Nondiffusive Brownian motion studied by diffusing-wave spectroscopy

Weitz, David A.; Pine, David J.; Pusey, P. N.; Tough, R.J.A.

doi:10.1103/physrevlett.63.1747

Cited by 156 publications

(100 citation statements)

References 14 publications

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“…Hinch's theory of Brownian motion takes the hydrodynamic interactions between particles and fluid into account, and it produces the following mean squared displacement [29] Time step corresponding to the adopted jump length of 2 dp (10 2 ) is greater than the particle relaxation time (Θ), as indicated.…”

Section: Appendix: Physical Time Equivalencementioning

confidence: 99%

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Influence of primary-particle density in the morphology of agglomerates

2014

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Agglomeration processes occur in many different realms of science such as colloid and aerosol formation or formation of bacterial colonies. We study the influence of primary particle density in agglomerate structure using diffusion-controlled Monte Carlo simulations with realistic space scales through different regimes (DLA and DLCA). The equivalence of Monte Carlo time steps to real time scales is given by Hirsch's hydrodynamical theory of Brownian motion. Agglomerate behavior at different time stages of the simulations suggests that three indices (fractal exponent, coordination number and eccentricity index) characterize agglomerate geometry. Using these indices, we have found that the initial density of primary particles greatly influences the final structure of the agglomerate as observed in recent experimental works.

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Section: Appendix: Physical Time Equivalencementioning

confidence: 99%

“…The relation between the simulation time step and real time is such that the root mean square displacement of the particle during a time step is 2d p . Then [28] (Appendix 5A), [29] …”

Section: Simulation Detailsmentioning

confidence: 99%

Influence of primary-particle density in the morphology of agglomerates

2014

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“…It applies equally well to both statistically homogeneous and heterogeneous media (media with inclusions, scatterer flows, etc.). Absorption of light, reflection of scattered waves at the sample boundaries, modulation of the source intensity, as well as various types of scatterer motion (Brownian [3,4] and sub-brownian [40] motion, laminar [41][42][43] and turbulent [44] flows, etc.) can be taken into account within the framework of the diffusion model.…”

Section: Introductionmentioning

confidence: 99%

Diffusing-wave spectroscopy of nonergodic media

et al. 2001

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We introduce an elegant method which allows the application of diffusing-wave spectroscopy (DWS) to nonergodic, solidlike samples. The method is based on the idea that light transmitted through a sandwich of two turbid cells can be considered ergodic even though only the second cell is ergodic. If absorption and/or leakage of light take place at the interface between the cells, we establish a so-called "multiplication rule", which relates the intensity autocorrelation function of light transmitted through the double-cell sandwich to the autocorrelation functions of individual cells by a simple multiplication. To test the proposed method, we perform a series of DWS experiments using colloidal gels as model nonergodic media. Our experimental data are consistent with the theoretical predictions, allowing quantitative characterization of nonergodic media and demonstrating the validity of the proposed technique.

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“…we can correct the experimental data using the analytical expression for Newtonian fluids derived by Hinch [22]. In practice we correct the experimental particle mean square displacement: h r 2 t i f t h r 2 t i DWS with f t from [22] and take an initial guess value of eff 3 mPa s from mechanical rheometry data at the highest frequency accessible. Thus we obtain a corrected G !…”

mentioning

confidence: 99%

“…At times shorter than 10 ÿ5 s, or frequencies above ! 10 5 rad=s, inertia effects become sizable [22]. To get access to this interesting ultrahigh frequency regime we introduce a selfconsistent correction scheme for h r 2 t i.…”

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Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

et al. 2007

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We characterize the linear viscoelastic shear properties of an aqueous wormlike micellar solution using diffusing wave spectroscopy (DWS) based tracer microrheology as well as various mechanical techniques such as rotational rheometry, oscillatory squeeze flow, and torsional resonance oscillation covering the frequency range from 10 ÿ1 to 10 6 rad=s. Since DWS as well as mechanical oscillatory squeeze flow and torsional resonance oscillation cover a sufficiently high frequency range, the persistence length of wormlike micelles could be determined directly from rheological measurements for the first time.PACS numbers: 83.80. Qr, 82.70.ÿy, 83.60.Bc, 83.85.Ei Significant progress has been made over the past decade in developing optical microrheology as a noninvasive means to study the rheological properties of soft complex fluids. Following the seminal Letter of Mason and Weitz in 1995 [1], several hundred studies have reported on the application of optical microrheology to such diverse systems as polymers, emulsions, gels, biomaterials, hydrogel scaffolds, stomach mucus, magnetic fluids, ceramics, slurries, and many more [1][2][3][4][5]. The underlying idea is to study the response of small (colloidal) particles embedded in the system under study. The motion of probe particles can either be controlled actively, e.g., using optical tweezers or one can analyze the thermal motion of particles to obtain information about the viscoelastic properties of the surrounding fluid. The latter can be achieved by using diffusing wave spectroscopy (DWS) [6]. DWS provides a fast ensemble average of the tracer motion and can resolve extremely fast displacements on the order of microseconds with subnanometer resolution. Despite the large literature, benchmarking optical microrheological techniques with macroscopic mechanical measurements is still not concluded. Almost all comparisons between microrheology and macrorheology have been restricted to the frequency range <10 2 rad=s due to mechanical limitations and inertial effects in the gap loading limit of conventional rotational rheometers and the limited availability of mechanical devices operating at higher frequencies [7][8][9].Here we apply both DWS and macroscopic mechanical rheometry to characterize an aqueous solution of cetylpyridinium chloride and sodium salicylate (100mM CPyCl-60mM NaSal) at different temperatures. These solutions display complex viscoelastic properties but are easy and reproducible to prepare and stable in time. They exhibit fast dynamics and the structural features are much smaller than the tracer particles. The latter is an important requirement for the successful application of tracer microrheology which might otherwise lead to erroneous results [4]. Because of the peculiar viscoelastic behavior such systems have found wide commercial application ranging from personal care to enhanced oil recovery products [10]. Rapid access to microscopic structural and dynamic properties is therefore of interest both from a fundamental and an applied point of vi...

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Nondiffusive Brownian motion studied by diffusing-wave spectroscopy

Cited by 156 publications

References 14 publications

Influence of primary-particle density in the morphology of agglomerates

Influence of primary-particle density in the morphology of agglomerates

Diffusing-wave spectroscopy of nonergodic media

Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

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