Download or read book Active and Nonlinear Microrheology of Dense Colloidal Suspensions written by Christian Josef Harrer and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nonlinear Microrheology of Dense Colloidal Suspensions written by Igor Gazuz and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Microrheology of Colloidal Suspensions written by Indira Sriram and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Typically, rheology is measured using bulk rheological techniques, which give information about the macroscopic properties of the fluid, such as viscosity, and elastic modulus. However, the recent advances in sensitive microscopic and optical techniques have led to the emergence of a new field, known as microrheology. Microrheological measurements are capable of resolving forces on the order of piconewtons, and can obtain very localized structural information in the test fluid. All microrheological techniques utilize embedded probe particles to determine the surrounding fluid properties. The most common form of microrheology is "passive" microrheology, wherein the probe particles execute purely Brownian or thermal motion. Alternatively, in "active" microrheology, probe particles are manipulated using an external source of force, such as laser tweezers or magnetic tweezers. Both techniques present specific advantages. Passive microrheology has been widely adopted because the design and implementation of experiments is relatively straightforward. However, since passive microrheology is constrained to rely on purely thermal motion, the recovered fluid behavior is always in a linear response regime. The goal of the present work is to adapt active microrheology to measure non-linear fluid properties such as shear thinning, and to determine the conditions where such measurements agree with bulk rheology. We begin by developing a small amplitude, oscillatory active microrheological technique, where a single probe particle is trapped and oscillated in a suspension of small bath particles, whose diameter that is approximately twenty times smaller than that of the probe diameter. The suspension microviscosity is recovered across a frequency range of 5-1000 Hz, and applied amplitudes which are approximately 10% of the probe diameter. We find that the suspension exhibits thinning behavior with increasing frequency. In addition, we obtain quantitative agreement between our microrheological measurements, drag microrheology measurements, and bulk rheology, suggesting that this technique is capable of recovering bulk viscosity values. Finally, we compare our results to a new theoretical model that accounts for the three sources of stress in active microrheological measurements of colloidal suspensions: (i) direct interactions between the probe and bath particles (ii) indirect interactions between bath particles, and (iii) Einstein stresses that arise from the particles' inability to shear in the same manner as the surrounding fluid. Notably, while indirect interactions and Einstein stresses are present in macroscopic techniques, direct interactions have no macroscopic analog. Therefore, if indirect interactions dominate in the measurements, the bulk suspension viscosity can be recovered. We find that indirect interactions dominate in the limit that the probe particle is far larger than the surrounding bath particles, and therefore determine both experimentally and analytically that our measurements recover the bulk suspension viscosity. Next, we analyze single probe drag measurements in a suspension of fluorescently labeled bath particles. We recover the suspension microviscosity, and directly correlate this to the microstructural deformation in the bath suspension. We find that the suspension exhibits thinning behavior as the velocity of the probe increases. In addition, the measured microviscosity is found to be in good agreement with recent computational studies in the "direct" collision limit, which is a measurement artifact when considering the bulk, non-linear response in a suspension. In addition, we find some departure between our experimental results, and recently performed theoretical studies, which we attribute to the presence of hydrodynamic interactions in our system. We further characterize the anisotropic, non-linear structures formed in the direct probe limit by performing two probe experiments in a colloidal suspension. We hypothesize that these structures could potentially lead to interprobe interactions. First, we hold two particles such that the line joining their centers is normal to the flow direction, and then conduct measurements as a function of probe velocity and interparticle separation. Both the drag force and microstructural deformation surrounding the particles are recovered. Intriguingly, we find that the microstructure induces a slight attraction between the probe particles, particularly at close separations, constituting a "non-equilibrium" depletion interaction. We then conduct two point measurements with the line joining the particles aligned parallel to the flow direction, and reexamine the forces on the probes, and the microstructural effects in the bath suspension. We find that the drag force experienced by both particles is the same, despite their orientation to the flow direction. In addition, we find several microstructural effects that differ from both the single probe and perpendicular case.

Download or read book Linear and Non linear Microrheology of Colloidal Suspensions written by Eric M. Furst and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloidal Suspension Rheology written by Jan Mewis and published by Cambridge University Press. This book was released on 2012 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented in an accessible and introductory manner, this is the first book devoted to the comprehensive study of colloidal suspensions.

Download or read book Nonlinear Response of Dense Colloidal Suspensions Under Oscillatory Shear written by Joseph M. Brader and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microrheology written by Eric M. Furst and published by Oxford University Press. This book was released on 2017 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rheology is the study of the flow of matter. It is an important and active field of research that spans numerous disciplines and technological applications. The aim of this work is to provide an introduction to the theory and practice of microrheology, a relatively new area of rheology.

Download or read book Suspensions of Colloidal Particles and Aggregates written by Frank Babick and published by Springer. This book was released on 2016-04-04 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between aggregates. It is illustrated how such knowledge may significantly enhance the characterisation of colloidal suspensions. The final part of the book refers to the information, ideas and concepts already presented in order to address technical aspects of the preparation of colloidal suspensions—in particular the performance of relevant dispersion techniques and the stability of colloidal suspensions.

Download or read book Active and Passive Particle Transport in Dense Colloidal Suspensions written by Igor Gazuz and published by . This book was released on 2008 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Properties of Non equilibrium States written by Matthias Helmut Günter Krüger and published by . This book was released on 2009 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modelling the Behaviour of Dense Colloidal Suspensions of Cuboids written by Luca Tonti and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dense Colloidal Suspensions in Microchannel Flow written by Philipp Kanehl and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloidal Suspension Rheology written by Jan Mewis and published by . This book was released on 2012 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Colloidal suspensions are encountered in a multitude of natural, biological, and industrially relevant products and processes. Understanding what affects the flow behavior, or rheology, of colloid particles, and how these suspensions can be manipulated, is important for successful formulation of products such as paint, polymers, foods, and harmaceuticals. This book is the first devoted to the study of colloidal rheology in all its aspects. With material presented in an introductory manner, and complex mathematical derivations kept to a minimum, the reader will gain a strong grasp of the basic principles of colloid science and rheology. Beginning with purely hydrodynamic effects, the contributions of Brownian motion and interparticle forces are covered, before the reader is guided through specific problem areas such as thixotropy and shear thickening; special classes of colloid suspensions are also treated. An essential guide for academic and industrial researchers, this book is also ideal for graduate course use"--Résumé de l'éditeur.

Download or read book Contact and Macroscopic Aging in Dense Suspensions at the Colloidal Edge written by Francesco Bonacci and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dense colloidal suspensions (or pastes) constitute a broad class of materials found in areas ranging from environmental systems (e.g. silts, clays), to industry (ceramics, drilling muds, slurries), construction (plaster, cements), foodstuff, cosmetics, pharmaceuticals (toothpaste, medical ceramics). Their most remarkable feature is thixotropy: a slow evolution of their mechanical properties when switching from rest to flow (at fixed density, in the absence of drainage). Thus, their viscosity under flow, or their shear modulus and yield stress at rest, depend both on time and strain history. Thixotropy enables these systems to switch reversibly between solid- and liquid-like states with sharply contrasted properties. At rest, it is usually accompanied with aging--slow, non-exponential dynamics at long times. In recent decades, tremendous progress has been made towards understanding the dynamics of so-called "stabilized" suspensions, in which the formation of interparticle adhesive contacts is fully avoided by tuning inter-particle interactions (via double-layer polarization, or polymer depletion effects). Confocal microscopy was instrumental to such progresses, yet may only be applied to transparent, i.e. nearly index matched, systems, hence is limited to systems in which van der Waals forces are absent. Meanwhile, studies of "non-stabilized" suspensions have tended to focus on very dilute systems (i.e. packing fractions at most a few percent) where a structural evolution (the formation of flocs) could be imaged and thus analyzed, e.g., using light scattering techniques. The tremendous success of these studies has created an observational bias as, today, classical works on suspensions only mention structural dynamics as the root cause of thixotopy. But the pastes of civil and environmental engineering, are dense and generally contain significant concentrations of ions; these screen Coulombic repulsion and allow attractive van der Waals forces to bring particles into solid-solid contacts, which are likely to impact macroscopic properties and their evolution by a number of mechanisms. Indeed, it is well-known that, the macroscopic response of non-colloidal granular materials, is affected by contact friction, which is time- dependent. In cements, the formation of hydrate gels between grains, which determines the late-time strength and mechanical properties of solid concrete, was proposed to play a role in thixotropy. In fact, it remains unclear how solid-solid contacts may affect just the elastic modulus of colloidal systems. By designing an optical trap three-point bending test, Pantina and Furst showed that beams of PMMA and polystyrene particles present a finite flexural modulus, which entails that the contacts formed between particles resist rotation. The flexural modulus of polystyrene particle rods was later shown to evolve in time. These two elements lead us to ask whether the evolution of the contact bending stiffness could be responsible for mechanical aging in pastes, without invoking changes in the network structure. This work aims to investigate the potential existence of a link between contact and macroscopic aging, by combining measurements performed at the particle level, through optical-trap three-point bending tests and confocal microscopy, and at the macroscopic scale, through rheometry. To achieve it, we study the aging behavior of model dense colloidal suspensions composed of silica (SiO2) and PMMA particles suspended in divalent electrolyte aqueous solutions, at moderate concentrations. The use of model ionic systems enables us to carefully control a number of parameters expected to affect the rheology of real suspensions in the dense regime, such as the volume fraction, the size and the shape of the particles and the magnitude of the interactions.

Download or read book Transient Dynamics in Dense Colloidal Suspensions Under Shear written by Marco Laurati and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloids in Non equilibrium Dynamical Density Functional Theory of Colloidal Suspensions Under External Forcing written by Urs Zimmermann and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloidal Suspension Rheology Weakly flocculated suspensions written by J. Mewis and published by . This book was released on 2012 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Colloidal suspensions are encountered in a multitude of natural, biological, and industrially relevant products and processes. Understanding what affects the flow behavior, or rheology, of colloid particles, and how these suspensions can be manipulated, is important for successful formulation of products such as paint, polymers, foods, and harmaceuticals. This book is the first devoted to the study of colloidal rheology in all its aspects. With material presented in an introductory manner, and complex mathematical derivations kept to a minimum, the reader will gain a strong grasp of the basic principles of colloid science and rheology. Beginning with purely hydrodynamic effects, the contributions of Brownian motion and interparticle forces are covered, before the reader is guided through specific problem areas such as thixotropy and shear thickening; special classes of colloid suspensions are also treated. An essential guide for academic and industrial researchers, this book is also ideal for graduate course use"--