{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/34563"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/34563","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Collective behavior of colloidal suspensions under electric fields and confinement","abstract":"Electrokinetic phenomena have been widely used in microfluidic devices as a means of manipulating fluids and particles. As a main area of interest in the present study, particle dynamics driven by electrokinetic phenomena in Stokes flow are investigated using theory and numerical simulations. In particular, we focus on the dynamics and collective behavior of colloidal suspensions of spherical particles under electric fields and confinement. We first analyze the nonlinear dynamics of non-colloidal, uncharged ideally polarizable spheres freely suspended in a viscous electrolyte in a uniform electric field. Specifically, we investigate two nonlinear electrokinetic effects, dielectrophoresis and induced-charge electrophoresis. While these phenomena yield no net motion in the case of a single uncharged sphere, they can drive relative motions by symmetry breaking when several particles are present. We perform large-scale simulations of such suspensions with periodic boundary conditions using an efficient simulation method. While the dynamics under dielectrophoresis alone are shown to be characterized by particle chaining along the field direction, chaining is not found to occur when induced-charge electrophoresis occurs as well, which instead causes transient particle pairings and results in a non-uniform microstructure with large number density fluctuations. We also present results on hydrodynamic dispersion and velocity fluctuations, and their dependence on volume fraction is discussed. We then pay attention to two special cases. First, colloidal suspensions of spheres undergoing dielectrophoresis alone in a uniform AC electric field under confinement are considered to investigate the long-time dynamics and pattern formation. Building on a previously developed algorithm with Brownian motion and steric interactions with rigid walls, we can probe a large range of time scales for the pattern formation in these suspensions. The rapid chain formation that occurs in the field direction as a result of dipolar interactions is found to be followed by a slow coarsening process by which chains coalesce into hexagonal sheets and eventually rearrange to form mesoscale cellular structures. Secondly, we investigate the effects of surface contamination, modeled as a thin dielectric coating, on the dynamics in suspensions of ideally polarizable spheres in an applied electric field using large-scale simulations. As surface contamination becomes significant, a transition from diffusive dynamics to sub-diffusive dynamics with local aggregation and chaining is shown to arise. This effect has a strong impact on the suspension microstructure as well as on particle velocities, which are strongly reduced for contaminated particles. As an application of these studies, we investigate electrophoretic deposition, a multiphysics phenomenon, as a method for the assembly of colloidal suspensions. Although the basic mechanisms in electrophoretic deposition are well-known and have been studied extensively, a detailed, quantitative model for the dynamics and kinetics is lacking, and is needed to optimize the deposition process. To this end, we develop a detailed model, and we implement a simulation method that captures the dynamics during the electrophoretic deposition process, with the aim of predicting deposit microstructures and assessing the precise influence of various parameters. We first present simulation results with uniform electrodes, where various analyses of the deposit microstructure are conducted. We then present results on the use of patterned electrodes for the manufacturing of more complex deposits. In addition, the simulation results presented are also directly compared to experimental observations for the validation of the models as well as for their improvement. Finally, we propose an efficient method for the calculation of hydrodynamic interactions between two parallel planar walls in Stokes flow. In this method, the problem is split into two parts. The first part corresponds to finding a periodic solution in the absence of the walls, for which efficient algorithms are applicable. The second part, called the auxiliary problem, aims to find an auxiliary solution to account for correction to the periodic solution for the two planar walls, when appropriate wall-boundary conditions are enforced at the walls. In particular, it is found that analytic solutions to the auxiliary problem can be obtained using a spectral method. This method will find a wide range of applications in the modeling of suspensions in confined geometries.","abstract_html":"Electrokinetic phenomena have been widely used in microfluidic devices as a means of manipulating fluids and particles. As a main area of interest in the present study, particle dynamics driven by electrokinetic phenomena in Stokes flow are investigated using theory and numerical simulations. In particular, we focus on the dynamics and collective behavior of colloidal suspensions of spherical particles under electric fields and confinement. We first analyze the nonlinear dynamics of non-colloidal, uncharged ideally polarizable spheres freely suspended in a viscous electrolyte in a uniform electric field. Specifically, we investigate two nonlinear electrokinetic effects, dielectrophoresis and induced-charge electrophoresis. While these phenomena yield no net motion in the case of a single uncharged sphere, they can drive relative motions by symmetry breaking when several particles are present. We perform large-scale simulations of such suspensions with periodic boundary conditions using an efficient simulation method. While the dynamics under dielectrophoresis alone are shown to be characterized by particle chaining along the field direction, chaining is not found to occur when induced-charge electrophoresis occurs as well, which instead causes transient particle pairings and results in a non-uniform microstructure with large number density fluctuations. We also present results on hydrodynamic dispersion and velocity fluctuations, and their dependence on volume fraction is discussed. We then pay attention to two special cases. First, colloidal suspensions of spheres undergoing dielectrophoresis alone in a uniform AC electric field under confinement are considered to investigate the long-time dynamics and pattern formation. Building on a previously developed algorithm with Brownian motion and steric interactions with rigid walls, we can probe a large range of time scales for the pattern formation in these suspensions. The rapid chain formation that occurs in the field direction as a result of dipolar interactions is found to be followed by a slow coarsening process by which chains coalesce into hexagonal sheets and eventually rearrange to form mesoscale cellular structures. Secondly, we investigate the effects of surface contamination, modeled as a thin dielectric coating, on the dynamics in suspensions of ideally polarizable spheres in an applied electric field using large-scale simulations. As surface contamination becomes significant, a transition from diffusive dynamics to sub-diffusive dynamics with local aggregation and chaining is shown to arise. This effect has a strong impact on the suspension microstructure as well as on particle velocities, which are strongly reduced for contaminated particles. As an application of these studies, we investigate electrophoretic deposition, a multiphysics phenomenon, as a method for the assembly of colloidal suspensions. Although the basic mechanisms in electrophoretic deposition are well-known and have been studied extensively, a detailed, quantitative model for the dynamics and kinetics is lacking, and is needed to optimize the deposition process. To this end, we develop a detailed model, and we implement a simulation method that captures the dynamics during the electrophoretic deposition process, with the aim of predicting deposit microstructures and assessing the precise influence of various parameters. We first present simulation results with uniform electrodes, where various analyses of the deposit microstructure are conducted. We then present results on the use of patterned electrodes for the manufacturing of more complex deposits. In addition, the simulation results presented are also directly compared to experimental observations for the validation of the models as well as for their improvement. Finally, we propose an efficient method for the calculation of hydrodynamic interactions between two parallel planar walls in Stokes flow. In this method, the problem is split into two parts. The first part corresponds to finding a periodic solution in the absence of the walls, for which efficient algorithms are applicable. The second part, called the auxiliary problem, aims to find an auxiliary solution to account for correction to the periodic solution for the two planar walls, when appropriate wall-boundary conditions are enforced at the walls. In particular, it is found that analytic solutions to the auxiliary problem can be obtained using a spectral method. This method will find a wide range of applications in the modeling of suspensions in confined geometries.","abstract_has_math":false,"creators":["Park, Jae Sung"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Saintillan, David","Higdon, Jonathan J.L.","Freund, Jonathan B.","Hilgenfeldt, Sascha","Olson, Luke N."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-09-18T21:25:44Z","date_published":"2012-09-18T21:25:44Z","updated_at":"2026-07-22T22:25:31Z","subjects":["Electrokinetics","Stokesian dynamics","Suspensions","Electrophoretic deposition"],"languages":["en"],"rights":["Copyright 2012 Jae Sung Park"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/34563","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Saintillan, David","Higdon, Jonathan J.L.","Freund, Jonathan B.","Hilgenfeldt, Sascha","Olson, Luke N."]},{"key":"dc:creator","label":"Author","values":["Park, Jae Sung"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012-09-18T21:25:44Z","2014-09-18T10:00:56Z","2012-08"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Electrokinetics","Stokesian dynamics","Suspensions","Electrophoretic deposition"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2012 Jae Sung Park"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/34563"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Electrokinetic phenomena have been widely used in microfluidic devices as a means of manipulating fluids and particles. As a main area of interest in the present study, particle dynamics driven by electrokinetic phenomena in Stokes flow are investigated using theory and numerical simulations. In particular, we focus on the dynamics and collective behavior of colloidal suspensions of spherical particles under electric fields and confinement. We first analyze the nonlinear dynamics of non-colloidal, uncharged ideally polarizable spheres freely suspended in a viscous electrolyte in a uniform electric field. Specifically, we investigate two nonlinear electrokinetic effects, dielectrophoresis and induced-charge electrophoresis. While these phenomena yield no net motion in the case of a single uncharged sphere, they can drive relative motions by symmetry breaking when several particles are present. We perform large-scale simulations of such suspensions with periodic boundary conditions using an efficient simulation method. While the dynamics under dielectrophoresis alone are shown to be characterized by particle chaining along the field direction, chaining is not found to occur when induced-charge electrophoresis occurs as well, which instead causes transient particle pairings and results in a non-uniform microstructure with large number density fluctuations. We also present results on hydrodynamic dispersion and velocity fluctuations, and their dependence on volume fraction is discussed. We then pay attention to two special cases. First, colloidal suspensions of spheres undergoing dielectrophoresis alone in a uniform AC electric field under confinement are considered to investigate the long-time dynamics and pattern formation. Building on a previously developed algorithm with Brownian motion and steric interactions with rigid walls, we can probe a large range of time scales for the pattern formation in these suspensions. The rapid chain formation that occurs in the field direction as a result of dipolar interactions is found to be followed by a slow coarsening process by which chains coalesce into hexagonal sheets and eventually rearrange to form mesoscale cellular structures. Secondly, we investigate the effects of surface contamination, modeled as a thin dielectric coating, on the dynamics in suspensions of ideally polarizable spheres in an applied electric field using large-scale simulations. As surface contamination becomes significant, a transition from diffusive dynamics to sub-diffusive dynamics with local aggregation and chaining is shown to arise. This effect has a strong impact on the suspension microstructure as well as on particle velocities, which are strongly reduced for contaminated particles. As an application of these studies, we investigate electrophoretic deposition, a multiphysics phenomenon, as a method for the assembly of colloidal suspensions. Although the basic mechanisms in electrophoretic deposition are well-known and have been studied extensively, a detailed, quantitative model for the dynamics and kinetics is lacking, and is needed to optimize the deposition process. To this end, we develop a detailed model, and we implement a simulation method that captures the dynamics during the electrophoretic deposition process, with the aim of predicting deposit microstructures and assessing the precise influence of various parameters. We first present simulation results with uniform electrodes, where various analyses of the deposit microstructure are conducted. We then present results on the use of patterned electrodes for the manufacturing of more complex deposits. In addition, the simulation results presented are also directly compared to experimental observations for the validation of the models as well as for their improvement. Finally, we propose an efficient method for the calculation of hydrodynamic interactions between two parallel planar walls in Stokes flow. In this method, the problem is split into two parts. The first part corresponds to finding a periodic solution in the absence of the walls, for which efficient algorithms are applicable. The second part, called the auxiliary problem, aims to find an auxiliary solution to account for correction to the periodic solution for the two planar walls, when appropriate wall-boundary conditions are enforced at the walls. In particular, it is found that analytic solutions to the auxiliary problem can be obtained using a spectral method. This method will find a wide range of applications in the modeling of suspensions in confined geometries.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2012-06-15T15:20:04Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Park_Jae Sung.pdf: 44218543 bytes, checksum: 04b4a6b997a25544798e11f7027e4620 (MD5)","Made available in DSpace on 2012-09-18T21:25:44Z (GMT). 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As a main area of interest in the present study, particle dynamics driven by electrokinetic phenomena in Stokes flow are investigated using theory and numerical simulations. In particular, we focus on the dynamics and collective behavior of colloidal suspensions of spherical particles under electric fields and confinement. We first analyze the nonlinear dynamics of non-colloidal, uncharged ideally polarizable spheres freely suspended in a viscous electrolyte in a uniform electric field. Specifically, we investigate two nonlinear electrokinetic effects, dielectrophoresis and induced-charge electrophoresis. While these phenomena yield no net motion in the case of a single uncharged sphere, they can drive relative motions by symmetry breaking when several particles are present. We perform large-scale simulations of such suspensions with periodic boundary conditions using an efficient simulation method. While the dynamics under dielectrophoresis alone are shown to be characterized by particle chaining along the field direction, chaining is not found to occur when induced-charge electrophoresis occurs as well, which instead causes transient particle pairings and results in a non-uniform microstructure with large number density fluctuations. We also present results on hydrodynamic dispersion and velocity fluctuations, and their dependence on volume fraction is discussed. We then pay attention to two special cases. First, colloidal suspensions of spheres undergoing dielectrophoresis alone in a uniform AC electric field under confinement are considered to investigate the long-time dynamics and pattern formation. Building on a previously developed algorithm with Brownian motion and steric interactions with rigid walls, we can probe a large range of time scales for the pattern formation in these suspensions. The rapid chain formation that occurs in the field direction as a result of dipolar interactions is found to be followed by a slow coarsening process by which chains coalesce into hexagonal sheets and eventually rearrange to form mesoscale cellular structures. Secondly, we investigate the effects of surface contamination, modeled as a thin dielectric coating, on the dynamics in suspensions of ideally polarizable spheres in an applied electric field using large-scale simulations. As surface contamination becomes significant, a transition from diffusive dynamics to sub-diffusive dynamics with local aggregation and chaining is shown to arise. This effect has a strong impact on the suspension microstructure as well as on particle velocities, which are strongly reduced for contaminated particles. As an application of these studies, we investigate electrophoretic deposition, a multiphysics phenomenon, as a method for the assembly of colloidal suspensions. Although the basic mechanisms in electrophoretic deposition are well-known and have been studied extensively, a detailed, quantitative model for the dynamics and kinetics is lacking, and is needed to optimize the deposition process. To this end, we develop a detailed model, and we implement a simulation method that captures the dynamics during the electrophoretic deposition process, with the aim of predicting deposit microstructures and assessing the precise influence of various parameters. We first present simulation results with uniform electrodes, where various analyses of the deposit microstructure are conducted. We then present results on the use of patterned electrodes for the manufacturing of more complex deposits. In addition, the simulation results presented are also directly compared to experimental observations for the validation of the models as well as for their improvement. Finally, we propose an efficient method for the calculation of hydrodynamic interactions between two parallel planar walls in Stokes flow. In this method, the problem is split into two parts. The first part corresponds to finding a periodic solution in the absence of the walls, for which efficient algorithms are applicable. The second part, called the auxiliary problem, aims to find an auxiliary solution to account for correction to the periodic solution for the two planar walls, when appropriate wall-boundary conditions are enforced at the walls. In particular, it is found that analytic solutions to the auxiliary problem can be obtained using a spectral method. This method will find a wide range of applications in the modeling of suspensions in confined geometries.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2012-06-15T15:20:04Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Park_Jae Sung.pdf: 44218543 bytes, checksum: 04b4a6b997a25544798e11f7027e4620 (MD5)","Made available in DSpace on 2012-09-18T21:25:44Z (GMT). No. of bitstreams: 2 Park_JaeSung.pdf: 44218542 bytes, checksum: 74e466d12235b4d3ed382c7279b9db24 (MD5) license.txt: 4056 bytes, checksum: 65778a2c1c434698859517877678e630 (MD5)","Restriction data tranferred 2014-07-01T11:35:50-05:00 Original Data Group with Access Administrator Release Date: 2014-09-18 16:27:16 UTC Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Item marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins (srobbins@illinois.edu) on 2012-09-18T21:27:31Z Item is restricted until 2014-09-18T21:27:16Z","Limited Restriction Lifted for Item 34837 on 2014-09-18T10:00:56Z."],"dc:identifier":["http://hdl.handle.net/2142/34563"],"dc:language":["en"],"dc:rights":["Copyright 2012 Jae Sung Park"],"dc:subject":["Electrokinetics","Stokesian dynamics","Suspensions","Electrophoretic deposition"],"dc:title":["Collective behavior of colloidal suspensions under electric fields and confinement"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:31Z"}