Nanofluidics: a Pedagogical Introduction Simon Gravelle
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Polyelectrolyte Assisted Charge Titration Spectrometry: Applications to Latex and Oxide Nanoparticles
Polyelectrolyte assisted charge titration spectrometry: applications to latex and oxide nanoparticles F. Mousseau1*, L. Vitorazi1, L. Herrmann1, S. Mornet2 and J.-F. Berret1* 1Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris, France. 2Institut de Chimie de la Matière Condensée de Bordeaux, UPR CNRS 9048, Université Bordeaux 1, 87 Avenue du Docteur A. Schweitzer, Pessac cedex F-33608, France. Abstract: The electrostatic charge density of particles is of paramount importance for the control of the dispersion stability. Conventional methods use potentiometric, conductometric or turbidity titration but require large amount of samples. Here we report a simple and cost-effective method called polyelectrolyte assisted charge titration spectrometry or PACTS. The technique takes advantage of the propensity of oppositely charged polymers and particles to assemble upon mixing, leading to aggregation or phase separation. The mixed dispersions exhibit a maximum in light scattering as a function of the volumetric ratio �, and the peak position �!"# is linked to the particle charge density according to � ~ �!�!"# where �! is the particle diameter. The PACTS is successfully applied to organic latex, aluminum and silicon oxide particles of positive or negative charge using poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). The protocol is also optimized with respect to important parameters such as pH and concentration, and to the polyelectrolyte molecular weight. The advantages of the PACTS technique are that it requires minute amounts of sample and that it is suitable to a broad variety of charged nano-objects. Keywords: charge density – nanoparticles - light scattering – polyelectrolyte complex Corresponding authors: [email protected] [email protected] To appear in Journal of Colloid and Interface Science leading to their condensation and to the formation of the electrical double layer [1]. -
Influence of Polyelectrolyte Multilayer Properties on Bacterial Adhesion
polymers Article Influence of Polyelectrolyte Multilayer Properties on Bacterial Adhesion Capacity Davor Kovaˇcevi´c 1, Rok Pratnekar 2, Karmen GodiˇcTorkar 2, Jasmina Salopek 1, Goran Draži´c 3,4,5, Anže Abram 3,4,5 and Klemen Bohinc 2,* 1 Department of Chemistry, Faculty of Science, University of Zagreb, Zagreb 10000, Croatia; [email protected] (D.K.); [email protected] (J.S.) 2 Faculty of Health Sciences, Ljubljana 1000, Slovenia; [email protected] (R.P.); [email protected] (K.G.T.) 3 Jožef Stefan Institute, Ljubljana 1000, Slovenia; [email protected] (G.D.); [email protected] (A.A.) 4 National Institute of Chemistry, Ljubljana 1000, Slovenia 5 Jožef Stefan International Postgraduate School, Ljubljana 1000, Slovenia * Correspondence: [email protected]; Tel.: +386-1300-1170 Academic Editor: Christine Wandrey Received: 16 August 2016; Accepted: 14 September 2016; Published: 26 September 2016 Abstract: Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were determined by atomic force microscopy and tensiometry. The surface charge was examined by the zeta potential measurements of silica particles covered with polyelectrolyte multilayers, whereby ionic strength and polyelectrolyte concentrations significantly influenced the build-up process. For adhesion experiments, we used the bacterium Pseudomonas aeruginosa. The extent of adhered bacteria on the surface was determined by scanning electron microscopy. The results showed that the extent of adhered bacteria mostly depends on the type of terminating polyelectrolyte layer, since relatively low differences in surface roughness and hydrophobicity were obtained. -
Microfluidics
MICROFLUIDICS Sandip Ghosal Department of Mechanical Engineering, Northwestern University 2145 Sheridan Road, Evanston, IL 60208 1 Article Outline Glossary 1. Definition of the Subject and its Importance. 2. Introduction 3. Physics of Microfluidics 4. Future Directions 5. Bibliography GLOSSARY 1. Reynolds number: A characteristic dimensionless number that determines the nature of fluid flow in a given set up. 2. Stokes approximation: A simplifying approximation often made in fluid mechanics where the terms arising due to the inertia of fluid elements is neglected. This is justified if the Reynolds number is small, a situation that arises for example in the slow flow of viscous liquids; an example is pouring honey from a jar. 3. Ion mobility: Velocity acquired by an ion per unit applied force. 4. Electrophoretic mobility: Velocity acquired by an ion per unit applied electric field. 5. Zeta-potential: The electric potential at the interface of an electrolyte and substrate due to the presence of interfacial charge. Usually indicated by the Greek letter zeta (ζ). 1 6. Debye layer: A thin layer of ions next to charged interfaces (predominantly of the opposite sign to the interfacial charge) due to a balance between electrostatic attraction and random thermal fluctuations. 7. Debye Length: A measure of the thickness of the Debye layer. 8. Debye-H¨uckel approximation: The process of linearizing the equation for the electric potential; valid if the potential energy of ions is small compared to their average kinetic energy due to thermal motion. 9. Electric Double Layer (EDL): The Debye layer together with the set of fixed charges on the substrate constitute an EDL. -
UNIVERSITY of SOUTH CAROLINA EMCH 792C Micro/Nanofluidics And
UNIVERSITY OF SOUTH CAROLINA EMCH 792C Micro/nanofluidics and Lab-on-a-Chip Fall 2009 OUTLINE Instructor Prof. Guiren Wang Room A221, 300 Main Street Office hours: Tu 6:00 – 7:00 p.m., Fr 6:00 – 7:00 p.m. Walk-ins are welcome at other times. Tel. 777-8013 (office), e-mail: [email protected] Textbook • Micro- and Nanoscale Fluid Mechanics for Engineers: Transport in Microfluidic Devices By Brian J. Kirby. 2009. References • Tabeling, P. Introduction to Microfluidics, Oxford, 2005. • Probstein, R.F. Physicochemical Hydrodynamics, 2nd Ed., Wiley, 1994 • Bruss, H. Theoretical Microfluidics, Oxford, 2008. • Nguyen, N-T and Wereley, S “Fundamentals and Applications of Microfluidics”, 2nd Edition, Artech House, ISBN: 1580539726 • Berthier J. and Silberzan, P. Microfluidics for Biotechnology. Artech House Publishers. ISBN: 1-58053-961-0. Catalog Course Description EMCH 792C Micro/nanofluidics and Lab-on-a-Chip. (3) Introduction of microlfuidics and applications in life science. Content: Fundamentals and engineering concept: Introduction of basic principle of fluid mechanics, Navier-Stokes equation, non-slip condition, capillary, drop and micro/nanoparticle, electrokinetics; Introduction to microfabrication: soft-lithography, self-assembled monolayers; Microfluidic components and sample preparation: micro- pump, filter, valve, dispenser, mixer, reactor, preconcentrator, separation based on electrokinetics, microactuator and particle manipulator; Experimental measurements: microscopy, fluorescence and laser-induced fluorescence, measurement of flow velocity, temperature and concentration; Applications in chemistry and life science: sensors for pressure, velocity, concentration, temperature, biosensor in environmental monitoring and biodefence, clinical diagnostics, drug discovery and delivery, etc. Course Objectives: At the conclusion of this course, students will be able to: 1. Understanding some advanced fluid mechanics relevant to micro scale device. -
Surface Polarization Effects in Confined Polyelectrolyte Solutions
Surface polarization effects in confined polyelectrolyte solutions Debarshee Bagchia , Trung Dac Nguyenb , and Monica Olvera de la Cruza,b,c,1 aDepartment of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; bDepartment of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208; and cDepartment of Physics and Astronomy, Northwestern University, Evanston, IL 60208 Contributed by Monica Olvera de la Cruz, June 24, 2020 (sent for review April 21, 2020; reviewed by Rene Messina and Jian Qin) Understanding nanoscale interactions at the interface between ary conditions (18, 19). However, for many biological settings two media with different dielectric constants is crucial for con- as well as in supercapacitor applications, molecular electrolytes trolling many environmental and biological processes, and for confined by dielectric materials, such as graphene, are of interest. improving the efficiency of energy storage devices. In this Recent studies on dielectric confinement of polyelectrolyte by a contributed paper, we show that polarization effects due to spherical cavity showed that dielectric mismatch leads to unex- such dielectric mismatch remarkably influence the double-layer pected symmetry-breaking conformations, as the surface charge structure of a polyelectrolyte solution confined between two density increases (20). The focus of the present study is the col- charged surfaces. Surprisingly, the electrostatic potential across lective effects of spatial confinement by two parallel surfaces -
Semester II, 2015-16 Department of Physics, IIT Kanpur PHY103A: Lecture # 5 Anand Kumar
Semester II, 2017-18 Department of Physics, IIT Kanpur PHY103A: Lecture # 8 (Text Book: Intro to Electrodynamics by Griffiths, 3rd Ed.) Anand Kumar Jha 19-Jan-2018 Summary of Lecture # 7: • Electrostatic Boundary Conditions E E = Electric Field: = above below E − E = 00 above− below � 0 above − below Electric Potential: V V = 0 above − below • Basic Properties of Conductors (1) The electric field = 0 inside a conductor, always. = 0 = = 0 (2) The charge density inside a conductor. This is because . (3) Any net charge resides on the surface. Why? To minimize the energy. 0 ⋅ (4) A conductor is an equipotential. (5) is perpendicular to the surface, just outside the conductor. 2 Summary of Lecture # 7: Prob. 2.36 (Griffiths, 3rd Ed. ): - Surface charge ? = = − 2 - Surface charge ? 4 + - Surface charge ? = − 2 4 1 2 - ( ) ? = 4 out 2 1 0 � - ( ) ? = 4 out 2 10 �+ - ( ) ? =4 out out 2 � - Force on ? 0 40 - Force on ? 0 3 Summary of Lecture # 7: Prob. 2.36 (Griffiths, 3rd Ed. ): - Surface charge ? = Same ª = − 2 Same - Surface charge ? 4 ª + - Surface charge ? = − 2 Changes � 4 1 2 = - ( ) ? 4 Same ª out 2 1 0 � = 4 - ( ) ? Same ª out 2 � 10 + Changes � - ( ) ? =4 out out 2 - Force on ? 0 0 � 4 Same ª Bring in a third - Force on ? 0 Same ª charge 4 Surface Charge and the Force on a Conductor: What is the electrostatic force on the patch? Force per unit area on the patch is: = (? ) = other = + , above other patch above = + 2 other 0 � = + , below other patch below 1 = = + 2 2 other − � other above below 0 But, inside a metal, = , so = 0 below = = + = 2 2 other � above other � � 5 0 0 0 Surface Charge and the Force on a Conductor: What is the electrostatic force on the patch? Force per unit area on the patch is: = (? ) = other = = 2 other � above � Force per unit0 area on the patch is: 0 = = 2 2 other � Force per unit area is pressure.0 So, the electrostatic pressure is: = = 2 2 20 2 6 0 Capacitor: Two conductors with charge and . -
Ion Current Rectification in Extra-Long Nanofunnels
applied sciences Article Ion Current Rectification in Extra-Long Nanofunnels Diego Repetto, Elena Angeli * , Denise Pezzuoli, Patrizia Guida, Giuseppe Firpo and Luca Repetto Department of Physics, University of Genoa, via Dodecaneso 33, 16146 Genoa, Italy; [email protected] (D.R.); [email protected] (D.P.); [email protected] (P.G.); giuseppe.fi[email protected] (G.F.); [email protected] (L.R.) * Correspondence: [email protected] Received: 29 April 2020; Accepted: 25 May 2020; Published: 28 May 2020 Abstract: Nanofluidic systems offer new functionalities for the development of high sensitivity biosensors, but many of the interesting electrokinetic phenomena taking place inside or in the proximity of nanostructures are still not fully characterized. Here, to better understand the accumulation phenomena observed in fluidic systems with asymmetric nanostructures, we study the distribution of the ion concentration inside a long (more than 90 µm) micrometric funnel terminating with a nanochannel. We show numerical simulations, based on the finite element method, and analyze how the ion distribution changes depending on the average concentration of the working solutions. We also report on the effect of surface charge on the ion distribution inside a long funnel and analyze how the phenomena of ion current rectification depend on the applied voltage and on the working solution concentration. Our results can be used in the design and implementation of high-performance concentrators, which, if combined with high sensitivity detectors, could drive the development of a new class of miniaturized biosensors characterized by an improved sensitivity. Keywords: nanofunnel; FEM simulation; ionic current rectification; micro-nano structure interface 1. -
Screened Electrostatic Interaction of Charged Colloidal Particles in Nonpolar Liquids Carlos Esteban Espinosa
Screened Electrostatic Interaction of Charged Colloidal Particles in Nonpolar Liquids A Thesis Presented to The Academic Faculty by Carlos Esteban Espinosa In Partial Fulfillment of the Requirements for the Degree Master of Science in Chemical Engineering School of Chemical & Biomolecular Engineering Georgia Institute of Technology August 2010 Screened Electrostatic Interaction of Charged Colloidal Particles in Nonpolar Liquids Approved by: Dr. Sven H. Behrens, Adviser School of Chemical & Biomolecular Engineering Georgia Institute of Technology Dr. Victor Breedveld School of Chemical & Biomolecular Engineering Georgia Institute of Technology Dr. Carson Meredith School of Chemical & Biomolecular Engineering Georgia Institute of Technology Date Approved: 12 May 2010 ACKNOWLEDGEMENTS First, I would like to thank my adviser, Dr. Sven Behrens. His support and orienta- tion was essential throughout the course of this work. I would like to thank all members of the Behrens group that have made all the difference. Dr. Virendra, a great friend and a fantastic office mate who gave me im- portant feedback and guidance. To Qiong and Adriana who helped me throughout. To Hongzhi Wang, a great office mate. I would also like to thank Dr. Victor Breedveld and Dr. Carson Meredith for being part of my committee. Finally I would like to thank those fellow graduate students in the Chemical Engineering Department at Georgia Tech whose friendship I am grateful for. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS .......................... iii LIST OF TABLES ............................... vi LIST OF FIGURES .............................. vii SUMMARY .................................... x I INTRODUCTION ............................. 1 II BACKGROUND .............................. 4 2.1 Electrostatics in nonpolar fluids . .4 2.1.1 Charge formation in nonpolar fluids . .4 2.1.2 Charge formation in nonpolar oils with ionic surfactants . -
Beryllium Desorption from Minerals and Organic Ligands Over Time
Chemical Geology 439 (2016) 52–58 Contents lists available at ScienceDirect Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo Beryllium desorption from minerals and organic ligands over time Vanessa Boschi ⁎,JaneK.Willenbring Department of Earth and Environmental Science, University of Pennsylvania, 251 Hayden Hall, 240 South 33rd Street, Philadelphia, PA 19104, USA article info abstract Article history: Beryllium isotopes sorbed to sediments have provided useful tools in the field of geochronology and geomor- Received 13 April 2016 phology over the last few decades. The use of beryllium isotopes relies on the premise that beryllium sorbed to Received in revised form 3 June 2016 sediments is unaltered over large timescales. Changes in the environmental chemistry, either in-situ or en Accepted 10 June 2016 route from soil to fluvial system, to the ocean, can cause beryllium desorption and may preclude some beryllium Available online 11 June 2016 isotopic applications. Keywords: Four mechanisms were tested to determine the relative desorption potential of beryllium including a reduction Beryllium in pH, an increase in ionic strength (NaCl) and complexation by soluble organic (malonic acid) and inorganic spe- Desorption cies (NaF). To assess the relative effect of each mechanism on beryllium desorption from both organic and min- Minerals eral fractions, we prepared separate solutions of beryllium bound to minerals and organic compounds and Organic ligands measured beryllium concentrations in solution before and after each chemical perturbation. We conclude a re- Inner and outer sphere complexation duction in pH resulted in the greatest amount of desorption among the four treatments, removing 97% and 75% of sorbed beryllium from illite and montmorillonite, respectively, and none from the organic ligands tested. -
6.007 Lecture 5: Electrostatics (Gauss's Law and Boundary
Electrostatics (Free Space With Charges & Conductors) Reading - Shen and Kong – Ch. 9 Outline Maxwell’s Equations (In Free Space) Gauss’ Law & Faraday’s Law Applications of Gauss’ Law Electrostatic Boundary Conditions Electrostatic Energy Storage 1 Maxwell’s Equations (in Free Space with Electric Charges present) DIFFERENTIAL FORM INTEGRAL FORM E-Gauss: Faraday: H-Gauss: Ampere: Static arise when , and Maxwell’s Equations split into decoupled electrostatic and magnetostatic eqns. Electro-quasistatic and magneto-quasitatic systems arise when one (but not both) time derivative becomes important. Note that the Differential and Integral forms of Maxwell’s Equations are related through ’ ’ Stoke s Theorem and2 Gauss Theorem Charges and Currents Charge conservation and KCL for ideal nodes There can be a nonzero charge density in the absence of a current density . There can be a nonzero current density in the absence of a charge density . 3 Gauss’ Law Flux of through closed surface S = net charge inside V 4 Point Charge Example Apply Gauss’ Law in integral form making use of symmetry to find • Assume that the image charge is uniformly distributed at . Why is this important ? • Symmetry 5 Gauss’ Law Tells Us … … the electric charge can reside only on the surface of the conductor. [If charge was present inside a conductor, we can draw a Gaussian surface around that charge and the electric field in vicinity of that charge would be non-zero ! A non-zero field implies current flow through the conductor, which will transport the charge to the surface.] … there is no charge at all on the inner surface of a hollow conductor. -
The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration Alexander M. Smith*,a, Alpha A. Lee*,b and Susan Perkin*,a aDepartment of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, U.K. bSchool of EnGineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA Corresponding author emails: [email protected] [email protected] [email protected] 1 ABSTRACT According to classical electrolyte theories interactions in dilute (low ion density) electrolytes decay exponentially with distance, with the Debye screeninG lenGth the characteristic length-scale. This decay length decreases monotonically with increasing ion concentration, due to effective screening of charges over short distances. Thus within the Debye model no long-range forces are expected in concentrated electrolytes. Here we reveal, using experimental detection of the interaction between two planar charged surfaces across a wide range of electrolytes, that beyond the dilute (Debye- Hückel) regime the screening length increases with increasing concentration. The screening lengths for all electrolytes studied – including aqueous NaCl solutions, ionic liquids diluted with propylene carbonate, and pure ionic liquids – collapse onto a single curve when scaled by the dielectric constant. This non-monotonic variation of the screening length with concentration, and its generality across ionic liquids and aqueous salt solutions, demonstrates an important characteristic of concentrated electrolytes of substantial relevance from biology to energy storage. TOC Image: 2 Electrolytes are ubiquitous in nature and in technology: from the interior of cells to the oceans, from supercapacitors to nanoparticle dispersions, electrolytes act as both solvent and ion conduction medium. -
Electrophoresis of Charged Macromolecules
Electrophoresis of Charged Macromolecules Christian Holm Institut für Computerphysik, Universität Stuttgart Stuttgart, Germany 1! Charge stabilized Colloids! The analytical description of charged colloidal suspensions is problematic:! n " Long ranged interactions: electrostatics/ hydrodynamics! n " Inhomogeneous/asymmetrical systems! n " Many-body interactions! Alternative! : the relevant microscopic degrees of freedom are simulated! via Molecular Dynamics! ●Explicit" particles (ions) with charges ε ●Implicit" solvent approach, but hydrodynamic interactions of the solvent are included via a Lattice-Boltzmann algorithm Test of LB implementation for Poiseuille! Simulation box of size 80x40x10. Velocity profile for a Poiseuille flow in a channel, which is tilted by 45◦ relative to the Lattice-Boltzmann node mesh. Computed using ESPResSo. Profile of the absolute fluid velocity of the Poiseuille flow in the 45◦ tilted channel. Red crosses represent simulation data, the blue line is the theoretical result and the dashed blue line represents the theoretical result, using the channel width as a fit parameter 3! EOF in a Slit Pore! Simulation results for a water system. Solid lines denote simulation results, the dotted lines show the analytical results for comparison. Red stands for ion density in particles per nm3, blue stands for the fluid velocity in x-direction, green denotes the particle velocity. All quantities in simulation units. 4! Colloidal Electrophoresis! local force balance FE = FDrag leads to stationary state ν FE F = Z E − Zeff