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    Electrowetting-induced droplet jumping over topographically structured surfaces

    , Article Materials Research Express ; Volume 6, Issue 8 , 2019 ; 20531591 (ISSN) Merdasi, A ; Moosavi, A ; Shafii, M. B ; Sharif University of Technology
    Institute of Physics Publishing  2019
    We analyze the process of electrowetting-induced jumping of droplets away from a substrate with a geometric heterogeneity in the form of a cone and compare the results with those of a flat substrate in different wettabilities and hydrophobicities. Our results reveal that the droplet dynamics can be enhanced through applying a topographic heterogeneity. However, increasing the height of the cones does not always provide a better condition for the jumping and there is an optimum value for the height of the cones. The enhancement is due to the fact that more liquid flowing affects the pressure gradient within the droplet leading to a higher jumping velocity. It is shown that for the flat... 

    Effects of Biocompatible Substrates on Electrical Properties of Graphene

    , M.Sc. Thesis Sharif University of Technology Simchi, Mohammad (Author) ; Fardmanesh, Mehdi (Supervisor)
    Graphene is a single-atomic two-dimensional crystal that has considerable properties due to its unique structure and physics with applications in different fields. Due to its atomic thin thickness, substrates have a considerable effect on the electrical properties of Graphene. As these effects are determinative of the general behavior of systems, one should consider this effect in the design and fabrication of a device. Moreover, the conventional fabrication methods for Graphene-based electronic devices restrict the possibility of the device fabrication on a wide range of substrates, specially flexible and biocompatible substrates.In this work, the LPCVD Graphene growth process has been... 

    Role of graphene surface ripples and thermal vibrations in molecular dynamics of C60

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 32 , 2019 , Pages 20026-20036 ; 19327447 (ISSN) Mofidi, S. M ; Nejat Pishkenari, H ; Ejtehadi, M. R ; Akimov, A. V ; Sharif University of Technology
    American Chemical Society  2019
    Nanocars are artificial molecular machines with chassis, axles, and wheels designed for nanoscale transport at materials' surfaces. Understanding the dependence of surface dynamics of nanocars on the substrate's physicochemical properties is critical to the design of the transport properties of such man-made nanoscale devices. Among the multitude of potential substrates for the nanotransporters, graphene exhibits intrinsic ripples on its surface, which may affect the surface dynamics of nanocars. In this work, we report our molecular dynamics study of motion of C60, a popular nanocar wheel, on the graphitic substrates with systematically controllable surface ripples. We find that surface... 

    Molecular dynamics simulation of manipulation of metallic nanoclusters on double-layer substrates [electronic resource]

    , Article Physica E: Low-dimensional Systems and Nanostructures ; 2010, Vol. 42, No. 9, pp. 2364-2374 Mahboobi, H. (Hanif) ; Meghdari, Ali ; Jalili, Nader ; Amiri, Farshid ; Sharif University of Technology
    Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on double-layer surfaces. The system parts are made of transition metals. The conditions which are subjected to change in the tests are material combinations for cluster, main substrate and lubricant layer (adlayer). In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Obtaining this sort of knowledge is highly beneficial for further experiments in order to be able to plan the conditions and routines, which guarantee better success in the manipulation process  

    Controlling the diffusive motion of fullerene-wheeled nanocars utilizing a hybrid substrate

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 42 , 2019 , Pages 26018-26030 ; 19327447 (ISSN) Nemati, A ; Nejat Pishkenari, H ; Meghdari, A ; Ge, S. S ; Sharif University of Technology
    American Chemical Society  2019
    In the previous years, a few types of nanocars have been built with the promising potential to transport other molecules, to provide bottom-up assembly, or to perform other mechanical tasks. In this study, we propose a method to convert the diffusive displacement of nanocars to a guided motion in a desired path by adding some impurity atoms in the substrate. We investigated the motion of C60 as well as the nanotruck and the nanocar on a flat gold substrate containing silver contamination and conversely a silver substrate containing gold contamination at the different temperatures. The results showed that silver impurity on the gold substrate act as a repellent obstacle in the path of C60... 

    The effect of material property grading on the rolling contact stress field

    , Article Mechanics Research Communications ; Vol. 55, issue , 2014 , p. 45-52 Alinia, Y ; Guler, M. A ; Adibnazari, S ; Sharif University of Technology
    This paper investigates the subsurface stress field induced by a rigid cylinder rolling over a functionally graded coating-substrate system. The Fourier transform is employed to extract the stress components within the graded coating and the homogeneous substrate. The distributions of the stresses are given through the depth and along the coating-substrate interface. The contour plots of normalized Von Mises stresses are provided as well. The results indicate that continuous variation of the shear modulus substantially reduces the difference between the in-plane stresses along the interface. Also, the softening coating leads to the minimum value of the stress concentration near the contact... 

    Simple One-Step Fabrication of Semiconductive Lateral Heterostructures Using Bipolar Electrodeposition

    , Article Physica Status Solidi - Rapid Research Letters ; 2018 ; 18626254 (ISSN) Jamilpanah, L ; Azizmohseni, S ; Hosseini, S. A ; Hasheminejad, M ; Vesali, N ; Iraji Zad, A ; Pourfath, M ; Mohseni, S. M ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    Unidirectional current flow is at the heart of modern electronics, which has been conceived by making p–n junctions or Schottky barriers between different kinds of materials. Within such elements, however, synthesis of thin film lateral heterostructures has so far remained challenging. Here, a one-step simple synthesis of p-type, n-type, and metallic lateral heterostructures using bipolar electrodeposition (BPE) technique is reported. Molybdenum oxides and sulfides with gradient of oxygen and sulfur are deposited at a metallic substrate. A lateral heterostructure is achieved with electrical properties that change from p- to n-type semiconductor and then to metal by moving in the plane of the... 

    Propagation and refraction of left-handed plasmons on a semiconducting substrate covered by graphene

    , Article Optics Letters ; Volume 43, Issue 9 , 2018 , Pages 2010-2013 ; 01469592 (ISSN) Zivari, A. P ; Bagheri, A. M ; Rejaei, B ; Khavasi, A ; Sharif University of Technology
    OSA - The Optical Society  2018
    We show that a plasmonic semiconductor substrate can support highly confined surface plasmons when it is covered by a graphene layer. This occurs when the imaginary part of graphene conductivity and real part of the effective permittivity of the surrounding medium become simultaneously negative. Full-wave electromagnetic simulations demonstrate the occurrence of negative refraction and two-dimensional lensing at the interface separating regions supporting conventional right-handed graphene plasmons and left-handed surface plasmon polaritons. © 2018 Optical Society of America  

    A new approach for preparation of semi-transparent superhydrophobic coatings by ultrasonic spray hydrolysis of methyltrimethoxysilane

    , Article Progress in Organic Coatings ; Volume 135 , 2019 , Pages 248-254 ; 03009440 (ISSN) Rahemi Ardekani, S ; Sabour Rouh Aghdam, A ; Nazari, M ; Bayat, A ; Saievar Iranizad, E ; Sharif University of Technology
    Elsevier B.V  2019
    A novel nebulizing spray hydrolysis approach was used for preparation of semi-transparent superhydrophobic coatings. Methyltrimethoxysilane was dissolved in water:ethanol mixture and ultrasonically sprayed on different substrates. Superhydrophobic coatings with a contact angle (CA) as high as 164° and a sliding angle below 5° were obtained. FESEM and AFM revealed a hierarchical micro-nano binary structure with nanometric roughness of the coatings. The coated glass substrate exhibited transmittance close to 80%. The prepared coating showed great self-cleaning and water jet repellency behaviors. The superhydrophobicity of the samples was remained after subjecting to ambient conditions for 50... 

    Coarsening Dynamics of Nanodroplets

    , M.Sc. Thesis Sharif University of Technology Asgari, Mahdi (Author) ; Moosavi, Ali (Supervisor)
    Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate.... 

    Molecular dynamics simulation of manipulation of metallic nanoclusters on double-layer substrates

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 42, Issue 9 , 2010 , Pages 2364-2374 ; 13869477 (ISSN) Mahboobi, S. H ; Meghdari, A ; Jalili, N ; Amiri, F ; Sharif University of Technology
    Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on double-layer surfaces. The system parts are made of transition metals. The conditions which are subjected to change in the tests are material combinations for cluster, main substrate and lubricant layer (adlayer). In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Obtaining this sort of knowledge is highly beneficial for further experiments in order to be able to plan the conditions and routines, which guarantee better success in the manipulation process  

    Mechanism of 1,12-Dicarba-closo-dodecaborane Mobility on Gold Substrate as a Nanocar Wheel

    , Article Journal of Physical Chemistry C ; Volume 120, Issue 26 , 2016 , Pages 14048-14058 ; 19327447 (ISSN) Hosseini Lavasani, S.M ; Nejat Pishkenari, H ; Meghdari, A ; Sharif University of Technology
    American Chemical Society  2016
    We studied the mobility of p-carborane on a gold surface by analyzing the potential energy surfaces (PES) and simulating the motion of p-carborane using the classical molecular dynamics (MD) method. In the first section, we calculated the PES of p-carborane molecules on a gold surface during pure translation (sliding) and pure rotation independently and then employed this PES to predict the probable motion of p-carborane. These calculations were performed in several major orientations during sliding as well as different fixed positions during rotational movements to enable us to find the p-carborane motion threshold on a gold surface. In the second section, we use classical MD in isothermal... 

    Dynamics of nanodroplets on topographically structured substrates

    , Article Journal of Physics Condensed Matter ; Volume 21, Issue 46 , 2009 ; 09538984 (ISSN) Moosavi, A ; Rauscher, M ; Dietrich, S ; Sharif University of Technology
    Mesoscopic hydrodynamic equations are solved to investigate the dynamics of nanodroplets positioned near a topographic step of the supporting substrate. Our results show that the dynamics depends on the characteristic length scales of the system given by the height of the step and the size of the nanodroplets as well as on the constituting substances of both the nanodroplets and the substrate. The lateral motion of nanodroplets far from the step can be described well in terms of a power law of the distance from the step. In general the direction of motion depends on the details of the effective laterally varying intermolecular forces. But for nanodroplets positioned far from the step it is... 

    Ring microgyroscope modeling and performance evaluation

    , Article JVC/Journal of Vibration and Control ; Volume 12, Issue 5 , 2006 , Pages 537-553 ; 10775463 (ISSN) Esmaeili, M ; Durali, M ; Jalili, N ; Sharif University of Technology
    This paper discusses the effects of substrate motions on the performance of microgyroscopes modeled as ring structures. Using the Extended Hamiltonian Principle, the equations of motion of a ring micro-gyroscope are derived, and the natural frequency equation and response characteristics are extracted in closed form for the case where the substrate undergoes normal rotation. The Galerkin approximation is then used to arrive at the ordinary differential equations of motion for the ring. In these equations, the effects of angular, centripetal and Coriolis accelerations are all apparent. The response of the system to different inputs is studied and the system sensitivity to variation in input... 

    Analysis, Design, and Fabrication of Coplanar Waveguide to Substrate Integrated Waveguide

    , M.Sc. Thesis Sharif University of Technology Ahmadian, Arman (Author) ; Rejaei Salmasi, Behzad (Supervisor) ; Sarvari, Reza (Supervisor)
    An important issue in High-Frequency circuits is the transmission of electrical signals in Integrated Circuits and Printed Circuit Boards (PCBs). At high frequencies, however, the often used transmission lines suffer from high conductor and substrate loss as well as unwanted electromagnetic coupling to other circuit elements caused by parasitic substrate surface. One method through which both of the above problems may be solved is utilizing waveguide structures on PCBs and ICs. In this way, due to the reduction of conductor loss, a large proportion of signal passes easily. Moreover, and because of closed nature of cavity waveguides, neighboring circuits are protected against electromagnetic... 

    Fabrication of Silicon Nanowires with various Silicon Substrates and Investigation of the structural Properties and their Behavior

    , M.Sc. Thesis Sharif University of Technology Teymouri, Arastoo (Author) ; Askari, Masoud (Supervisor)
    In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy... 

    Dynamic modeling and sensitivity analysis of atomic force microscope pushing force in nanoparticle manipulation on a rough substrate [electronic resource]

    , Article Journal of Advanced Science, Engineering and Medicine ; 2013, Vol. 5, pp. 1-10 Babahosseini, H. (Hesam) ; Mahboobi, Seyed Hanif ; Meghdari, Ali ; Sharif University of Technology
    An Atomic Force Microscope (AFM) is a capable tool to manipulate nanoparticles by exerting pushing force on the nanoparticles located on the substrate. In reality, the substrate cannot be considered as a smooth surface particularly at the nanoscale. Hence, the particle may encounter a step on the substrate during a manipulation. In this study, dynamics of the nanoparticle on a stepped substrate and critical pushing force in the manipulation are investigated. There are two possible dynamic modes that may happen in the manipulation on the stepped substrate. In one mode, the nanoparticle may slide on the step edge and then climb up to the step which is a desired mode. Another possible mode is... 

    Planar molecular dynamics simulation of Au clusters in pushing process

    , Article International Journal of Nanomanufacturing ; Vol.5, No.3/4 , 2010 , pp.288-296 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology
    Based on the fact that the manipulation of fine nanoclusters calls for more precise modelling, the aim of this paper is to conduct an atomistic investigation for interaction analysis of particle-substrate system for pushing and positioning purposes. In the present research, 2D molecular dynamics simulations have been used to investigate such behaviours. Performing the planar simulations can provide a fairly acceptable qualitative tool for our purpose while the computation time is reduced extremely in comparison to 3D simulations. To perform this study, Nose-Hoover dynamics and Sutton-Chen interatomic potential will be used to investigate the behaviour of the aforementioned system. Pushing of... 

    Morphology of nanodroplets on structured surfaces

    , Article Journal of Physics D: Applied Physics ; Volume 46, Issue 21 , May , 2013 ; 00223727 (ISSN) Vahid, A ; Moosavi, A ; Sharif University of Technology
    We report different morphologies of nanodroplets over various topographical features of the supporting substrates. The effects of different parameters such as the profile of the disjoining pressure, droplet size and the geometrical parameters are studied and discussed. Also, the effects of a coating layer on the surface of the substrate are determined. It is demonstrated that the nanodroplets at some positions are not stable and gradually move to more stable positions so that the system has less energy. For grooves this results in a series of morphology diagrams of the nanodroplets over the grooves as a function of the grooves' width and the liquid volume  

    Fabrication of gas ionization sensor using carbon nanotube arrays grown on porous silicon substrate

    , Article Sensors and Actuators, A: Physical ; Volume 162, Issue 1 , 2010 , Pages 24-28 ; 09244247 (ISSN) Nikfarjam, A ; Iraji Zad, A ; Razi, F ; Mortazavi, S. Z ; Sharif University of Technology
    We fabricated gas sensors based on field ionization from multiwalled carbon nanotube (MWCNT) arrays grown on porous silicon templates. MWCNTs were grown through thermal chemical vapor deposition. We measured breakdown voltages, discharge and pre-discharge currents of the device for various gases in different concentrations. Our gas ionization sensors (GIS) presented good sensitivity, selectivity and short response time. The GISs based on porous substrates showed higher discharge current and good mechanical stability in comparison to those which were fabricated on polished silicon substrates. Additionally, we applied a high electric field to align CNTs. This increased the pre-breakdown...