The aim of this work is to provide an introduction to the theory and practice of microrheology, a relatively new area of rheology.
Author: Eric M. Furst
Publisher: Oxford University Press
This book presents a comprehensive overview of microrheology, emphasizing the underlying theory, practical aspects of its implementation, and current applications to rheological studies in academic and industrial laboratories. The field of microrheology continues to evolve rapidly, and applications are expanding at an accelerating pace. Readers will learn about the key methods and techniques, including important considerations to be made with respect to the materials most amenable to microrheological characterization and pitfalls to avoid in measurements and analysis. Microrheological measurements can be as straightforward as video microscopy recordings of colloidal particle Brownian motion; these simple experiments can yield rich rheological information. Microrheology covers topics ranging from active microrheology using laser or magnetic tweezers to passive microrheology, such as multiple particle tracking and tracer particle microrheology with diffusing wave spectroscopy. Overall, this introduction to microrheology informs those seeking to incorporate these methods into their own research, or simply survey and understand the growing body of microrheology literature. Many sources of archival literature are consolidated into an accessible volume for rheologist and non-specialist alike. The small sample sizes of many microrheology experiments have made it an important method for studying emerging and scarce biological materials, making this characterization method suitable for application in a variety of fields.
1.3 Microrheology Recently , several new techniques , collectively called microrheology [ 11 , 22-25 ) , have been developed to probe , on microscopic
scales , the material properties of systems , ranging from simple polymer
solutions to the ...
I. Scope The general problem of micro - rheology is the prediction of the
macroscopic rheological properties of a material from a detailed description of
the behavior of the elements of which it is composed . In the present chapter the
The aim of this book is to provide a pedagogical introduction to the physics principles governing both the optical tweezers and their application in the field of microrheology of complex materials.
Author: Manlio Tassieri
Publisher: CRC Press
Thanks to the pioneering works of Ashkin and coworkers, optical tweezers (OTs) have become an invaluable tool for myriad studies throughout the natural sciences. Their success relies on the fact that they can be considered as exceptionally sensitive transducers that are able to resolve pN forces and nm displacements, with high temporal resolution, down to μs. Hence their application to study a wide range of biological phenomena such as measuring the compliance of bacterial tails, the forces exerted by a single motor protein, and the mechanical properties of human red blood cells and of individual biological molecules. The number of articles related to them totals to a whopping 58,000 (source Google Scholar)! Microrheology is a branch of rheology, but it works at micrometer length scales and with microliter sample volumes. Therefore, microrheology techniques have been revealed to be very useful tools for all those rheological/mechanical studies where rare or precious materials are employed, such as in biological and biomedical studies. The aim of this book is to provide a pedagogical introduction to the physics principles governing both the optical tweezers and their application in the field of microrheology of complex materials. This is achieved by following a linear path that starts from a narrative introduction of the "nature of light," followed by a rigorous description of the fundamental equations governing the propagation of light through matter. Moreover, some of the many possible instrumental configurations are presented, especially those that better adapt to perform microrheology measurements. In order to better appreciate the microrheological methods with optical tweezers explored in this book, informative introductions to the basic concepts of linear rheology, statistical mechanics, and the most popular microrheology techniques are also given. Furthermore, an enlightening prologue to the general applications of optical tweezers different from rheological purposes is provided at the end of the book.
"The actin cytoskeleton is a key determinant of cell force production, mechanical integrity and structure, and mechanosensation.
Author: Chris Sitaras
"The actin cytoskeleton is a key determinant of cell force production, mechanical integrity and structure, and mechanosensation. An essential yet often overlooked element of the actin cytoskeleton is the crosslinker, alpha-actinin 4 (ACTN4), which in vitro, has been shown to exhibit catch-bond behavior and determine the mechanical relaxation of purified actin networks. ACTN4's role in determining the mechanical properties of the cytoplasm, however, is unclear. Here we use a combination of Passive Microrheology (PMR), Optical Magnetic Twisting Cytometry (OMTC), and Magnetic Tweezers (MTs) to probe the moduli and creep behavior of the cytoplasm in living cells. We use cell-surface adhered of 4.66 μm ferrimagnetic iron oxide particles or 200 nm fluorescent super-paramagnetic particles as probes, and then measure their displacement due to a force regime. The quantified time-dependent displacement of the particles is applied to mathematical models in order to ascertain the viscoelastic properties of the cytoplasm. To evaluate the role of ACTN4, we employ two cell lines: wild type ACTN4, and a mutated variant (K255E), which has previously been shown to exhibit stronger actin binding and has been implicated in kidney pathology. These results present some of the first cytoplasmic creep measurements related to crosslinker binding kinetics and provide insight into the detailed cytoskeleton relaxation responsible for cell mechanics." --
The utility of passive microrheology is apparent by both its rapid and widespread
adoption and the number of new applications it enables , such as high
throughput screening , characterization of the cell cytoplasm , and studies of
Includes abstracts from the Journal of the Society of Rheology, Japan.
This analytical EEI model successfully describes the empirically measured volume-fraction dependent G'p() for microscale emulsions and nanoemulsions without any ad hoc adjustments to the empirically measured and with very few adjustable ...
Author: Ha Seong Kim
Emulsions are an interesting class of soft materials and have a wide range of practical applications in industry and in consumer goods. To design and tailor the mechanical properties of concentrated emulsions at high droplet volume fractions for specific applications and products, it is helpful to have a good quantitative understanding of emulsion rheology. In this dissertation, we describe the improvements that we have made in the quantitative description of the linear plateau elastic shear modulus, G'p, of jammed monodisperse colloidal emulsions that are stabilized by ionic surfactant molecules. We have created an improved analytical model, which accurately describes the G'p of jammed monodisperse micro- and nano-scale emulsions. We incorporate entropic, electrostatic, and interfacial (EEI) contributions into a quasi-equilibrium free energy while retaining key aspects of random jamming of deformable droplets, and we calculate G'p via free energy minimization. This analytical EEI model successfully describes the empirically measured volume-fraction dependent G'p( ) for microscale emulsions and nanoemulsions without any ad hoc adjustments to the empirically measured and with very few adjustable parameters that appear to be universal. In addition, we use this EEI model to identify different -regimes of jamming caused by electrostatic repulsions and droplet interfacial deformations. Using jammed monodisperse emulsions as model system, we have improved diffusing wave spectroscopy (DWS) microrheology analysis for quantifying the rheological properties of dense colloidal systems, particularly G'p( ) of jammed repulsive emulsions. We show that we can correct for collective light scattering effects present in highly scattering concentrated colloidal systems through an empirically determined average structure factor and thereby obtain corrected mean square displacements (MSDs), which lead to accurate values of G'p through the generalized Stokes-Einstein relationship (GSER) of passive microrheology. This advance enables accurate optical microrheology measurements of concentrated emulsions over a wide range of frequencies beyond the capabilities of traditional mechanical rheometers. This approach of correcting DWS MSDs for collective scattering is general and can be applied to other types of highly scattering concentrated colloidal dispersions, not just emulsions. Motivated by advances in DWS microrheology for repulsive emulsions, we perform DWS microrheology studies on depletion-induced attractive emulsions near and below the jamming volume fraction of hard spheres. By adapting the analytical approach developed for repulsive emulsions, we show that in some limits DWS microrheology of attractive emulsions can be extracted and compare accurately with macroscopic mechanical measurements. We reveal systematic features in an excess MSD that is present only for the attractive emulsions, and we attribute this excess MSD to additional dynamics of clusters of droplets that are only loosely attached to the main stress-bearing struts of the main gel network of droplets. More theoretical attention is needed in attractive emulsion systems in order to determine how to analyze DWS MSDs and predict the excess MSDs. Interestingly, these measured excess MSDs can be fit using an empirical modified bound Brownian particle equation that we created to describe these extra fluctuations in the DWS signals. This application of DWS microrheology to attractive emulsions herein serves as a basis from which additional DWS microrheology studies of attractive soft colloidal systems can be performed and analyzed.
Particle tracking microrheology also enables the first study and comparison of the viscosity profiles of bispecific mAbs (BsAb-A/B and BsAb-B/C) and their monospecific counterparts (mAb-A, mAb-B, and mAb-C). The viscosity of mAb-C is higher ...
Author: Lilian Lam Josephson
Particle tracking microrheology also enables the first study and comparison of the viscosity profiles of bispecific mAbs (BsAb-A/B and BsAb-B/C) and their monospecific counterparts (mAb-A, mAb-B, and mAb-C). The viscosity of mAb-C is higher than that of mAb-A, and the Arrhenius mixing rule accurately predicted the mixture of (mAb-A + mAb-C) and the solution of BsAb-A/C. While mAb-A and mAb-B have similar viscosity profiles, their mixture and BsAb-A/B have significantly higher viscosity. Microstructure and protein-protein interactions are examined using light scattering and size exclusion chromatography, and possible mechanisms for the increase in viscosity are discussed.
DEP is one of the promising methods to translate micrometer - sized particles
such as colloidal particles and cells in the micro - fluidic devices , but it has not
been used for microrheology . & is much smaller than the particle size a .
LECTURE X Macro- and Microrheology . Einstein's Law of the Viscosity of Sols . Microrheological Models All developments with which we have dealt so far ,
belong to what may be called macro - rheology . Macrorheology regards all