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Chun Yang - One of the best experts on this subject based on the ideXlab platform.
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Advances in Electrokinetics and their applications in micro/nano fluidics
Microfluidics and Nanofluidics, 2012Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic Phenomena originally developed in colloid chemistry have drawn great attention in micro- and nano-fluidic lab-on-a-chip systems for manipulation of both liquids and particles. Here we present an overview of advances in Electrokinetic Phenomena during recent decades and their various applications in micro- and nano-fluidics. The advances in Electrokinetics are generally classified into two categories, namely Electrokinetics over insulating surfaces and Electrokinetics over conducting surfaces. In each category, the Phenomena are further grouped according to different physical mechanisms. For each category of Electrokinetics, the review begins with basic theories, and followed by their applications in micro- and/or nano-fluidics with highlighted disadvantages and advantages. Finally, the review is ended with suggested directions for the future research.
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advances in Electrokinetics and their applications in micro nano fluidics
Microfluidics and Nanofluidics, 2012Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic Phenomena originally developed in colloid chemistry have drawn great attention in micro- and nano-fluidic lab-on-a-chip systems for manipulation of both liquids and particles. Here we present an overview of advances in Electrokinetic Phenomena during recent decades and their various applications in micro- and nano-fluidics. The advances in Electrokinetics are generally classified into two categories, namely Electrokinetics over insulating surfaces and Electrokinetics over conducting surfaces. In each category, the Phenomena are further grouped according to different physical mechanisms. For each category of Electrokinetics, the review begins with basic theories, and followed by their applications in micro- and/or nano-fluidics with highlighted disadvantages and advantages. Finally, the review is ended with suggested directions for the future research.
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ac Electrokinetic Phenomena over semiconductive surfaces: effective electric boundary conditions and their applications.
Physical review. E Statistical nonlinear and soft matter physics, 2011Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic boundary conditions are derived for ac Electrokinetic Phenomena over leaky dielectric (i.e., semiconducting) surfaces. Such boundary conditions correlate the electric potentials across a semiconductor-electrolyte interface (consisting of an electric double layer inside the electrolyte solution and a space charge layer inside the semiconductor) in an ac electric field with arbitrary wave forms. The presented Electrokinetic boundary conditions allow for evaluation of the induced ζ potential contributed by both bond charges (due to electric polarization) and free charges (due to electric conduction) from the leaky dielectric materials. Two well-known limiting cases, (i) the conventional insulating boundary condition and (ii) the perfectly polarizable boundary condition, can be recovered from the generalized Electrokinetic boundary conditions derived in the present paper. Subsequently, we demonstrate the implementation of the derived boundary conditions for analyzing the ac induced-charge Electrokinetic flow around a semiconducting cylinder. The results show that the flow circulations exist around the semiconducting cylinder and become stronger in the ac field with a lower frequency and around the semiconducting cylinder with a higher conductivity.
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ac Electrokinetic Phenomena over semiconductive surfaces: effective electric boundary conditions and their applications.
Physical Review E, 2011Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic boundary conditions are derived for ac Electrokinetic Phenomena over leaky dielectric (i.e., semiconducting) surfaces. Such boundary conditions correlate the electric potentials across a semiconductor-electrolyte interface (consisting of an electric double layer inside the electrolyte solution and a space charge layer inside the semiconductor) in an ac electric field with arbitrary wave forms. The presented Electrokinetic boundary conditions allow for evaluation of the induced $\ensuremath{\zeta}$ potential contributed by both bond charges (due to electric polarization) and free charges (due to electric conduction) from the leaky dielectric materials. Two well-known limiting cases, (i) the conventional insulating boundary condition and (ii) the perfectly polarizable boundary condition, can be recovered from the generalized Electrokinetic boundary conditions derived in the present paper. Subsequently, we demonstrate the implementation of the derived boundary conditions for analyzing the ac induced-charge Electrokinetic flow around a semiconducting cylinder. The results show that the flow circulations exist around the semiconducting cylinder and become stronger in the ac field with a lower frequency and around the semiconducting cylinder with a higher conductivity.
Cunlu Zhao - One of the best experts on this subject based on the ideXlab platform.
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Advances in Electrokinetics and their applications in micro/nano fluidics
Microfluidics and Nanofluidics, 2012Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic Phenomena originally developed in colloid chemistry have drawn great attention in micro- and nano-fluidic lab-on-a-chip systems for manipulation of both liquids and particles. Here we present an overview of advances in Electrokinetic Phenomena during recent decades and their various applications in micro- and nano-fluidics. The advances in Electrokinetics are generally classified into two categories, namely Electrokinetics over insulating surfaces and Electrokinetics over conducting surfaces. In each category, the Phenomena are further grouped according to different physical mechanisms. For each category of Electrokinetics, the review begins with basic theories, and followed by their applications in micro- and/or nano-fluidics with highlighted disadvantages and advantages. Finally, the review is ended with suggested directions for the future research.
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advances in Electrokinetics and their applications in micro nano fluidics
Microfluidics and Nanofluidics, 2012Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic Phenomena originally developed in colloid chemistry have drawn great attention in micro- and nano-fluidic lab-on-a-chip systems for manipulation of both liquids and particles. Here we present an overview of advances in Electrokinetic Phenomena during recent decades and their various applications in micro- and nano-fluidics. The advances in Electrokinetics are generally classified into two categories, namely Electrokinetics over insulating surfaces and Electrokinetics over conducting surfaces. In each category, the Phenomena are further grouped according to different physical mechanisms. For each category of Electrokinetics, the review begins with basic theories, and followed by their applications in micro- and/or nano-fluidics with highlighted disadvantages and advantages. Finally, the review is ended with suggested directions for the future research.
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ac Electrokinetic Phenomena over semiconductive surfaces: effective electric boundary conditions and their applications.
Physical review. E Statistical nonlinear and soft matter physics, 2011Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic boundary conditions are derived for ac Electrokinetic Phenomena over leaky dielectric (i.e., semiconducting) surfaces. Such boundary conditions correlate the electric potentials across a semiconductor-electrolyte interface (consisting of an electric double layer inside the electrolyte solution and a space charge layer inside the semiconductor) in an ac electric field with arbitrary wave forms. The presented Electrokinetic boundary conditions allow for evaluation of the induced ζ potential contributed by both bond charges (due to electric polarization) and free charges (due to electric conduction) from the leaky dielectric materials. Two well-known limiting cases, (i) the conventional insulating boundary condition and (ii) the perfectly polarizable boundary condition, can be recovered from the generalized Electrokinetic boundary conditions derived in the present paper. Subsequently, we demonstrate the implementation of the derived boundary conditions for analyzing the ac induced-charge Electrokinetic flow around a semiconducting cylinder. The results show that the flow circulations exist around the semiconducting cylinder and become stronger in the ac field with a lower frequency and around the semiconducting cylinder with a higher conductivity.
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ac Electrokinetic Phenomena over semiconductive surfaces: effective electric boundary conditions and their applications.
Physical Review E, 2011Co-Authors: Cunlu Zhao, Chun YangAbstract:Electrokinetic boundary conditions are derived for ac Electrokinetic Phenomena over leaky dielectric (i.e., semiconducting) surfaces. Such boundary conditions correlate the electric potentials across a semiconductor-electrolyte interface (consisting of an electric double layer inside the electrolyte solution and a space charge layer inside the semiconductor) in an ac electric field with arbitrary wave forms. The presented Electrokinetic boundary conditions allow for evaluation of the induced $\ensuremath{\zeta}$ potential contributed by both bond charges (due to electric polarization) and free charges (due to electric conduction) from the leaky dielectric materials. Two well-known limiting cases, (i) the conventional insulating boundary condition and (ii) the perfectly polarizable boundary condition, can be recovered from the generalized Electrokinetic boundary conditions derived in the present paper. Subsequently, we demonstrate the implementation of the derived boundary conditions for analyzing the ac induced-charge Electrokinetic flow around a semiconducting cylinder. The results show that the flow circulations exist around the semiconducting cylinder and become stronger in the ac field with a lower frequency and around the semiconducting cylinder with a higher conductivity.
Nataliya A Mishchuk - One of the best experts on this subject based on the ideXlab platform.
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Influence of Electrokinetic Phenomena on the Mass Transfer of Electrofiltration Disinfection of Water
Research Bulletin of the National Technical University of Ukraine "Kyiv Politechnic Institute", 2017Co-Authors: Larysa L. Lysenko, Nataliya A MishchukAbstract:В ackground. The development of a method for increasing the efficiency of an installation for electrochemical water disinfection. Оbjective. The aim of the paper is the study of the influence of Electrokinetic Phenomena on the mass transfer in a system with a charged porous diaphragm, aimed at determining the conditions that allow increasing the efficiency of the process of electrofiltration water disinfection while maintaining the parameters of its conduct and ensuring the necessary degree of decontamination. Methods. The determination of the efficiency of the microporous filter element in various ways of organizing the electrofiltration process is conducted. Results. The efficiency of the microporous charged element depends on the location of the cathode and the anode, which determines the direction of the electroosmosis with respect to the flow of the treated water. Increasing the strength of the electric field while maintaining the value of the operating pressure leads to an intensification of the processes affecting the efficiency. Conclusions. The location of electrodes, which ensures the counter motion of the hydrodynamic flow of the treated water and the electroosmotic flow occurring in the pores of the charged diaphragm, allows substantially increasing the productivity of the disinfection process.
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concentration polarization of interface and non linear Electrokinetic Phenomena
Advances in Colloid and Interface Science, 2010Co-Authors: Nataliya A MishchukAbstract:Abstract The review addresses the peculiarities of concentration polarization caused by an electric current passing through conducting and around nonconducting charged materials. The conditions of emergence of an induced space charge of large density and thickness behind an electrical double layer, leading to strong non-linearity of electroosmosis and electrophoresis, are analyzed. Basic findings about concentration polarization, its theoretical modeling and experimental investigations, as well as its influence on Electrokinetic Phenomena and mass transfer through ion-exchange materials are discussed from the point of view of the fundamental knowledge about polarization processes and from the perspective of their practical application. The analysis focuses on the main properties of concentration polarization, electroosmotic flow of liquid around single fixed particles and through the system of particles, and electrophoresis of particles suspended in aqueous medium and current through flat, spherical and cylindrical interfaces and membranes with heterogeneous conductivity. The paper also presents the general ideas of concentration polarization and non-linear Electrokinetic Phenomena in case of nonconducting particles and their dependence on particle surface electroconductivity. Existing theoretical models describing polarization of nonconducting particles at high and low Peclet numbers are analyzed, with appropriate experimental data being provided to validate the theory. A joint analysis of polarization of conducting and nonconducting particles completes the review.
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The role of water dissociation in concentration polarisation of disperse particles
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Nataliya A MishchukAbstract:Abstract The peculiarities of concentration polarisation of ion-exchange particles in the conditions of Electrokinetic Phenomena of the second kind are analysed. It is shown that the theoretical model of concentration polarisation has to include the process of water dissociation. The region of parameters that corresponds to the maximum manifestation of water dissociation in Electrokinetic Phenomena is defined. The analysis of experimental results corroborated the correctness of the main statements of developed theory.
David B. Pengra - One of the best experts on this subject based on the ideXlab platform.
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Electrokinetic Phenomena in Porous Media
MRS Online Proceedings Library, 1995Co-Authors: David B. Pengra, Po-zen WongAbstract:Electrokinetic Phenomena, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming potential (the complementary process) are known to exist in brine-saturated porous media, but are very difficult to measure. With modern instrumentation and an ac method, we can now determine these transport coefficients accurately, and use them to characterize the permeability k, the effective throat radius R _ e , and the electric potential at the slip-plane, or ζ-potential. Our study shows that permeability can be determined by two different means: by combining the dc values of the streaming potential, electroosmotic pressure and conductivity; or from the frequency response of ac electroosmosis alone. The high sensitivity of the method allows us to measure k over the 0.1-10,000 millidarcy range with less than 10kPa applied pressure. This article reviews some of the basics of Electrokinetics and describes our methods. We also discuss effects of brine salinity and possible effects due to the fractal nature of the pore surface.
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Pore Size, Permeability and Electrokinetic Phenomena
Fundamental Materials Research, 1Co-Authors: Po-zen Wong, David B. PengraAbstract:In any application of porous materials, one is always concerned about the pore size and the hydraulic permeability of the material. The former determines the amount of internal surface area and the latter controls how easy fluids can access these pores. These two properties are closely related because the smaller the pores are, the harder it is for fluids to flow through the material. In catalytic materials, it is desirable to have small pores to increase the amount of surface area, but they must not be too small to let the reactants flow. Without some quantitative knowledge of how the pore size affects the permeability, it would be difficult to achieve an optimal compromise between the two competing factors. However, defining the meaning of pore size precisely and relating it to the permeability is nontrivial. The term pore size is commonly used in the study of porous media without a clear definition, because in most materials the pores have irregular shapes with features sizes that span a wide range of length scales. In the petroleum industry where one is concerned with the flow of hydrocarbons through the pores of sedimentary rock, studies have shown that the pores have features ranging from below one nanometer to tens of micrometers. Many experiments indicate that the pore surface in sedimentary rock exhibits the scale invariant behavior of fractals.1,2 For many of the catalytic materials described in this volume, the pore sizes are quite uniform and fall in the 1–10 nm range. However, the materials are made in the form of small particles and the inter-particle pores are irregular in shape and much larger in size, not very different from the ones in rock. For the reacting fluids to access the nanopores inside the particles, they have to flow through the macropores between the particles. In such systems with irregularly shaped pores or two distinct classes of pores, how can one define a unique pore size that governs the flow properties? This is the basic question we try to address in this article. Over the last decade, much effort has been directed towards a better quantification of the microgeometry of porous media and understanding how it affects the permeability.3 Many of these studies were carried out for sedimentary rock because the rock
Po-zen Wong - One of the best experts on this subject based on the ideXlab platform.
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Electrokinetic Phenomena in Porous Media
MRS Online Proceedings Library, 1995Co-Authors: David B. Pengra, Po-zen WongAbstract:Electrokinetic Phenomena, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming potential (the complementary process) are known to exist in brine-saturated porous media, but are very difficult to measure. With modern instrumentation and an ac method, we can now determine these transport coefficients accurately, and use them to characterize the permeability k, the effective throat radius R _ e , and the electric potential at the slip-plane, or ζ-potential. Our study shows that permeability can be determined by two different means: by combining the dc values of the streaming potential, electroosmotic pressure and conductivity; or from the frequency response of ac electroosmosis alone. The high sensitivity of the method allows us to measure k over the 0.1-10,000 millidarcy range with less than 10kPa applied pressure. This article reviews some of the basics of Electrokinetics and describes our methods. We also discuss effects of brine salinity and possible effects due to the fractal nature of the pore surface.
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Pore Size, Permeability and Electrokinetic Phenomena
Fundamental Materials Research, 1Co-Authors: Po-zen Wong, David B. PengraAbstract:In any application of porous materials, one is always concerned about the pore size and the hydraulic permeability of the material. The former determines the amount of internal surface area and the latter controls how easy fluids can access these pores. These two properties are closely related because the smaller the pores are, the harder it is for fluids to flow through the material. In catalytic materials, it is desirable to have small pores to increase the amount of surface area, but they must not be too small to let the reactants flow. Without some quantitative knowledge of how the pore size affects the permeability, it would be difficult to achieve an optimal compromise between the two competing factors. However, defining the meaning of pore size precisely and relating it to the permeability is nontrivial. The term pore size is commonly used in the study of porous media without a clear definition, because in most materials the pores have irregular shapes with features sizes that span a wide range of length scales. In the petroleum industry where one is concerned with the flow of hydrocarbons through the pores of sedimentary rock, studies have shown that the pores have features ranging from below one nanometer to tens of micrometers. Many experiments indicate that the pore surface in sedimentary rock exhibits the scale invariant behavior of fractals.1,2 For many of the catalytic materials described in this volume, the pore sizes are quite uniform and fall in the 1–10 nm range. However, the materials are made in the form of small particles and the inter-particle pores are irregular in shape and much larger in size, not very different from the ones in rock. For the reacting fluids to access the nanopores inside the particles, they have to flow through the macropores between the particles. In such systems with irregularly shaped pores or two distinct classes of pores, how can one define a unique pore size that governs the flow properties? This is the basic question we try to address in this article. Over the last decade, much effort has been directed towards a better quantification of the microgeometry of porous media and understanding how it affects the permeability.3 Many of these studies were carried out for sedimentary rock because the rock