{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/85536"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/85536","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Nonlinear ion concentration polarization : fundamentals and applications","abstract":"Ion exchange membrane (IEM) is a functional material that has a permselectivity of ions. Two types of IEMs - anion exchange membrane (AEM) and cation exchange membrane (CEM) - are used in a variety of electrochemical systems. Ion concentration polarization (ICP) is an ion transport phenomenon that occurs when ions selectively pass through IEMs. Recently, ICP has drawn renewed attention from physicists and engineers, due to its importance in understanding various electrochemical processes for biosensing, desalination, and energy devices. One of the significant scientific issues in ICP is the source of overlimiting conductance (OLC); even after the diffusion-limited current is achieved and nearly all ions are rejected from the IEM (reaching the so-called 'limiting current'), the current starts to increase again at a sufficiently high bias voltage. This nonlinearity of ICP has been extensively studied, but the complexity of this multiscale, multiphysic phenomenon makes it challenging to a fully-detailed picture. My Ph.D thesis is focused at the fundamental understanding and new engineering applications of nonlinear ICP. In this thesis, we consider four subjects: i) visualization of nonlinear ICP and its effects in electrodialysis (ED), ii) electroconvection (EC) as a source of OLC and its behaviors under shear flow, iii) study of water desalination process by ICP and its performance compared with ED, and iv) development of high-throughput, continuous-flow bio-agent preconcentrator by ICP. First, we describe the microscale ED model system for studying nonlinear ICP, which is used for visualizing in situ fluid flows and concentration profiles near IEMs. We verify that the nonlinear ICP largely determines ion transport in ED system. Interesting trends and insights are revealed, which will help in clarifying scientific issues regarding ED operation and improving the efficiency. Second, with this ability to visualize ICP, we firmly establish EC as the mechanism for OLC in the realistic ED system; EC exists near the both IEMs of standard ED systems, and it enhances ion flux through the membranes. We also characterize EC under shear flow by both experiments and numerical modeling. To the best of our knowledge, this characterization is the first to show the unique behaviors of sheared EC: unidirectional vortex structure, its height selection, and vortex advection. Next, based on understandings on sheared EC, we develop robust ICP desalination platform for more scalable (portable) and efficient device to remove salt ions. Utilizing nonlinear ICP between two identical IEMs, we can relocate salt ions along a specific portion of fluidic channels, generating brine and desalted flows in one channel. The salt removal ratio in this ICP desalination platform can be predicted by calculating the sheared EC's height. Also, we reveal the additional effects of nonlinear ICP on desalination process, which is quantified here for the first time, by comparison of salt removal ratio, energy consumption, and current efficiency between ICP platform with CEMs, AEMs, and ED system. In overlimiting regime, one achieves higher (lower) current efficiency compared with ED, when the mobility of relocating ions (e.g. anion at CEMs) is higher (lower) than that of conducting ions (e.g. cation at CEMs). Last, we present a new application utilizing nonlinear ICP, i.e. continuous-flow bio-agent preconcentrator. By controlling the nonlinear ICP region with a pressure gradient against the electric field, we concentrate variously charged bio-agents (e.g., positively / negatively-charged proteins, bacteria, and cells) on the ICP boundary, and collect these pre-concentrated targets in a continuous-flow manner.","abstract_html":"Ion exchange membrane (IEM) is a functional material that has a permselectivity of ions. Two types of IEMs - anion exchange membrane (AEM) and cation exchange membrane (CEM) - are used in a variety of electrochemical systems. Ion concentration polarization (ICP) is an ion transport phenomenon that occurs when ions selectively pass through IEMs. Recently, ICP has drawn renewed attention from physicists and engineers, due to its importance in understanding various electrochemical processes for biosensing, desalination, and energy devices. One of the significant scientific issues in ICP is the source of overlimiting conductance (OLC); even after the diffusion-limited current is achieved and nearly all ions are rejected from the IEM (reaching the so-called 'limiting current'), the current starts to increase again at a sufficiently high bias voltage. This nonlinearity of ICP has been extensively studied, but the complexity of this multiscale, multiphysic phenomenon makes it challenging to a fully-detailed picture. My Ph.D thesis is focused at the fundamental understanding and new engineering applications of nonlinear ICP. In this thesis, we consider four subjects: i) visualization of nonlinear ICP and its effects in electrodialysis (ED), ii) electroconvection (EC) as a source of OLC and its behaviors under shear flow, iii) study of water desalination process by ICP and its performance compared with ED, and iv) development of high-throughput, continuous-flow bio-agent preconcentrator by ICP. First, we describe the microscale ED model system for studying nonlinear ICP, which is used for visualizing in situ fluid flows and concentration profiles near IEMs. We verify that the nonlinear ICP largely determines ion transport in ED system. Interesting trends and insights are revealed, which will help in clarifying scientific issues regarding ED operation and improving the efficiency. Second, with this ability to visualize ICP, we firmly establish EC as the mechanism for OLC in the realistic ED system; EC exists near the both IEMs of standard ED systems, and it enhances ion flux through the membranes. We also characterize EC under shear flow by both experiments and numerical modeling. To the best of our knowledge, this characterization is the first to show the unique behaviors of sheared EC: unidirectional vortex structure, its height selection, and vortex advection. Next, based on understandings on sheared EC, we develop robust ICP desalination platform for more scalable (portable) and efficient device to remove salt ions. Utilizing nonlinear ICP between two identical IEMs, we can relocate salt ions along a specific portion of fluidic channels, generating brine and desalted flows in one channel. The salt removal ratio in this ICP desalination platform can be predicted by calculating the sheared EC's height. Also, we reveal the additional effects of nonlinear ICP on desalination process, which is quantified here for the first time, by comparison of salt removal ratio, energy consumption, and current efficiency between ICP platform with CEMs, AEMs, and ED system. In overlimiting regime, one achieves higher (lower) current efficiency compared with ED, when the mobility of relocating ions (e.g. anion at CEMs) is higher (lower) than that of conducting ions (e.g. cation at CEMs). Last, we present a new application utilizing nonlinear ICP, i.e. continuous-flow bio-agent preconcentrator. By controlling the nonlinear ICP region with a pressure gradient against the electric field, we concentrate variously charged bio-agents (e.g., positively / negatively-charged proteins, bacteria, and cells) on the ICP boundary, and collect these pre-concentrated targets in a continuous-flow manner.","abstract_has_math":false,"creators":["Kwak, Rhokyun"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Mechanical Engineering.","school":null,"contributors":[],"advisors":["Jongyoon Han."],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013","date_published":"2013","updated_at":"2026-07-22T22:22:22Z","subjects":["Mechanical Engineering."],"languages":["eng"],"rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/85536","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Jongyoon Han."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Department of Mechanical Engineering."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. Department of Mechanical Engineering."]},{"key":"dc:creator","label":"Author","values":["Kwak, Rhokyun"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-06T15:49:14Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-06T15:49:14Z"]},{"key":"dc:date.issued","label":"Date","values":["2013"]},{"key":"dc:publisher","label":"Institution","values":["Massachusetts Institute of Technology"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Mechanical Engineering."]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1721.1/85536"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.","Cataloged from PDF version of thesis.","Includes bibliographical references."]},{"key":"dc:description.abstract","label":"Abstract","values":["Ion exchange membrane (IEM) is a functional material that has a permselectivity of ions. Two types of IEMs - anion exchange membrane (AEM) and cation exchange membrane (CEM) - are used in a variety of electrochemical systems. Ion concentration polarization (ICP) is an ion transport phenomenon that occurs when ions selectively pass through IEMs. Recently, ICP has drawn renewed attention from physicists and engineers, due to its importance in understanding various electrochemical processes for biosensing, desalination, and energy devices. One of the significant scientific issues in ICP is the source of overlimiting conductance (OLC); even after the diffusion-limited current is achieved and nearly all ions are rejected from the IEM (reaching the so-called 'limiting current'), the current starts to increase again at a sufficiently high bias voltage. This nonlinearity of ICP has been extensively studied, but the complexity of this multiscale, multiphysic phenomenon makes it challenging to a fully-detailed picture. My Ph.D thesis is focused at the fundamental understanding and new engineering applications of nonlinear ICP. In this thesis, we consider four subjects: i) visualization of nonlinear ICP and its effects in electrodialysis (ED), ii) electroconvection (EC) as a source of OLC and its behaviors under shear flow, iii) study of water desalination process by ICP and its performance compared with ED, and iv) development of high-throughput, continuous-flow bio-agent preconcentrator by ICP. First, we describe the microscale ED model system for studying nonlinear ICP, which is used for visualizing in situ fluid flows and concentration profiles near IEMs. We verify that the nonlinear ICP largely determines ion transport in ED system. Interesting trends and insights are revealed, which will help in clarifying scientific issues regarding ED operation and improving the efficiency. Second, with this ability to visualize ICP, we firmly establish EC as the mechanism for OLC in the realistic ED system; EC exists near the both IEMs of standard ED systems, and it enhances ion flux through the membranes. We also characterize EC under shear flow by both experiments and numerical modeling. To the best of our knowledge, this characterization is the first to show the unique behaviors of sheared EC: unidirectional vortex structure, its height selection, and vortex advection. Next, based on understandings on sheared EC, we develop robust ICP desalination platform for more scalable (portable) and efficient device to remove salt ions. Utilizing nonlinear ICP between two identical IEMs, we can relocate salt ions along a specific portion of fluidic channels, generating brine and desalted flows in one channel. The salt removal ratio in this ICP desalination platform can be predicted by calculating the sheared EC's height. Also, we reveal the additional effects of nonlinear ICP on desalination process, which is quantified here for the first time, by comparison of salt removal ratio, energy consumption, and current efficiency between ICP platform with CEMs, AEMs, and ED system. In overlimiting regime, one achieves higher (lower) current efficiency compared with ED, when the mobility of relocating ions (e.g. anion at CEMs) is higher (lower) than that of conducting ions (e.g. cation at CEMs). Last, we present a new application utilizing nonlinear ICP, i.e. continuous-flow bio-agent preconcentrator. By controlling the nonlinear ICP region with a pressure gradient against the electric field, we concentrate variously charged bio-agents (e.g., positively / negatively-charged proteins, bacteria, and cells) on the ICP boundary, and collect these pre-concentrated targets in a continuous-flow manner."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:title","label":"Title","values":["Nonlinear ion concentration polarization : fundamentals and applications"]}]}],"canonical_facts":{"dc:contributor.advisor":["Jongyoon Han."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Mechanical Engineering."],"dc:contributor.other":["Massachusetts Institute of Technology. Department of Mechanical Engineering."],"dc:creator":["Kwak, Rhokyun"],"dc:date.accessioned":["2014-03-06T15:49:14Z"],"dc:date.available":["2014-03-06T15:49:14Z"],"dc:date.issued":["2013"],"dc:description":["Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.","Cataloged from PDF version of thesis.","Includes bibliographical references."],"dc:description.abstract":["Ion exchange membrane (IEM) is a functional material that has a permselectivity of ions. Two types of IEMs - anion exchange membrane (AEM) and cation exchange membrane (CEM) - are used in a variety of electrochemical systems. Ion concentration polarization (ICP) is an ion transport phenomenon that occurs when ions selectively pass through IEMs. Recently, ICP has drawn renewed attention from physicists and engineers, due to its importance in understanding various electrochemical processes for biosensing, desalination, and energy devices. One of the significant scientific issues in ICP is the source of overlimiting conductance (OLC); even after the diffusion-limited current is achieved and nearly all ions are rejected from the IEM (reaching the so-called 'limiting current'), the current starts to increase again at a sufficiently high bias voltage. This nonlinearity of ICP has been extensively studied, but the complexity of this multiscale, multiphysic phenomenon makes it challenging to a fully-detailed picture. My Ph.D thesis is focused at the fundamental understanding and new engineering applications of nonlinear ICP. In this thesis, we consider four subjects: i) visualization of nonlinear ICP and its effects in electrodialysis (ED), ii) electroconvection (EC) as a source of OLC and its behaviors under shear flow, iii) study of water desalination process by ICP and its performance compared with ED, and iv) development of high-throughput, continuous-flow bio-agent preconcentrator by ICP. First, we describe the microscale ED model system for studying nonlinear ICP, which is used for visualizing in situ fluid flows and concentration profiles near IEMs. We verify that the nonlinear ICP largely determines ion transport in ED system. Interesting trends and insights are revealed, which will help in clarifying scientific issues regarding ED operation and improving the efficiency. Second, with this ability to visualize ICP, we firmly establish EC as the mechanism for OLC in the realistic ED system; EC exists near the both IEMs of standard ED systems, and it enhances ion flux through the membranes. We also characterize EC under shear flow by both experiments and numerical modeling. To the best of our knowledge, this characterization is the first to show the unique behaviors of sheared EC: unidirectional vortex structure, its height selection, and vortex advection. Next, based on understandings on sheared EC, we develop robust ICP desalination platform for more scalable (portable) and efficient device to remove salt ions. Utilizing nonlinear ICP between two identical IEMs, we can relocate salt ions along a specific portion of fluidic channels, generating brine and desalted flows in one channel. The salt removal ratio in this ICP desalination platform can be predicted by calculating the sheared EC's height. Also, we reveal the additional effects of nonlinear ICP on desalination process, which is quantified here for the first time, by comparison of salt removal ratio, energy consumption, and current efficiency between ICP platform with CEMs, AEMs, and ED system. In overlimiting regime, one achieves higher (lower) current efficiency compared with ED, when the mobility of relocating ions (e.g. anion at CEMs) is higher (lower) than that of conducting ions (e.g. cation at CEMs). Last, we present a new application utilizing nonlinear ICP, i.e. continuous-flow bio-agent preconcentrator. By controlling the nonlinear ICP region with a pressure gradient against the electric field, we concentrate variously charged bio-agents (e.g., positively / negatively-charged proteins, bacteria, and cells) on the ICP boundary, and collect these pre-concentrated targets in a continuous-flow manner."],"dc:description.degree":["Ph. D."],"dc:identifier.uri":["http://hdl.handle.net/1721.1/85536"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Mechanical Engineering."],"dc:title":["Nonlinear ion concentration polarization : fundamentals and applications"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:22:22Z"}