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Chun Yang - One of the best experts on this subject based on the ideXlab platform.
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Electrokinetics of non newtonian fluids a review
Advances in Colloid and Interface Science, 2013Co-Authors: Cunlu Zhao, Chun YangAbstract:Abstract This work presents a comprehensive review of Electrokinetics pertaining to non-Newtonian fluids. The topic covers a broad range of non-Newtonian effects in Electrokinetics, including electroosmosis of non-Newtonian fluids, electrophoresis of particles in non-Newtonian fluids, streaming potential effect of non-Newtonian fluids and other related non-Newtonian effects in Electrokinetics. Generally, the coupling between non-Newtonian hydrodynamics and electrostatics not only complicates the Electrokinetics but also causes the fluid/particle velocity to be nonlinearly dependent on the strength of external electric field and/or the zeta potential. Shear-thinning nature of liquids tends to enhance electrokinetic phenomena, while shear-thickening nature of liquids leads to the reduction of electrokinetic effects. In addition, directions for the future studies are suggested and several theoretical issues in non-Newtonian Electrokinetics are highlighted.
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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.
Juan G Santiago - One of the best experts on this subject based on the ideXlab platform.
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basic principles of electrolyte chemistry for microfluidic Electrokinetics part i acid base equilibria and ph buffers
Lab on a Chip, 2009Co-Authors: Alexandre Persat, Robert D Chambers, Juan G SantiagoAbstract:We review fundamental and applied acid–base equilibrium chemistry useful to microfluidic Electrokinetics. We present elements of acid–base equilibrium reactions and derive rules for pH calculation for simple buffers. We also present a general formulation to calculate pH of more complex, arbitrary mixtures of electrolytes, and discuss the effects of ionic strength and temperature on pH calculation. More practically, we offer advice on buffer preparation and on buffer reporting. We also discuss “real world” buffers and likely contamination sources. In particular, we discuss the effects of atmospheric carbon dioxide on buffer systems, namely, the increase in ionic strength and acidification of typical electrokinetic device buffers. In Part II of this two-paper series, we discuss the coupling of acid–base equilibria with electrolyte dynamics and electrochemistry in typical microfluidic electrokinetic systems.
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basic principles of electrolyte chemistry for microfluidic Electrokinetics part ii coupling between ion mobility electrolysis and acid base equilibria
Lab on a Chip, 2009Co-Authors: Alexandre Persat, Matthew E Suss, Juan G SantiagoAbstract:We present elements of electrolyte dynamics and electrochemistry relevant to microfluidic Electrokinetics experiments. In Part I of this two-paper series, we presented a review and introduction to the fundamentals of acid–base chemistry. Here, we first summarize the coupling between acid–base equilibrium chemistry and electrophoretic mobilities of electrolytes, at both infinite and finite dilution. We then discuss the effects of electrode reactions on microfluidic electrokinetic experiments and derive a model for pH changes in microchip reservoirs during typical direct-current electrokinetic experiments. We present a model for the potential drop in typical microchip electrophoresis device. The latter includes finite element simulation to estimate the relative effects of channel and reservoir dimensions. Finally, we summarize effects of electrode and electrolyte characteristics on potential drop in microfluidic devices. As a whole, the discussions highlight the importance of the coupling between electromigration and electrophoresis, acid–base equilibria, and electrochemical reactions.
Cunlu Zhao - One of the best experts on this subject based on the ideXlab platform.
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Electrokinetics of non newtonian fluids a review
Advances in Colloid and Interface Science, 2013Co-Authors: Cunlu Zhao, Chun YangAbstract:Abstract This work presents a comprehensive review of Electrokinetics pertaining to non-Newtonian fluids. The topic covers a broad range of non-Newtonian effects in Electrokinetics, including electroosmosis of non-Newtonian fluids, electrophoresis of particles in non-Newtonian fluids, streaming potential effect of non-Newtonian fluids and other related non-Newtonian effects in Electrokinetics. Generally, the coupling between non-Newtonian hydrodynamics and electrostatics not only complicates the Electrokinetics but also causes the fluid/particle velocity to be nonlinearly dependent on the strength of external electric field and/or the zeta potential. Shear-thinning nature of liquids tends to enhance electrokinetic phenomena, while shear-thickening nature of liquids leads to the reduction of electrokinetic effects. In addition, directions for the future studies are suggested and several theoretical issues in non-Newtonian Electrokinetics are highlighted.
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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.
Jérôme F. L. Duval - One of the best experts on this subject based on the ideXlab platform.
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Electrokinetics of soft polymeric interphases with layered distribution of anionic and cationic charges
Current Opinion in Colloid and Interface Science, 2016Co-Authors: Jérôme F. L. Duval, Carsten Werner, Ralf ZimmermannAbstract:Soft surface coatings attract increasing attention due to the versatile options they provide in numerous applications e.g. in the flourishing nanomedicine and nanobiotechnology areas. Optimisation of the performance of such ion- and solvent-permeable polyelectrolytic materials requires a detailed understanding of their electrostatic properties. This task is rendered difficult by the inherent non-uniform distribution of their structural charges. In this article, we review recent advances made in the measurement and theory of the Electrokinetics (electrophoresis/streaming current) of soft surface coatings that carry spatially-separated cationic and anionic charges. Examples of such charge-stratified systems are polyelectrolyte-coated particles, polyelectrolyte multilayers, particles with zwitterionic interfacial functionality, microbial cells or hard-soft composite interfaces. It is shown here that the electrokinetic features of such colloidal systems are remarkably different from those of their counterparts with homogeneously distributed cationic and anionic charges. In particular, the interplay between electrostatic and hydrodynamic flow fields developed under electrokinetic conditions in the bulk and interfacial compartments of charge-stratified colloids/films are shown to induce a reversal of their electrokinetic response (electrophoretic mobility/streaming current) that depends on the concentration of monovalent electrolyte in solution. The prerequisites for occurrence of such spectacular behaviour are theoretically identified in terms of the Debye length, the spatial length scales defining charge layering, and the typical length for flow penetration within the colloids/films. Electrophoresis and streaming current results recently reported for poly(amidoamine) carboxylated nanodendrimers, natural rubber colloids and poly(ethyleneimine)-supported lipid bilayers are further discussed to illustrate the generic electrokinetic properties of soft interfaces defined by a given stratification of their anionic and cationic structural charges.
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impact of the virus purification protocol on aggregation and Electrokinetics of ms2 phages and corresponding virus like particles
Physical Chemistry Chemical Physics, 2013Co-Authors: Jérôme F. L. Duval, C Dika, Christophe Gantzer, A PerrinAbstract:Previous experimental and theoretical studies have established that electrokinetic and aggregation properties of soft MS2 phages are not only governed by the physico-chemical features of their proteinaceous outer surface but are also significantly impacted by those of their inner RNA component (Dika et al. Appl. Environ. Microbiol., 2011, 14, 4939–4948). These conclusions contradict the recent findings of Nguyen et al. (Soft Matter, 2011, 7, 10449–10456) who reported identical electrokinetic and aggregation characteristics for MS2 and corresponding virus like particles (VLPs) that lack the internal RNA component. We demonstrate here that this contradiction originates from the different purification methods adopted prior to measurements. More generally, we show that stability and electrohydrodynamics of viruses differ according to purification by (i) dialysis, (ii) isopycnic centrifugation in the cesium chloride gradient, and (iii) precipitation using polyethylene glycol (PEG). Methods (i) and (iii) lead to aggregation of MS2 phages at pH ≤ 4 and pH ≤ 6 in 1–100 mM NaNO3 solutions, respectively, while under such conditions aggregation is not observed for MS2 and VLP suspensions prepared according to (ii). In addition, VLPs prepared following methods (i) and (iii) aggregate only at the isoelectric point (pH ∼ 3–4) in 1 mM NaNO3 solution. Electrophoretic mobility data of stable MS2 and VLP particles were further examined using a recent formalism for Electrokinetics of soft multilayered colloids. The analysis qualitatively shows how the purification protocol may affect either the outer particle surface properties and/or the inner particle content. Finally, the non-DLVO aggregation behavior of MS2 and VLPs purified via the above protocols is discussed in terms of the possible change in corresponding interparticular interactions.
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interrelations between charging structure and Electrokinetics of nanometric polyelectrolyte films
Journal of Colloid and Interface Science, 2011Co-Authors: Jérôme F. L. Duval, Carsten Werner, David Kuttner, Mirko Nitschke, Ralf ZimmermannAbstract:Abstract Streaming current, surface conductivity and swelling data of poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI) thin films are analyzed on the basis of the theory for diffuse soft interfaces (J.F.L. Duval, R. Zimmermann, A.L. Cordeiro, N. Rein, C. Werner, Langmuir 25 (2009) 10691). Focus is put on ways to unravel the electroosmotic and migration contributions of the measured surface conductivity, which is crucial for appropriate electrokinetic analysis of films carrying high densities of dissociable groups. Results demonstrate that the osmotically-driven swelling of the PAA films with increasing pH is accompanied by an increase in diffuseness for the interphasial polymer segment density distribution. This heterogeneity is particularly marked at low ionic strength with a non-monotonous dependence of the streaming current on pH and the presence of a maximum at pH ∼ 6.5. The analysis of the PEI films evidences heterogeneous swelling with lowering pH, i.e. upon protonation of the amine groups. The characteristic decay length in the interphasial PEI segment density distribution is found to be nearly independent of the pH, which is in line with the moderate swelling determined by ellipsometry. A critical discussion is given on the strengths and limitations of Electrokinetics/surface conductivity for quantifying the coupled electrohydrodynamic and structural properties of moderately to highly swollen polyelectrolyte thin films.
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impact of internal rna on aggregation and Electrokinetics of viruses comparison between ms2 phage and corresponding virus like particles
Applied and Environmental Microbiology, 2011Co-Authors: C Dika, Jérôme F. L. Duval, H M Lychatain, Christophe Merlin, Christophe GantzerAbstract:: We compare for the first time the electrokinetic and aggregation properties of MS2 phage (pH 2.5 to 7, 1 to 100 mM NaNO(3) electrolyte concentration) with those of the corresponding virus-like particles (VLPs), which lack entirely the inner viral RNA component. In line with our previous work (J. Langlet, F. Gaboriaud, C. Gantzer, and J. F. L. Duval, Biophys. J. 94:3293-3312, 2008), it is found that modifying the content of RNA within the virus leads to very distinct electrohydrodynamic and aggregation profiles for MS2 and MS2 VLPs. Under the given pH and concentration conditions, MS2 VLPs exhibit electrophoretic mobility larger in magnitude than that of MS2, and both have similar isoelectric point (IEP) values (∼4). The electrokinetic results reflect a greater permeability of MS2 VLPs to electroosmotic flow, developed within/around these soft particles during their migration under the action of the applied electrical field. Results also support the presence of some remaining negatively charged component within the VLPs. In addition, MS2 phage systematically forms aggregates at pH values below the IEP, regardless of the magnitude of the solution ionic strength, whereas MS2 VLPs aggregate under the strict condition where the pH is relatively equal to the IEP at sufficiently low salt concentrations (<10 mM). It is argued that the stability of VLPs against aggregation and the differences between Electrokinetics of MS2 and corresponding VLPs conform to recently developed formalisms for the stability and electrohydrodynamics of soft multilayered particles. The differences between the surface properties of these two kinds of particles reported here suggest that VLPs may not be appropriate for predicting the behavior of pathogenic viruses in aqueous media.
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Electrokinetics of diffuse soft interfaces iv analysis of streaming current measurements at thermoresponsive thin films
Langmuir, 2009Co-Authors: Jérôme F. L. Duval, Ralf Zimmermann, Ana L Cordeiro, Nelly Rein, Carsten WernerAbstract:Streaming current measurements were performed on poly(N-isopropylacrylamide)-co-N-(1-phenylethyl) acrylamide [P(NIPAAm-co-PEAAm)] thermoresponsive thin films above and below the transition temperature of the polymer (i.e., at 22 and 4 °C, respectively). Electrokinetic measurements (ionic strength 0.01−10 mM KCl, pH 2.5−9.5 in 1 mM KCl) revealed that the charging of the polymer/aqueous solution interface is determined by unsymmetrical adsorption of hydroxide and hydronium ions onto the Teflon AF substrate that supports the hydrogel film. The magnitude of the streaming current significantly decreased with decreasing temperature, that is, when the hydrogel was swelling. The pH- and ionic strength-dependent data for unswollen and swollen films were interpreted on the basis of the here-reported general theory for the Electrokinetics of diffuse soft gel layers. The formalism based on the Debye−Brinkman equation for hydrodynamics and the nonlinear Poisson−Boltzmann equation for electrostatics extends previous th...
Alexandre Persat - One of the best experts on this subject based on the ideXlab platform.
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basic principles of electrolyte chemistry for microfluidic Electrokinetics part i acid base equilibria and ph buffers
Lab on a Chip, 2009Co-Authors: Alexandre Persat, Robert D Chambers, Juan G SantiagoAbstract:We review fundamental and applied acid–base equilibrium chemistry useful to microfluidic Electrokinetics. We present elements of acid–base equilibrium reactions and derive rules for pH calculation for simple buffers. We also present a general formulation to calculate pH of more complex, arbitrary mixtures of electrolytes, and discuss the effects of ionic strength and temperature on pH calculation. More practically, we offer advice on buffer preparation and on buffer reporting. We also discuss “real world” buffers and likely contamination sources. In particular, we discuss the effects of atmospheric carbon dioxide on buffer systems, namely, the increase in ionic strength and acidification of typical electrokinetic device buffers. In Part II of this two-paper series, we discuss the coupling of acid–base equilibria with electrolyte dynamics and electrochemistry in typical microfluidic electrokinetic systems.
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basic principles of electrolyte chemistry for microfluidic Electrokinetics part ii coupling between ion mobility electrolysis and acid base equilibria
Lab on a Chip, 2009Co-Authors: Alexandre Persat, Matthew E Suss, Juan G SantiagoAbstract:We present elements of electrolyte dynamics and electrochemistry relevant to microfluidic Electrokinetics experiments. In Part I of this two-paper series, we presented a review and introduction to the fundamentals of acid–base chemistry. Here, we first summarize the coupling between acid–base equilibrium chemistry and electrophoretic mobilities of electrolytes, at both infinite and finite dilution. We then discuss the effects of electrode reactions on microfluidic electrokinetic experiments and derive a model for pH changes in microchip reservoirs during typical direct-current electrokinetic experiments. We present a model for the potential drop in typical microchip electrophoresis device. The latter includes finite element simulation to estimate the relative effects of channel and reservoir dimensions. Finally, we summarize effects of electrode and electrolyte characteristics on potential drop in microfluidic devices. As a whole, the discussions highlight the importance of the coupling between electromigration and electrophoresis, acid–base equilibria, and electrochemical reactions.