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 Time dependent Active Microrheology in Dilute Colloidal Suspensions written by Sebastian Leitmann and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Rheology of Attractive Suspensions written by Derek Eusean Huang and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Complex fluids form a broad class of materials, examples of which include foodstuffs, personal care products, biological fluids, industrial compounds, and geological materials. Detailed knowledge of their flow behavior is therefore key to understanding and predicting natural phenomena or developing new materials. In the past century, major advances in both experimental and theoretical methods have enabled greater understanding of the connection between the microscopic physical structure of complex fluids and their material response. Traditional rheology involves imposing deformation on a macroscopic sample of fluid and measuring the stress response. However, an increasing need to interrogate microscopically-small fluid samples, and a heightened interest in the colloid-level physics of biology, have motivated the development of techniques to interrogate microliter-size samples and resolve micron-length heterogeneities. One of these experimental techniques is active microrheology, where a microscopically small probe particle is driven through the material of interest. Constitutive relations between the force required to drive the probe and the speed with which it moves allow one to infer the effective viscosity of the material, and more recent expansions of the theory of active microrheology allow the direct measurement of suspension stress by monitoring the mean and fluctuating motion of the probe. Theoretical models that connect probe motion to material and flow properties have enjoyed great expansion in the last decade for the study of complex fluids of particles interacting hydrodynamically, or with repulsive forces. However, many systems of interest, including biological cells, comprise colloidal suspensions that experience attractive forces not previously represented in theoretical models. This work presents a theoretical study of the impact of attractive forces on the microstructure, microviscosity, and nonequilibrium osmotic pressure of colloidal suspensions as measured by active microrheology. In active microrheology, the probe distorts the surrounding microstructure from its equilibrium configuration. The degree of this distortion is set by the strength of external forcing relative to entropic restoring forces; interparticle attractions and repulsions also influence this evolution. Although the effects of repulsions are well-studied in prior literature, a theoretical understanding of attraction-induced effects on nonequilibrium rheology is lacking. To examine how this interplay between different microscopic forces influences rheology, we formulate a Smoluchowski equation governing pair configuration as it evolves with flow strength, interparticle attractions, and hydrodynamic interactions. We determine its solution and compute microviscosity and nonequilibrium osmotic pressure from the structure via statistical mechanics. When the probe is subject to external forcing, attractions speed upstream probe-bath encounters and slow downstream detachment, transferring particle density downstream. This sets both the strength and direction of dipolar disturbance under weak forcing and the boundary-layer and wake structure under strong forcing. These attraction-induced structural changes affect rheology: both attraction-thinning and attraction-thickening are observed in the weak-forcing limit, while sufficiently strong forcing breaks attractive bonds and leads to flow-thinning or, in the presence of hydrodynamic interactions, flow-thickening. We find that the equilibrium osmotic pressure, described by the second virial coefficient B2, accurately predicts structural and rheological behavior in the weak-forcing limit regardless of specific attractive potential, but that the secondary length scale that arises under strong forcing precludes potential-agnostic observations far from equilibrium. The structural transitions and non-monotonic rheology in active microrheology show that tuning surface stickiness can either enhance or hinder probe motion and provide a means by which proteins or other macromolecules may change their surface chemistry to alter the viscosity of the surrounding medium, either speeding or slowing their own motion. Attractive forces are known to reduce the equilibrium osmotic pressure; as the second virial coefficient becomes more strongly negative, it is possible for phase separation to occur. This behavior changes away from equilibrium, where we find that the flow-induced nonequilibrium osmotic pressure reaches a minimum at a critical value of B2 before increasing with attraction strength. Hydrodynamic interactions suppress the nonequilibrium osmotic pressure and, at certain attraction strengths, can give rise to a flow-induced reduction in osmotic pressure below its equilibrium value. This denotes a flow-induced destabilization of attractive suspensions that may lead to phase separation in more concentrated systems, suggesting that self-assembly of active particles in biological suspensions may be driven by both attractive forces and hydrodynamic interactions
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 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 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 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 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 Colloidal Suspension Rheology written by Norman J. Wagner and published by . This book was released on 2011 with total page 480 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 pharmaceuticals. 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.
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"--
Download or read book Theory and Applications of Colloidal Suspension Rheology written by Norman J. Wagner and published by Cambridge University Press. This book was released on 2021-04-15 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Essential text on the practical application and theory of colloidal suspension rheology, written by an international coalition of experts.
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 Colloidal Suspension Rheology Suspensions in viscoelastic media 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"--
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 Effect of Particle Shape on the Structure and Rheology of Colloidal Suspensions and Gels written by Ali Mohraz and published by . This book was released on 2004 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
