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Nguyen DB, Ha VP, Vuong VD, Chien YH, Le TV, Chu CY. Simulation and Verification of the Direct Current Electric Field on Fabricating High Porosity f-MWCNTs Thin Films by Electrophoretic Deposition Technique. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3883-3894. [PMID: 36898055 DOI: 10.1021/acs.langmuir.2c03116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Electrophoretic deposition (EPD) is the potential process in high porosity thin films' fabrication or complex surface coating for perovskite photovoltaics. Here, the electrostatic simulation is introduced to optimize the EPD cell design for the cathodic EPD process based on functionalized multiwalled carbon nanotubes (f-MWCNTs). The similarity between the thin film structure and the electric field simulation is evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) results. The thin-film surface at the edge has a higher roughness (Ra) compared to the center position (16.48 > 10.26 nm). The f-MWCNTs at the edge position tend to be twisted and bent due to the torque of the electric field. The Raman results show that f-MWCNTs with low defect density are more easily to be positively charged and deposited on the ITO surface. The distribution of oxygen and aluminum atoms in the thin film reveals that the aluminum atoms tend to have adsorption/electrostatic attraction to the interlayer defect positions of f-MWCNTs without individually depositing onto the cathode. Finally, this study can reduce the cost and time for the scale-up process by optimizing the input parameters for the complete cathodic electrophoretic deposition process through electric field inspection.
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Affiliation(s)
- Duc-Binh Nguyen
- Department of Materials Science and Engineering, Feng Chia University, Taichung City, 40724, Taiwan
- Institute of Green Products, Feng Chia University, Taichung City, 40724, Taiwan
| | - Vinh-Phuc Ha
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, 740500, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, 740500, Vietnam
| | - Vinh-Dat Vuong
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, 740500, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, 740500, Vietnam
| | - Yi-Hsin Chien
- Department of Materials Science and Engineering, Feng Chia University, Taichung City, 40724, Taiwan
| | - Thang Van Le
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, 740500, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, 740500, Vietnam
| | - Chen-Yeon Chu
- Institute of Green Products, Feng Chia University, Taichung City, 40724, Taiwan
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Vigh G, Gaš B. Evolution of the theoretical description of the isoelectric focusing experiment: II. An open system isoelectric focusing experiment is a transient, bidirectional isotachophoretic experiment. Electrophoresis 2023; 44:675-688. [PMID: 36641504 DOI: 10.1002/elps.202200238] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/29/2022] [Accepted: 01/05/2023] [Indexed: 01/16/2023]
Abstract
The carrier ampholytes-based (CA-based) isoelectric focusing (IEF) experiment evolved from Svensson's closed system IEF (constant spatial current density, absence of convective mixing, counter-balancing electrophoretic and diffusive fluxes yielding a steady state pH gradient) to the contemporary open system IEF (absence of convective mixing, large cross-sectional area electrode vessels, lack of counter-balancing electrophoretic- and diffusive fluxes leading to transient pH gradients). Open system IEF currently is described by a two-stage model: In the first stage, a rapid IEF process forms the pH gradient which, in the second stage, is slowly degraded by isotachophoretic processes that move the most acidic and most basic CAs into the electrode vessels. An analysis of the effective mobilities and the effective mobility to conductivity ratios of the anolyte, catholyte, and the CAs indicates that in open system IEF experiments a single process, transient bidirectional isotachophoresis (tbdITP) operates from the moment current is turned on until it is turned off. In tbdITP, the anolyte and catholyte provide the leading ions and the pI 7 CA or the reactive boundary of the counter-migrating H3 O+ and OH- ions serves as the shared terminator. The outcome of the tbdITP process is determined by the ionic mobilities, pKa values, and loaded amounts of all ionic and ionizable components: It is constrained by both the transmitted amount of charge and the migration space available for the leading ions. tbdITP and the resulting pH gradient can never reach steady state with respect to the spatial coordinate of the separation channel.
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Affiliation(s)
- Gyula Vigh
- Chemistry Department, Texas A&M University, College Station, Texas, USA
| | - Bohuslav Gaš
- Faculty of Science, Charles University, Prague, Czech Republic
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Abstract
Isotachophoresis (ITP) is a versatile electrophoretic technique that can be used for sample preconcentration, separation, purification, and mixing, and to control and accelerate chemical reactions. Although the basic technique is nearly a century old and widely used, there is a persistent need for an easily approachable, succinct, and rigorous review of ITP theory and analysis. This is important because the interest and adoption of the technique has grown over the last two decades, especially with its implementation in microfluidics and integration with on-chip chemical and biochemical assays. We here provide a review of ITP theory starting from physicochemical first-principles, including conservation of species, conservation of current, approximation of charge neutrality, pH equilibrium of weak electrolytes, and so-called regulating functions that govern transport dynamics, with a strong emphasis on steady and unsteady transport. We combine these generally applicable (to all types of ITP) theoretical discussions with applications of ITP in the field of microfluidic systems, particularly on-chip biochemical analyses. Our discussion includes principles that govern the ITP focusing of weak and strong electrolytes; ITP dynamics in peak and plateau modes; a review of simulation tools, experimental tools, and detection methods; applications of ITP for on-chip separations and trace analyte manipulation; and design considerations and challenges for microfluidic ITP systems. We conclude with remarks on possible future research directions. The intent of this review is to help make ITP analysis and design principles more accessible to the scientific and engineering communities and to provide a rigorous basis for the increased adoption of ITP in microfluidics.
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Affiliation(s)
- Ashwin Ramachandran
- Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, United States
| | - Juan G Santiago
- Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States
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Thormann W, Mosher RA. Dynamic computer simulations of electrophoresis: 2010-2020. Electrophoresis 2021; 43:10-36. [PMID: 34287996 PMCID: PMC9292373 DOI: 10.1002/elps.202100191] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/12/2021] [Accepted: 07/15/2021] [Indexed: 02/05/2023]
Abstract
The transport of components in liquid media under the influence of an applied electric field can be described with the continuity equation. It represents a nonlinear conservation law that is based upon the balance laws of continuous transport processes and can be solved in time and space numerically. This procedure is referred to as dynamic computer simulation. Since its inception four decades ago, the state of dynamic computer simulation software and its use has progressed significantly. Dynamic models are the most versatile tools to explore the fundamentals of electrokinetic separations and provide insights into the behavior of buffer systems and sample components of all electrophoretic separation methods, including moving boundary electrophoresis, CZE, CGE, ITP, IEF, EKC, ACE, and CEC. This article is a continuation of previous reviews (Electrophoresis 2009, 30, S16–S26 and Electrophoresis 2010, 31, 726–754) and summarizes the progress and achievements made during the 2010 to 2020 time period in which some of the existing dynamic simulators were extended and new simulation packages were developed. This review presents the basics and extensions of the three most used one‐dimensional simulators, provides a survey of new one‐dimensional simulators, outlines an overview of multi‐dimensional models, and mentions models that were briefly reported in the literature. A comprehensive discussion of simulation applications and achievements of the 2010 to 2020 time period is also included.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Gaš B, Bravenec P. Simul 6: A fast dynamic simulator of electromigration. Electrophoresis 2021; 42:1291-1299. [PMID: 33811678 DOI: 10.1002/elps.202100048] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/22/2021] [Accepted: 03/26/2021] [Indexed: 11/09/2022]
Abstract
Simul 6 is a 1D dynamic simulator of electromigration based on the mathematical model of electromigration in free solutions. The model consists of continuity equations for the movement of electrolytes in a separation channel, acid-base equilibria of weak electrolytes, and the electroneutrality condition. It accounts for any number of multivalent electrolytes or ampholytes and provides a complete picture about dynamics of electromigration and diffusion in the separation channel. The equations are solved numerically using software means which allow for parallelization and multithreaded computation. Simul 6 has a user-friendly graphical interface. It is typically used for inspection of system peaks (zones) in electrophoresis, stacking and preconcentrating analytes, optimization of separation conditions, method development in either capillary zone electrophoresis, isotachophoresis, and isoelectric focusing. Simul 6 is the successor of Simul 5, and has been launched as a free software available for download at https://simul6.app/.
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Affiliation(s)
- Bohuslav Gaš
- Faculty of Science, Department of Physical and Macromolecular Chemistry, Charles University in Prague, Prague, Czech Republic
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Thormann W, Mosher RA. Instabilities of the pH gradient in carrier ampholyte-based isoelectric focusing: Elucidation of the contributing electrokinetic processes by computer simulation. Electrophoresis 2020; 42:814-833. [PMID: 33184847 DOI: 10.1002/elps.202000269] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/22/2020] [Accepted: 11/05/2020] [Indexed: 11/05/2022]
Abstract
Electrokinetic processes that lead to pH gradient instabilities in carrier ampholyte-based IEF are reviewed. In addition to electroosmosis, there are four of electrophoretic nature, namely (i) the stabilizing phase with the plateau phenomenon, (ii) the gradual isotachophoretic loss of carrier ampholytes at the two column ends in presence of electrode solutions, (iii) the inequality of the mobilities of positively and negatively charged species of ampholytes, and (iv) the continuous penetration of carbonate from the catholyte into the focusing column. The impact of these factors to cathodic and anodic drifts was analyzed by simulation of carrier ampholyte-based focusing in closed and open columns. Focusing under realistic conditions within a 5 cm long capillary in which three amphoteric low molecular mass dyes were focused in a pH 3-10 gradient formed by 140 carrier ampholytes was investigated. In open columns, electroosmosis displaces the entire gradient toward the cathode or anode whereas the electrophoretic processes act bidirectionally with a transition around pH 4 (drifts for pI > 4 and pI < 4 typically toward the cathode and anode, respectively). The data illustrate that focused zones of carrier ampholytes have an electrophoretic flux and that dynamic simulation can be effectively used to assess the magnitude of each of the electrokinetic destabilizing factors and the resulting drift for a combination of these effects. Predicted drifts of focused marker dyes are compared to those observed experimentally in a setup with coated capillary and whole column optical imaging.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Šalplachta J, Horká M, Šlais K. Preparative isoelectric focusing in a cellulose-based separation medium. J Sep Sci 2017; 40:2498-2505. [PMID: 28432777 DOI: 10.1002/jssc.201700036] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/04/2017] [Accepted: 04/10/2017] [Indexed: 01/04/2023]
Abstract
An improved preparative method based on isoelectric focusing of analytes in a cellulose-based separation medium is described in this study. Cellulose is suspended in an aqueous solution of simple buffers, ethylene glycol, glycerol, nonionic surfactant, and colored pI markers. Water partially evaporates during focusing run and the separation takes place in an in situ generated layer of cellulose, which has a gel-like appearance at the end of analysis. Final positions of analytes are indicated by the positions of zones of focused pI markers. Fractions, segments of the separation medium with analytes, can be simply collected by spatula and analyzed by downstream analytical methods. Good focusing ability of the new method and almost quantitative recovery of model proteins, cytochrome c and bovine serum albumin, was verified by gel electrophoresis and capillary isoelectric focusing of the collected fractions.
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Affiliation(s)
- Jiří Šalplachta
- Institute of Analytical Chemistry of the CAS, Brno, Czech Republic
| | - Marie Horká
- Institute of Analytical Chemistry of the CAS, Brno, Czech Republic
| | - Karel Šlais
- Institute of Analytical Chemistry of the CAS, Brno, Czech Republic
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New solution IEF device for micropreparative separation of peptides and proteins. Electrophoresis 2013; 34:1519-25. [DOI: 10.1002/elps.201200485] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/17/2012] [Accepted: 12/27/2012] [Indexed: 11/07/2022]
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Bahga SS, Bercovici M, Santiago JG. Robust and high-resolution simulations of nonlinear electrokinetic processes in variable cross-section channels. Electrophoresis 2012; 33:3036-51. [DOI: 10.1002/elps.201200264] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/30/2012] [Accepted: 07/09/2012] [Indexed: 11/06/2022]
Affiliation(s)
- Supreet S. Bahga
- Department of Mechanical Engineering; Stanford University; CA; USA
| | - Moran Bercovici
- Faculty of Mechanical Engineering; Technion-Israel Institute of Technology; Haifa; Israel
| | - Juan G. Santiago
- Department of Mechanical Engineering; Stanford University; CA; USA
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Hruška V, Beneš M, Svobodová J, Zusková I, Gaš B. Simulation of the effects of complex- formation equilibria in electrophoresis: I. Mathematical model. Electrophoresis 2012; 33:938-47. [DOI: 10.1002/elps.201100529] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Martin Beneš
- Faculty of Science, Department of Physical and Macromolecular Chemistry; Charles University in Prague; Prague; Czech Republic
| | - Jana Svobodová
- Faculty of Science, Department of Physical and Macromolecular Chemistry; Charles University in Prague; Prague; Czech Republic
| | - Iva Zusková
- Faculty of Science, Department of Physical and Macromolecular Chemistry; Charles University in Prague; Prague; Czech Republic
| | - Bohuslav Gaš
- Faculty of Science, Department of Physical and Macromolecular Chemistry; Charles University in Prague; Prague; Czech Republic
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Mosher RA, Breadmore MC, Thormann W. High-resolution electrophoretic simulations: Performance characteristics of one-dimensional simulators. Electrophoresis 2011; 32:532-41. [DOI: 10.1002/elps.201000517] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 10/05/2010] [Accepted: 10/19/2010] [Indexed: 11/10/2022]
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12
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Bahga SS, Kaigala GV, Bercovici M, Santiago JG. High-sensitivity detection using isotachophoresis with variable cross-section geometry. Electrophoresis 2011; 32:563-72. [DOI: 10.1002/elps.201000338] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 11/26/2010] [Accepted: 11/28/2010] [Indexed: 01/15/2023]
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Bottenus D, Jubery TZ, Dutta P, Ivory CF. 10,000-fold concentration increase in proteins in a cascade microchip using anionic ITP by a 3-D numerical simulation with experimental results. Electrophoresis 2011; 32:550-62. [PMID: 21308695 PMCID: PMC3229181 DOI: 10.1002/elps.201000510] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 12/02/2010] [Accepted: 12/05/2010] [Indexed: 11/07/2022]
Abstract
This paper describes both the experimental application and 3-D numerical simulation of isotachophoresis (ITP) in a 3.2 cm long "cascade" poly(methyl methacrylate) (PMMA) microfluidic chip. The microchip includes 10 × reductions in both the width and depth of the microchannel, which decreases the overall cross-sectional area by a factor of 100 between the inlet (cathode) and outlet (anode). A 3-D numerical simulation of ITP is outlined and is a first example of an ITP simulation in three dimensions. The 3-D numerical simulation uses COMSOL Multiphysics v4.0a to concentrate two generic proteins and monitor protein migration through the microchannel. In performing an ITP simulation on this microchip platform, we observe an increase in concentration by over a factor of more than 10,000 due to the combination of ITP stacking and the reduction in cross-sectional area. Two fluorescent proteins, green fluorescent protein and R-phycoerythrin, were used to experimentally visualize ITP through the fabricated microfluidic chip. The initial concentration of each protein in the sample was 1.995 μg/mL and, after preconcentration by ITP, the final concentrations of the two fluorescent proteins were 32.57 ± 3.63 and 22.81 ± 4.61 mg/mL, respectively. Thus, experimentally the two fluorescent proteins were concentrated by over a factor of 10,000 and show good qualitative agreement with our simulation results.
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Affiliation(s)
- Danny Bottenus
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA
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Thormann W, Breadmore MC, Caslavska J, Mosher RA. Dynamic computer simulations of electrophoresis: A versatile research and teaching tool. Electrophoresis 2010; 31:726-54. [DOI: 10.1002/elps.200900613] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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