شبيه سازي ديناميك مولكولي پديده الكتروكينتيك در جريان هاي الكترواسموتيك و الكتروفورتيك در نانو كانال ها

چكيده انگليسي :

Molecular Dynamics Simulation of Electrokinetic Phenomena in Electroosmotic and Electrophoretic Flows in Nanochannels Majid Rezaei Majid Rezaei@me iut ac ir Date of Submission 8 1 2013 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor A R Azimian Azimian@cc iut ac irAbstractFluid transport is one of the most challenging problems in the nanotechnology To transfer fluid in a nano channel avariety of nano fluidic systems consisting of valves pumps and mixers have been used But some parts such asnano valves and nano pumps with moving components are complicated to design and fabricate and they are proneto mechanical failure due to fatigue and fabrication defects In addition there are many restrictions for flow controlin these devices Therefore alternative means are needed for fluid transport in nano scale One of themost importantand best known ways to transport fluid in this scale is to use the electrokinetic phenomena In this technique there isno need to any moving part and fluid flow is due to the effect of an applied electric field Two phenomena based onthe electrokinetic i e electroosmotic and electrophoretic flow are studied Generation of an electric double layer EDL which is the result of the interaction between an ionized solution and a static charge on a dielectric surface isthe source of flow in both electroosmotic and electrophoretic flows We study these flows using a moleculardynamic simulation MDS model Molecular dynamics is a computer simulation of physicalmovements of atoms and molecules The atoms and molecules are allowed to interact for a period of time giving aview of the motion of the atoms In the most common version the trajectories of atoms and molecules aredetermined by numerically solving the Newton s equations of motion for a system of interacting particles where forces between the particles and potential energy are defined by molecular mechanics force fields In thepresent study the effect of various factors affecting the direction and intensity of these flows in a slab nanochannel isbeing studied To achieve this goal the effect of electrolyte solution ion concentration surface charge density applied electric field simulation temperature channel height surface density and surface roughness on theelectroosmotic fluid transport is studied In order to study the electrophoretic flow some highly charged macroionsare added to the system The effect of various parameters such as macroion s charge macroion s diameter appliedelectric field and simulation temperature on the electrophoretic flow is investigated In the present study macroionsare simulated by means of two models hard model and soft model It is attempted to study the effect of variousparameters on the velocity profiles and flow concentrations and try to interpret these results using the properties ofthe electric double layer In addition the combined flow created by adding macroions to the electroosmotic flow isstudied too It was found that the combined flow is stronger than both electroosmotic and electrophoretic flowsalone Also various phenomenons such as charge inversion flow reversal and multi layering of the stern sub layerwere observed during these studies Keywords Electrokinetic phenomena Electroosmotic Electrophoretic Electric Double Layer Molecular Dynamics

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شبيه سازي ديناميك مولكولي پديده الكتروكينتيك در جريان هاي الكترواسموتيك و الكتروفورتيك در نانو كانال ها

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