacial capacitance of carbon-based materials. This upper limit originates from both quantum and electric double-layer capacitances. Surpassing this limit has been the focus of intense research in this field. Here, we precisely investigate the effect of chemical functional groups and physical confinement on the electrochemical performance of graphene nanoribbons. We present the results of a quasi-one-dimensional single-layer graphene nanoribbon (120 nm in width and -100 μm in length) microelectrode fabricated by mechanical exfoliation of graphite, followed by electron beam lithography...